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AA7075 by porthole die at various temperatures
Accepted Manuscript Co-extrusion of dissimilar AA6063/AA7075 by porthole die at various temperatures Jianwei Tang, Liang Chen, Xiangkun Fan, Guoqun Zhao, Cunsheng Zhang PII:
S0925-8388(18)32186-8
DOI:
10.1016/j.jallcom.2018.06.068
Reference:
JALCOM 46404
To appear in:
Journal of Alloys and Compounds
Received Date: 27 March 2018 Revised Date:
5 June 2018
Accepted Date: 6 June 2018
Please cite this article as: J. Tang, L. Chen, X. Fan, G. Zhao, C. Zhang, Co-extrusion of dissimilar AA6063/AA7075 by porthole die at various temperatures, Journal of Alloys and Compounds (2018), doi: 10.1016/j.jallcom.2018.06.068. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Co-extrusion of dissimilar AA6063/AA7075 by porthole die at various temperatures
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Jianwei Tanga, Liang Chena,*, Xiangkun Fana, Guoqun Zhaoa, Cunsheng Zhanga Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of
Education), Shandong University, Jinan, Shandong 250061, PR China.
* Corresponding author:
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Liang Chen
E-mail: [email protected] Tel: +8653181696577
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Fax: +8653188392811
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Associate Professor of Shandong University.
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ACCEPTED MANUSCRIPT Abstract The dissimilar AA6063/AA7075 plate was fabricated by porthole die co-extrusion method, and the effects of extrusion temperature on microstructure and mechanical properties were investigated. The results showed that the sound AA6063/AA7075 welding interface without crack or impurity was
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obtained. Few secondary particles existed in extruded AA6063 side, while large amount of fine particles were found in AA7075 side, and the number of particles was decreased with increasing temperature. The coarse initial grains with the formation of substructures were observed in AA6063. However, the microstructure of AA7075 mainly consisted of fine equiaxed grains with several microns
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due to the occurrence of near complete dynamic recrystallization. The average grains size of the AA6063/AA7075 extruded plate was increased with increasing temperature. The plate extruded at 510 C has strong texture component with 10° shift of Φ from Cube and some weak recrystallization Cube
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texture. The elongation was not affected by temperature, while the hardness and ultimate tensile strength were obviously enhanced with increasing temperature.
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Keywords: Porthole die; Extrusion; Welding interface; Microstructure; Mechanical properties.
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ACCEPTED MANUSCRIPT 1. Introduction Al alloys are the most important lightweight materials due to the advantages of low density, high strength to weight ratio, good corrosion resistance and high surface quality [1-3]. With the increasing demand in environmental protection and energy saving, Al alloys have been widely used in the fields of
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aerospace and automobiles. For instance, various Al alloys have been attempted to replace steel in the body-in-white and some structural components of the automobiles [4-7]. Under this situation, the excellent joint of dissimilar Al alloys has become to an urgent task for researchers and engineers.
The previous studies have proved that friction stir welding (FSW) can join dissimilar alloys with
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good welding quality. Khan et al. [8] successfully fabricated AA7475/AA2219 dissimilar Al alloys by means of FSW, and the obvious grain refinement of the joints was observed. Zheng et al. [9] employed
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FSW to produce lap joints of Al alloy and nickel-base alloy with varied plunge depths, by which the thin Al3Ni interlayer was formed and fine-grained zones were found on both sides of the interface. Luo et al. [10] studied the microstructure evolution of FSWed joints of dissimilar Mg alloys, and a sound joint and a stir zone with fine grains were obtained. Ji et al. [11] obtained a sound joint of AA6061-T6 and AZ31B alloys with smooth surface by means of FSW process assisted with ultrasonic. Thus, it is
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known that FSW process has been widely used to join dissimilar materials. Besides the FSW method, some plastic forming processes were also employed to join dissimilar materials or produce composite plates. In our recent study [12], the porthole die co-extrusion method
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was proposed to join the dissimilar Al alloys. It was found that a sound welding interface was obtained and the microstructure was greatly refined due to the occurrence of dynamic recrystallization (DRX).
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Importantly, the billet for porthole die co-extrusion can be easily prepared, which is beneficial for its engineering application. However, it is noted that the solid welding behavior during porthole die co-extrusion of dissimilar Al alloys is complex, and it might be related to many parameter, such as the billet temperature. Firstly, the flow stress of Al billets is significantly affected by temperature, which further influences the hydrostatic pressure inside welding chamber and the welding quality. Secondly, billet temperature is also an important factor affecting the microstructure such as DRX fraction, grain size and microtexture of the extruded plates. The effects of billet temperature on conventional porthole die extrusion of Al alloys have been well studied based on numerical and experimental works. Liu et al. [13] reported that both the maximum welding pressure and the minimum effective stress decreased with increasing billet 3
ACCEPTED MANUSCRIPT temperature, which means that a sound weld seam can be obtained. Bai et al. [14] studied the welding quality of 6082 Al extruded by porthole die extrusion process, and it was found that the occurrence of local DRX was promoted under higher temperature, which reduced the average grain size inside the welding zone and enhanced the strength of the weld seam. Chen et al. [15] performed experiment using
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7075 Al alloy and found that the billet temperature affected both the welding quality and the microstructure near weld seam.
However, the effects of temperature on the novel porthole die co-extrusion process have not been clarified. In this study, the dissimilar Al-Si-Mg (AA6063) and Al-Zn-Mg (AA7075) alloys were
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attempted to be co-extruded. The great differences in chemical compositions and properties between AA6063 and AA7075 increase the joining difficulty. The experiments were carried out at various
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temperatures of 450 °C, 480 °C and 510 °C. A sound welding interface of dissimilar AA6063/AA7075 without cracks was obtained. Moreover, the effects of temperature on welding interface, microstructure and mechanical properties were carefully investigated. 2. Experimental procedures
The chemical compositions of AA6063 and AA7075 are listed in Table 1. Both alloys were
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fabricated by means of semi-continuous casting process. Then, the as-cast AA6063 was homogenized at 540 oC for 12 hours, and slowly cooled to room temperature in the air. Similarly, the homogenization for as-cast AA7075 was carried out at 530 oC for 20 h. The cylindrical billets for extrusion with the
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dimension of ϕ24×45 mm were machined from the homogenized alloys. As shown in Fig. 1, the extrusion setup mainly consists of container, upper die, and lower die. The container was designed to
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have two cavities with the inner diameter of 24 mm, and the calculated extrusion ratio is around 10.5. The extrusion experiments were carried out using a pressuring machine of 200 t. The experimental temperature was set to be 450 oC, 480 oC and 510 oC, respectively. The ram velocity was kept constant at 0.1 mm/s during the whole extrusion process. Finally, the extruded plate was cooled down to room temperature in the air.
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ACCEPTED MANUSCRIPT Table 1 Chemical compositions (wt.%) of the as-received AA6063 and AA7075. Zn
Mg
Si
Cu
Fe
Mn
Al
AA6063
0.10
0.80
0.45
0.10
0.35
0.10
Bal.
AA7075
5.50
2.35
0.40
1.36
0.40
0.13
Bal.
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Alloy
Fig. 1. Schematic diagram of the extrusion setup, and the location of specimens for microstructure
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observation, hardness and tensile test. (Unit: mm)
As shown in Fig. 1, a plate-shaped profile with the rectangular cross-section of 18×5 mm was extruded, where the width, length and thickness directions of extruded profiles indicate TD, ED and
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ND directions, and the welding interface located in the mid-plane of the plate parallel to ED direction. For convenience, the plates extruded at 450 oC, 480 oC and 510 oC were named as T450, T480 and
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T510, respectively. The grain structure of as-homogenized billets was examined using optical microscope (OM). For OM observation, the specimens were firstly ground and polished, and then AA6063 was etched in the solution of 5.0 ml HF and 95 ml H2O, and AA7075 was etched in the solution of 1.0 ml HF, 1.5 ml HCl, 2.5 ml HNO3 and 95.0 ml H2O. The microstructure of extruded plates was analyzed by means of electron backscatter diffraction (EBSD). For EBSD analysis, the specimens were processed by electro polishing in the solution of 30 ml nitric acid and 70 ml methanol at 12 V for 20 s. Moreover, the secondary phases and welding interface were observed using scanning electron microscope (SEM) after polishing or etching. Due to the limited size of extruded plate, the nonstandard tensile specimens were used, while it should be reasonable for comparing different cases in this study. The tensile specimen was machined parallel with transverse direction (TD), and the 5
ACCEPTED MANUSCRIPT welding interface was located in the middle of the specimen. The main dimension of the tensile specimen is indicated in Fig. 1. The tensile tests were carried out at a constant stretching rate of 0.45 mm/min at room temperature, and the fracture surface was observed by SEM. Vickers micro-hardness was measured at an interval of 200 µm along TD direction using a load of 100 g and dwelling for 8 s.
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3. Results and Discussion 3.1. As-homogenized microstructure
Fig. 2 shows the microstructure of as-homogenized billets. The chemical compositions of some selected points were analyzed using EDS, and the results are listed in Table 2. As is seen in Fig. 2(a)
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and (b), both AA6063 and AA7075 consist of coarse equiaxed grains with an average size around 100 µm. After homogenization treatment of AA6063, few coarse particles can be observed from Fig. 2(c).
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According to the EDS results, these coarse particles should be α-AlFeSi phase, which are difficult to dissolve into Al matrix [16]. On the other hand, since the concentration of alloying element (Zn, Mg and Cu) in AA7075 is much higher, the homogenization is insufficient for the dissolving of all particles, as shown in Fig. 2(d). Thus, it is observed that some coarse particles still exist on the grain boundaries. Moreover, lots of fine particles with needle and granular shape disperses inside the grains. These fine
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particles might be precipitated during the air cooling process after homogenization. According to the EDS results, the coarse particles on the grain boundary consist of Al, Mg, Cu and Fe, which should be Al23CuFe4. However, the fine particles with needle-like and granular shape inside grain contain Al, Zn,
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Mg, and Cu, which should be MgZn2 and Al2CuMg [17-19].
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Fig. 2. Optical and SEM observation of the as-homogenized (a) (c) AA6063 and (b) (d) AA7075.
Table 2 Chemical compositions of the chosen points using EDS analysis. Al
Zn
Si
Points
Cu
Mg
Fe
at.%
wt.%
at.%
wt.%
at.%
wt.%
at.%
wt.%
at.%
wt.%
at.%
1
63.58
74.34
0.00
0.00
9.11
10.24
0.00
0.00
0.00
0.00
27.30
15.42
2
48.07
63.51
0.00
0.00
0.00
0.00
12.61
7.07
5.22
7.65
34.10
21.77
3
46.50
60.27
33.64
18.00
0.00
0.00
7.69
4.23
12.17
17.50
0.00
0.00
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wt.%
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3.2. Welding interface
Fig. 3 shows the SEM images across AA6063/AA7075 welding interface. As is shown, there is no
crack or impurity existing on the welding interface of all extruded plates. During porthole die co-extrusion process, two metal streams firstly move from the porthole to the welding chamber due to the pressure along ED direction. Then, inside the welding chamber, two metal streams move to each other until they meet together. Finally, the contacted metal streams started to be solid bonded due to the pressure along TD direction, and the sound solid bonding can be obtained under the condition of high pressure and high temperature. According to Yu et al. [20], higher temperature and higher welding pressure contribute to the closure of the micro-voids on the welding interface. Moreover, with
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ACCEPTED MANUSCRIPT increasing temperature, the diffusion of alloying atoms were accelerated and higher atomic bonding degree can be achieved on the AA6063/AA7075 interface. Hence, it is expected that T510 plate has
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better welding quality, which is beneficial for the improvement of mechanical properties.
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Fig. 3. SEM micrographs of welding interface and second phase distribution in extruded plates of (a) T450, (b) T480, and (c) T510.
It can also be observed from Fig. 3 that few α-AlFeSi particles exist in AA6063 side, which is
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similar with the as-homogenized AA6063 billet, since α-AlFeSi phase is a stable phase and it is
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difficult to dissolve into Al matrix during extrusion process. However, in comparison with the homogenized AA6063 billet, the number of coarse particles in extruded AA7075 side decreases, while the number of fine particles increases. According to the research of Reti et al. [21], most of the coarse Al23CuFe4 particles in homogenized AA7075 billet can be broken down into fine particles during hot extrusion process. Moreover, at the present extrusion temperatures, the MgZn2 particles in AA7075 billet should be firstly dissolved into Al matrix, and then precipitated again during the extrusion process [17]. On the other hand, with the increase of extrusion temperature, the solubility of alloying elements was enhanced and less particles were precipitated. Thus, it is observed that the amount of fine particles in extruded AA7075 side is reduced with increasing temperature.
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ACCEPTED MANUSCRIPT 3.3. Grain morphology of the extruded plate In order to study the effects of temperature on microstructure of extruded plates, EBSD analysis was conducted in the area across the welding interface. Fig. 4 shows the EBSD maps, where the grey lines indicate low angle grain boundaries (LABs) with the misorientation angle between 2° and 15°,
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and the black lines indicate high angle grain boundaries (HABs) with the misorientation higher than 15°. The left side of the maps is AA6063, and the right side is AA7075. During porthole die extrusion, the initial equiaxed grains are firstly elongated along ED direction under the combined effects of shearing and compressing stress. Then, the elongated grains grow into the strip-shaped grains by means
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of grain boundary migration [22]. Moreover, lots of LABs were formed inside the coarse grains of AA6063, as shown in Fig. 4. According to the previous studies [23-25], with the occurrence of
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dynamic recovery (DRV), the dislocation multiplication rapidly increases resulting in the increase of dislocation density. The dislocation climbs and cross-slips along the slip surface, which leads to the crushing of original grain and the formation substructures with LABs. Importantly, it is also observed that AA7075 exhibits near complete DRXed structure with fine grains of several microns, while the relatively coarse grains were remained in AA6063 after extrusion. It indicates that AA7075 is more
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favorable for the occurrence of DRX than that of AA6063 under the same deformation condition, and
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the reasons are explained as follows.
Fig. 4. EBSD maps of the grain morphology and distribution of low and high angle grain boundaries of (a) T450, (b) T480, and (c) T510.
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ACCEPTED MANUSCRIPT It has been reported that DRV easily occurred in AA7075 during hot deformation because of the high stacking fault energy of Al-Mg-Zn alloy [26]. Thus, during porthole die extrusion, DRV is enhanced and more substructures with LABs are formed in AA7075 in comparison with AA6063. As is known, DRV is accompanied with the increase of dislocation density. Then, the dislocation further
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annihilates and becomes the energy of DRX. Sakai et al. [27] reported that the new DRXed grains in Al-Mg-Zn alloy are formed by the gradual transformation from LABs to HABs due to the accumulation of dislocations at the LABs. The more LABs in AA7075 provide higher energy for the DRX and large amount of LABs transform to HABs, while some amount of LABs were remained
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inside the coarse grains of AA6063 due to insufficient energy for DRX. On the other hand, the second phase particles also play an important role on the DRX behavior of Al alloys. As mentioned above,
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large amount of finely dispersed particles exist in AA7075, while only few coarse particles were found in AA6063. The particles with the size >1 µm can act as the nucleation sites for recrystallization, which is well known as the particle stimulated nucleation (PSN) [28]. Thus, large amount of particles in AA7075 also results in the acceleration of DRX kinetics.
Fig. 5 presents the size distribution of the grains calculated based on the EBSD maps. As is seen,
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with the increase of extrusion temperature, the average grain size is increased. It has been mentioned that the amount of dispersed particles was reduced at higher temperature. Thus, the PSN effect is weakened, and the newly formed DRXed grains should have relative large size. Moreover, the particles
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also have significant effects on grain growth by applying a dragging force on the migration of grain boundary, which is called Zener pinning effect. On the other hand, the growing mobility of DRXed
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grains becomes higher with increasing temperature. All of these reasons result in the fact that T510 plate has larger average grain size.
Fig. 5. Relative frequency of grain size in extruded plates of (a) T450, (b) T480, and (c) T510.
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direction and around <111> on TD direction in T510 can be observed. It indicates that the extrusion
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temperature has significant effects on the concentrated orientation and texture intensity.
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Fig. 6. IPF for the area near welding interface of (a) T450, (b) T480, and (c) T510.
In order to accurately determine the texture components, the orientation distribution function
(ODF) sections of φ2=0°, 45° and 65° of the extruded plates were drawn in Fig. 7. As is shown, the texture of T450 mainly consists of Copper Twin texture and some relative weak Goss. With the increase of extrusion temperature, the texture of T480 contains strong plane-strain texture components of Copper and some other weak components. The texture of T510 consists of strong component with 10° shift of Φ from Cube and some relative weak recrystallization Cube texture. As reported by Hamad et al. [29], the rolling texture components such as Copper and Copper Twin in Al alloys are characterized by the development of preferred orientations along β-fibers. However, in T510 plate, the
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ACCEPTED MANUSCRIPT ODF result reveals a significant increase in the intensity of Cube components as the grain coarsening was promoted, while the intensity of rolling components was obviously decreased. This phenomenon reflected that the grains with rolling texture orientation have lower thermal stability than those with recrystallization texture orientation, such as Cube. Thus, the rolling texture might transform to
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recrystallization texture with grain coarsening at higher temperature.
Fig. 7. The ODF sections of the extruded plates of (a) T450, (b) T480, and (c) T510.
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3.5. Mechanical properties and fracture morphology The micro-hardness tests were conducted along a line perpendicular to AA6063/AA7075 welding
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interface, and the results are plotted in Fig. 8. As is shown, the hardness of AA7075 matrix is much higher than that of AA6063 matrix, while the hardness on the welding interface is always between them, which indicates that the atom diffusion occurred across the AA6063/AA7075 interface. The indentation size gradually decreases from AA6063 to AA7075, which also proves the above mentioned tendency. Moreover, T510 plate exhibits higher hardness in AA6063, AA7075 and also the interface than that of T450 and T480 plates. It has been mentioned in Fig. 5 that the average grain size increases with increasing temperature, and the hardness should be lower in case of plate T510. However, the opposite tendency of hardness was observed. It suggests that the average grain size is not the only factor that affects the hardness of the extruded plates. As reported by Zhan et al. [30], severe deformation can
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ACCEPTED MANUSCRIPT result in serious distortion of grains, which has harmful effects on its stability of compression resistance and the hardness could be reduced. The flow stress of Al alloys is usually sensitive to the deformation temperature, which means lower temperature can generate higher flow stress. Thus, when the extrusion was performed at 450 oC and 480 oC, the deformation for T450 and T480 should be more severe than
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that of T510, which results in the higher hardness of T510. Moreover, it has been mentioned that the amount of secondary particles in T510 plate is reduced, which means that more alloying elements were dissolved into the Al matrix. Thus, another possible reason for the high hardness of T510 might be that
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the solution strengthening effect is more effective than the particle strengthening effect in this study.
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Fig. 8. Hardness distribution of the extruded AA6063/AA7075 dissimilar Al plates.
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Fig. 9 shows the results obtained from tensile tests. The ultimate tensile strength of T450, T480, and T510 are 129±3 MPa, 138±3 MPa, and 166±2 MPa, respectively, which indicates that the strength increases with increasing temperature. However, the effect of extrusion temperature on elongation is slight, and all extruded plates exhibit high value of elongation percentage around 0.29. Generally, the mechanical properties of the alloy extruded by porthole die extrusion are determined by both the microstructure and welding quality. In this study, the extrusion temperature has relative weak effects on the microstructure of all three plates based on the above discussion. Thus, the difference in mechanical properties along TD direction should be the result of varied welding quality. Firstly, the increase of extrusion temperature results in higher ratio of welding pressure to material’s flow stress inside welding chamber [31]. This ratio can be used to evaluate the welding quality, and higher ratio means good 13
ACCEPTED MANUSCRIPT bonding degree. Secondly, the existence of the strip-shaped grains is adverse for the welding quality [22]. As shown in Fig. 4, T450 and T480 plates have more strip-shaped grains, while the grains in T510 are relative uniform resulting in the improvement of welding quality. Thirdly, the texture types and its intensity also have great effects on the final mechanical properties [32]. Due to these combined effects,
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the tensile properties of AA6063/AA7075 plates fabricated by porthole die co-extrusion were enhanced
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at higher temperature.
Fig. 9. Tensile properties of the extruded AA6063/AA7075 dissimilar Al plates.
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Fig. 10 shows the fracture morphologies of specimens after tensile tests. The fracture surfaces of all plates exhibit both ductile and brittle fractures, where the former was characterized by dimples and the latter has a feature of smooth surface with few shallow dimples [33]. As is seen, many dimples exist
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in the fracture surfaces of all specimens, which indicates good ductility. However, the number and depth of dimples vary obviously. As for T450 and T480 plates extruded at lower temperature, they have
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relatively fewer and shallower dimples, and some smooth flat facets which denote bad mechanical properties can be observed. T510 plate exhibits fewer smooth flat facets with more and deeper dimples than that of T450 and T480, which indicates the ductile fracture morphology. The results of fracture morphologies agree well with the tensile test results shown in Fig. 9.
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Fig. 10. SEM observation of the fracture morphology of (a) T450, (b) T480, and (c) T510.
4. Conclusions
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In this study, the effects of extrusion temperature on microstructure and mechanical properties of the AA6063/AA7075 plates extruded by porthole die was studied. Based on the experimental results, the main results and conclusions are summarized as follows.
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(1) The sound AA6063/AA7075 welding interface without crack or impurity was obtained by means of porthole die co-extrusion. Few secondary particles exist in extruded AA6063 side. However,
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large amounts of fine particles were found in AA7075 side, and the number of particles was decreased with increasing temperature. (2) After extrusion process, AA7075 exhibits high DRX fraction, and the microstructure consists
of fine equiaxed grains with several microns. In AA6063, the coarse initial grains were remained and elongated along ED direction, and the substructures with LABs were formed inside the coarse grains. Moreover, the average grains size was increased with increasing temperature. (3) The temperature significantly affects the texture types and intensities. The extruded T450 plate consists of Copper Twin and some weak Goss. T480 plate contains strong plane-strain texture component of Copper and other weak components. For T510 plate, strong texture component with 10° shift of Φ from Cube and some weak recrystallization texture Cube were observed. 15
ACCEPTED MANUSCRIPT (4) The hardness increases with increasing extrusion temperature in AA6063, AA7075, and AA6063/AA7075 interface. The elongation was not affected by temperature, while the ultimate tensile strength was obviously enhanced at higher temperature.
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Acknowledgements The authors would like to acknowledge the financial support from National Natural Science Foundation of China (U1708251), Key Research and Development Program of Shandong Province
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(2018GGX103041), and China Postdoctoral Science Foundation (2017M622194 and 2018T110686).
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ACCEPTED MANUSCRIPT [20] J. Yu, G. Zhao, W. Cui, C. Zhang, L. Chen, Microstructural evolution and mechanical properties of welding seams in aluminum alloy profiles extruded by a porthole die under different billet heating temperatures and extrusion speeds, J. Mater. Process. Technol., 247 (2017) 214-222. [21] A.M. Reti, M.C. Flemings, Solution kinetics of two wrought aluminum alloys. Metall. Mater.
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Trans. B, 3(7) (1972) 1869-1875. [22] J. Yu, G. Zhao, C. Zhang, L. Chen, Dynamic evolution of grain structure and micro-texture along a welding path of aluminum alloy profiles extruded by porthole dies, Mater. Sci. Eng. A, 682 (2017) 679-690.
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[23] L. Li, G. Wang, J. Liu, Z. Yao, Flow softening behavior and microstructure evolution of Al-5Zn-2Mg aluminum alloy during dynamic recovery, Trans. Nonferrous Met. Soc. China, 24 (2014)
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[24] J.F. Xie, Y.L. Zhu, F.L. Bian, C. Liu, Dynamic recovery and recrystallization mechanisms during ultrasonic spot welding of Al-Cu-Mg alloy, Mater. Charact., 132 (2017) 145-155. [25] P.W. Li, H.Z. Li, L. Huang, X.P. Liang, Z.X. Zhu, Characterization of hot deformation behavior of AA2014 forging aluminum alloy using processing map, Trans. Nonferrous Met. Soc. China, 27 (2017)
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1677-1688.
[26] H.E. Hu, L. Zhen, B.Y. Zhang, L. Yang, J.Z. Chen, Microstructure characterization of 7050 aluminum alloy during dynamic recrystallization and dynamic recovery, Mater. Charact., 59 (2008)
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1185-1189.
[27] T. Sakai, H. Miura, A. Goloborodko, O. Sitdikov, Continuous dynamic recrystallization during the
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transient severe deformation of aluminum alloy 7475, Acta. Mater., 57 (2009) 153-162. [28] K. Huang, K. Marthinsen, Q. Zhao, R.E. Logé, The double-edge effect of second-phase particles on the recrystallization behavior and associated mechanical properties of metallic materials. Prog. Mater. Sci., 92 (2018) 284-359. [29] K. Hamad, H.W. Yang, Y.G. Ko, Interpretation of annealing texture changes of severely deformed Al-Mg-Si alloy, J. Alloys Compd., 687 (2016) 300-305. [30] M. Zhan, X. Wang, H. Long, Mechanism of grain refinement of aluminium alloy in shear spinning under different deviation ratios, Mater. Des., 108 (2016) 207-216. [31] H.H. Jo, S.K. Lee, S.B. Lee, B.M. Kim, Prediction of welding pressure in the non-steady state porthole die extrusion of Al7003 tubes, Int. J. Mach. Tool. Manu., 22 (2002) 753-759. 18
ACCEPTED MANUSCRIPT [32] Q. Wang, B. Jiang, Y. Chai, B. Liu, S. Ma, J. Xu, F. Pan, Tailoring the textures and mechanical properties of AZ31 alloy sheets using asymmetric composite extrusion, Mater. Sci. Eng. A, 673 (2016) 606-615. [33] R.T. Huang, W.L. H., R.H. Huang, L.W. Tsay, Effects of microstructures on the notch tensile
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fracture feature of heat–treated Ti-6Al-6V-2Sn alloy, Mater. Sci. Eng. A, 595 (2014) 297-305.
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Highlights Dissimilar AA6063/AA7075 with sound interface was co-extruded by porthole die.
2)
AA7075 was obviously refined, while large grains were remained in AA6063.
3)
The types and intensities of texture were greatly affected by temperature.
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Hardness and tensile strength were enhanced with increasing temperature.
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S0925-8388(18)32186-8
DOI:
10.1016/j.jallcom.2018.06.068
Reference:
JALCOM 46404
To appear in:
Journal of Alloys and Compounds
Received Date: 27 March 2018 Revised Date:
5 June 2018
Accepted Date: 6 June 2018
Please cite this article as: J. Tang, L. Chen, X. Fan, G. Zhao, C. Zhang, Co-extrusion of dissimilar AA6063/AA7075 by porthole die at various temperatures, Journal of Alloys and Compounds (2018), doi: 10.1016/j.jallcom.2018.06.068. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Co-extrusion of dissimilar AA6063/AA7075 by porthole die at various temperatures
a
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Jianwei Tanga, Liang Chena,*, Xiangkun Fana, Guoqun Zhaoa, Cunsheng Zhanga Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of
Education), Shandong University, Jinan, Shandong 250061, PR China.
* Corresponding author:
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Liang Chen
E-mail: [email protected] Tel: +8653181696577
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Fax: +8653188392811
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Associate Professor of Shandong University.
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ACCEPTED MANUSCRIPT Abstract The dissimilar AA6063/AA7075 plate was fabricated by porthole die co-extrusion method, and the effects of extrusion temperature on microstructure and mechanical properties were investigated. The results showed that the sound AA6063/AA7075 welding interface without crack or impurity was
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obtained. Few secondary particles existed in extruded AA6063 side, while large amount of fine particles were found in AA7075 side, and the number of particles was decreased with increasing temperature. The coarse initial grains with the formation of substructures were observed in AA6063. However, the microstructure of AA7075 mainly consisted of fine equiaxed grains with several microns
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due to the occurrence of near complete dynamic recrystallization. The average grains size of the AA6063/AA7075 extruded plate was increased with increasing temperature. The plate extruded at 510 C has strong texture component with 10° shift of Φ from Cube and some weak recrystallization Cube
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texture. The elongation was not affected by temperature, while the hardness and ultimate tensile strength were obviously enhanced with increasing temperature.
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Keywords: Porthole die; Extrusion; Welding interface; Microstructure; Mechanical properties.
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ACCEPTED MANUSCRIPT 1. Introduction Al alloys are the most important lightweight materials due to the advantages of low density, high strength to weight ratio, good corrosion resistance and high surface quality [1-3]. With the increasing demand in environmental protection and energy saving, Al alloys have been widely used in the fields of
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aerospace and automobiles. For instance, various Al alloys have been attempted to replace steel in the body-in-white and some structural components of the automobiles [4-7]. Under this situation, the excellent joint of dissimilar Al alloys has become to an urgent task for researchers and engineers.
The previous studies have proved that friction stir welding (FSW) can join dissimilar alloys with
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good welding quality. Khan et al. [8] successfully fabricated AA7475/AA2219 dissimilar Al alloys by means of FSW, and the obvious grain refinement of the joints was observed. Zheng et al. [9] employed
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FSW to produce lap joints of Al alloy and nickel-base alloy with varied plunge depths, by which the thin Al3Ni interlayer was formed and fine-grained zones were found on both sides of the interface. Luo et al. [10] studied the microstructure evolution of FSWed joints of dissimilar Mg alloys, and a sound joint and a stir zone with fine grains were obtained. Ji et al. [11] obtained a sound joint of AA6061-T6 and AZ31B alloys with smooth surface by means of FSW process assisted with ultrasonic. Thus, it is
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known that FSW process has been widely used to join dissimilar materials. Besides the FSW method, some plastic forming processes were also employed to join dissimilar materials or produce composite plates. In our recent study [12], the porthole die co-extrusion method
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was proposed to join the dissimilar Al alloys. It was found that a sound welding interface was obtained and the microstructure was greatly refined due to the occurrence of dynamic recrystallization (DRX).
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Importantly, the billet for porthole die co-extrusion can be easily prepared, which is beneficial for its engineering application. However, it is noted that the solid welding behavior during porthole die co-extrusion of dissimilar Al alloys is complex, and it might be related to many parameter, such as the billet temperature. Firstly, the flow stress of Al billets is significantly affected by temperature, which further influences the hydrostatic pressure inside welding chamber and the welding quality. Secondly, billet temperature is also an important factor affecting the microstructure such as DRX fraction, grain size and microtexture of the extruded plates. The effects of billet temperature on conventional porthole die extrusion of Al alloys have been well studied based on numerical and experimental works. Liu et al. [13] reported that both the maximum welding pressure and the minimum effective stress decreased with increasing billet 3
ACCEPTED MANUSCRIPT temperature, which means that a sound weld seam can be obtained. Bai et al. [14] studied the welding quality of 6082 Al extruded by porthole die extrusion process, and it was found that the occurrence of local DRX was promoted under higher temperature, which reduced the average grain size inside the welding zone and enhanced the strength of the weld seam. Chen et al. [15] performed experiment using
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7075 Al alloy and found that the billet temperature affected both the welding quality and the microstructure near weld seam.
However, the effects of temperature on the novel porthole die co-extrusion process have not been clarified. In this study, the dissimilar Al-Si-Mg (AA6063) and Al-Zn-Mg (AA7075) alloys were
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attempted to be co-extruded. The great differences in chemical compositions and properties between AA6063 and AA7075 increase the joining difficulty. The experiments were carried out at various
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temperatures of 450 °C, 480 °C and 510 °C. A sound welding interface of dissimilar AA6063/AA7075 without cracks was obtained. Moreover, the effects of temperature on welding interface, microstructure and mechanical properties were carefully investigated. 2. Experimental procedures
The chemical compositions of AA6063 and AA7075 are listed in Table 1. Both alloys were
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fabricated by means of semi-continuous casting process. Then, the as-cast AA6063 was homogenized at 540 oC for 12 hours, and slowly cooled to room temperature in the air. Similarly, the homogenization for as-cast AA7075 was carried out at 530 oC for 20 h. The cylindrical billets for extrusion with the
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dimension of ϕ24×45 mm were machined from the homogenized alloys. As shown in Fig. 1, the extrusion setup mainly consists of container, upper die, and lower die. The container was designed to
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have two cavities with the inner diameter of 24 mm, and the calculated extrusion ratio is around 10.5. The extrusion experiments were carried out using a pressuring machine of 200 t. The experimental temperature was set to be 450 oC, 480 oC and 510 oC, respectively. The ram velocity was kept constant at 0.1 mm/s during the whole extrusion process. Finally, the extruded plate was cooled down to room temperature in the air.
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ACCEPTED MANUSCRIPT Table 1 Chemical compositions (wt.%) of the as-received AA6063 and AA7075. Zn
Mg
Si
Cu
Fe
Mn
Al
AA6063
0.10
0.80
0.45
0.10
0.35
0.10
Bal.
AA7075
5.50
2.35
0.40
1.36
0.40
0.13
Bal.
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Alloy
Fig. 1. Schematic diagram of the extrusion setup, and the location of specimens for microstructure
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observation, hardness and tensile test. (Unit: mm)
As shown in Fig. 1, a plate-shaped profile with the rectangular cross-section of 18×5 mm was extruded, where the width, length and thickness directions of extruded profiles indicate TD, ED and
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ND directions, and the welding interface located in the mid-plane of the plate parallel to ED direction. For convenience, the plates extruded at 450 oC, 480 oC and 510 oC were named as T450, T480 and
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T510, respectively. The grain structure of as-homogenized billets was examined using optical microscope (OM). For OM observation, the specimens were firstly ground and polished, and then AA6063 was etched in the solution of 5.0 ml HF and 95 ml H2O, and AA7075 was etched in the solution of 1.0 ml HF, 1.5 ml HCl, 2.5 ml HNO3 and 95.0 ml H2O. The microstructure of extruded plates was analyzed by means of electron backscatter diffraction (EBSD). For EBSD analysis, the specimens were processed by electro polishing in the solution of 30 ml nitric acid and 70 ml methanol at 12 V for 20 s. Moreover, the secondary phases and welding interface were observed using scanning electron microscope (SEM) after polishing or etching. Due to the limited size of extruded plate, the nonstandard tensile specimens were used, while it should be reasonable for comparing different cases in this study. The tensile specimen was machined parallel with transverse direction (TD), and the 5
ACCEPTED MANUSCRIPT welding interface was located in the middle of the specimen. The main dimension of the tensile specimen is indicated in Fig. 1. The tensile tests were carried out at a constant stretching rate of 0.45 mm/min at room temperature, and the fracture surface was observed by SEM. Vickers micro-hardness was measured at an interval of 200 µm along TD direction using a load of 100 g and dwelling for 8 s.
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3. Results and Discussion 3.1. As-homogenized microstructure
Fig. 2 shows the microstructure of as-homogenized billets. The chemical compositions of some selected points were analyzed using EDS, and the results are listed in Table 2. As is seen in Fig. 2(a)
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and (b), both AA6063 and AA7075 consist of coarse equiaxed grains with an average size around 100 µm. After homogenization treatment of AA6063, few coarse particles can be observed from Fig. 2(c).
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According to the EDS results, these coarse particles should be α-AlFeSi phase, which are difficult to dissolve into Al matrix [16]. On the other hand, since the concentration of alloying element (Zn, Mg and Cu) in AA7075 is much higher, the homogenization is insufficient for the dissolving of all particles, as shown in Fig. 2(d). Thus, it is observed that some coarse particles still exist on the grain boundaries. Moreover, lots of fine particles with needle and granular shape disperses inside the grains. These fine
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particles might be precipitated during the air cooling process after homogenization. According to the EDS results, the coarse particles on the grain boundary consist of Al, Mg, Cu and Fe, which should be Al23CuFe4. However, the fine particles with needle-like and granular shape inside grain contain Al, Zn,
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Mg, and Cu, which should be MgZn2 and Al2CuMg [17-19].
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Fig. 2. Optical and SEM observation of the as-homogenized (a) (c) AA6063 and (b) (d) AA7075.
Table 2 Chemical compositions of the chosen points using EDS analysis. Al
Zn
Si
Points
Cu
Mg
Fe
at.%
wt.%
at.%
wt.%
at.%
wt.%
at.%
wt.%
at.%
wt.%
at.%
1
63.58
74.34
0.00
0.00
9.11
10.24
0.00
0.00
0.00
0.00
27.30
15.42
2
48.07
63.51
0.00
0.00
0.00
0.00
12.61
7.07
5.22
7.65
34.10
21.77
3
46.50
60.27
33.64
18.00
0.00
0.00
7.69
4.23
12.17
17.50
0.00
0.00
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3.2. Welding interface
Fig. 3 shows the SEM images across AA6063/AA7075 welding interface. As is shown, there is no
crack or impurity existing on the welding interface of all extruded plates. During porthole die co-extrusion process, two metal streams firstly move from the porthole to the welding chamber due to the pressure along ED direction. Then, inside the welding chamber, two metal streams move to each other until they meet together. Finally, the contacted metal streams started to be solid bonded due to the pressure along TD direction, and the sound solid bonding can be obtained under the condition of high pressure and high temperature. According to Yu et al. [20], higher temperature and higher welding pressure contribute to the closure of the micro-voids on the welding interface. Moreover, with
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ACCEPTED MANUSCRIPT increasing temperature, the diffusion of alloying atoms were accelerated and higher atomic bonding degree can be achieved on the AA6063/AA7075 interface. Hence, it is expected that T510 plate has
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better welding quality, which is beneficial for the improvement of mechanical properties.
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Fig. 3. SEM micrographs of welding interface and second phase distribution in extruded plates of (a) T450, (b) T480, and (c) T510.
It can also be observed from Fig. 3 that few α-AlFeSi particles exist in AA6063 side, which is
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similar with the as-homogenized AA6063 billet, since α-AlFeSi phase is a stable phase and it is
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difficult to dissolve into Al matrix during extrusion process. However, in comparison with the homogenized AA6063 billet, the number of coarse particles in extruded AA7075 side decreases, while the number of fine particles increases. According to the research of Reti et al. [21], most of the coarse Al23CuFe4 particles in homogenized AA7075 billet can be broken down into fine particles during hot extrusion process. Moreover, at the present extrusion temperatures, the MgZn2 particles in AA7075 billet should be firstly dissolved into Al matrix, and then precipitated again during the extrusion process [17]. On the other hand, with the increase of extrusion temperature, the solubility of alloying elements was enhanced and less particles were precipitated. Thus, it is observed that the amount of fine particles in extruded AA7075 side is reduced with increasing temperature.
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ACCEPTED MANUSCRIPT 3.3. Grain morphology of the extruded plate In order to study the effects of temperature on microstructure of extruded plates, EBSD analysis was conducted in the area across the welding interface. Fig. 4 shows the EBSD maps, where the grey lines indicate low angle grain boundaries (LABs) with the misorientation angle between 2° and 15°,
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and the black lines indicate high angle grain boundaries (HABs) with the misorientation higher than 15°. The left side of the maps is AA6063, and the right side is AA7075. During porthole die extrusion, the initial equiaxed grains are firstly elongated along ED direction under the combined effects of shearing and compressing stress. Then, the elongated grains grow into the strip-shaped grains by means
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of grain boundary migration [22]. Moreover, lots of LABs were formed inside the coarse grains of AA6063, as shown in Fig. 4. According to the previous studies [23-25], with the occurrence of
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dynamic recovery (DRV), the dislocation multiplication rapidly increases resulting in the increase of dislocation density. The dislocation climbs and cross-slips along the slip surface, which leads to the crushing of original grain and the formation substructures with LABs. Importantly, it is also observed that AA7075 exhibits near complete DRXed structure with fine grains of several microns, while the relatively coarse grains were remained in AA6063 after extrusion. It indicates that AA7075 is more
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favorable for the occurrence of DRX than that of AA6063 under the same deformation condition, and
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the reasons are explained as follows.
Fig. 4. EBSD maps of the grain morphology and distribution of low and high angle grain boundaries of (a) T450, (b) T480, and (c) T510.
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ACCEPTED MANUSCRIPT It has been reported that DRV easily occurred in AA7075 during hot deformation because of the high stacking fault energy of Al-Mg-Zn alloy [26]. Thus, during porthole die extrusion, DRV is enhanced and more substructures with LABs are formed in AA7075 in comparison with AA6063. As is known, DRV is accompanied with the increase of dislocation density. Then, the dislocation further
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annihilates and becomes the energy of DRX. Sakai et al. [27] reported that the new DRXed grains in Al-Mg-Zn alloy are formed by the gradual transformation from LABs to HABs due to the accumulation of dislocations at the LABs. The more LABs in AA7075 provide higher energy for the DRX and large amount of LABs transform to HABs, while some amount of LABs were remained
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inside the coarse grains of AA6063 due to insufficient energy for DRX. On the other hand, the second phase particles also play an important role on the DRX behavior of Al alloys. As mentioned above,
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large amount of finely dispersed particles exist in AA7075, while only few coarse particles were found in AA6063. The particles with the size >1 µm can act as the nucleation sites for recrystallization, which is well known as the particle stimulated nucleation (PSN) [28]. Thus, large amount of particles in AA7075 also results in the acceleration of DRX kinetics.
Fig. 5 presents the size distribution of the grains calculated based on the EBSD maps. As is seen,
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with the increase of extrusion temperature, the average grain size is increased. It has been mentioned that the amount of dispersed particles was reduced at higher temperature. Thus, the PSN effect is weakened, and the newly formed DRXed grains should have relative large size. Moreover, the particles
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also have significant effects on grain growth by applying a dragging force on the migration of grain boundary, which is called Zener pinning effect. On the other hand, the growing mobility of DRXed
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grains becomes higher with increasing temperature. All of these reasons result in the fact that T510 plate has larger average grain size.
Fig. 5. Relative frequency of grain size in extruded plates of (a) T450, (b) T480, and (c) T510.
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direction and around <111> on TD direction in T510 can be observed. It indicates that the extrusion
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temperature has significant effects on the concentrated orientation and texture intensity.
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Fig. 6. IPF for the area near welding interface of (a) T450, (b) T480, and (c) T510.
In order to accurately determine the texture components, the orientation distribution function
(ODF) sections of φ2=0°, 45° and 65° of the extruded plates were drawn in Fig. 7. As is shown, the texture of T450 mainly consists of Copper Twin texture and some relative weak Goss. With the increase of extrusion temperature, the texture of T480 contains strong plane-strain texture components of Copper and some other weak components. The texture of T510 consists of strong component with 10° shift of Φ from Cube and some relative weak recrystallization Cube texture. As reported by Hamad et al. [29], the rolling texture components such as Copper and Copper Twin in Al alloys are characterized by the development of preferred orientations along β-fibers. However, in T510 plate, the
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ACCEPTED MANUSCRIPT ODF result reveals a significant increase in the intensity of Cube components as the grain coarsening was promoted, while the intensity of rolling components was obviously decreased. This phenomenon reflected that the grains with rolling texture orientation have lower thermal stability than those with recrystallization texture orientation, such as Cube. Thus, the rolling texture might transform to
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recrystallization texture with grain coarsening at higher temperature.
Fig. 7. The ODF sections of the extruded plates of (a) T450, (b) T480, and (c) T510.
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3.5. Mechanical properties and fracture morphology The micro-hardness tests were conducted along a line perpendicular to AA6063/AA7075 welding
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interface, and the results are plotted in Fig. 8. As is shown, the hardness of AA7075 matrix is much higher than that of AA6063 matrix, while the hardness on the welding interface is always between them, which indicates that the atom diffusion occurred across the AA6063/AA7075 interface. The indentation size gradually decreases from AA6063 to AA7075, which also proves the above mentioned tendency. Moreover, T510 plate exhibits higher hardness in AA6063, AA7075 and also the interface than that of T450 and T480 plates. It has been mentioned in Fig. 5 that the average grain size increases with increasing temperature, and the hardness should be lower in case of plate T510. However, the opposite tendency of hardness was observed. It suggests that the average grain size is not the only factor that affects the hardness of the extruded plates. As reported by Zhan et al. [30], severe deformation can
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ACCEPTED MANUSCRIPT result in serious distortion of grains, which has harmful effects on its stability of compression resistance and the hardness could be reduced. The flow stress of Al alloys is usually sensitive to the deformation temperature, which means lower temperature can generate higher flow stress. Thus, when the extrusion was performed at 450 oC and 480 oC, the deformation for T450 and T480 should be more severe than
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that of T510, which results in the higher hardness of T510. Moreover, it has been mentioned that the amount of secondary particles in T510 plate is reduced, which means that more alloying elements were dissolved into the Al matrix. Thus, another possible reason for the high hardness of T510 might be that
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the solution strengthening effect is more effective than the particle strengthening effect in this study.
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Fig. 8. Hardness distribution of the extruded AA6063/AA7075 dissimilar Al plates.
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Fig. 9 shows the results obtained from tensile tests. The ultimate tensile strength of T450, T480, and T510 are 129±3 MPa, 138±3 MPa, and 166±2 MPa, respectively, which indicates that the strength increases with increasing temperature. However, the effect of extrusion temperature on elongation is slight, and all extruded plates exhibit high value of elongation percentage around 0.29. Generally, the mechanical properties of the alloy extruded by porthole die extrusion are determined by both the microstructure and welding quality. In this study, the extrusion temperature has relative weak effects on the microstructure of all three plates based on the above discussion. Thus, the difference in mechanical properties along TD direction should be the result of varied welding quality. Firstly, the increase of extrusion temperature results in higher ratio of welding pressure to material’s flow stress inside welding chamber [31]. This ratio can be used to evaluate the welding quality, and higher ratio means good 13
ACCEPTED MANUSCRIPT bonding degree. Secondly, the existence of the strip-shaped grains is adverse for the welding quality [22]. As shown in Fig. 4, T450 and T480 plates have more strip-shaped grains, while the grains in T510 are relative uniform resulting in the improvement of welding quality. Thirdly, the texture types and its intensity also have great effects on the final mechanical properties [32]. Due to these combined effects,
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the tensile properties of AA6063/AA7075 plates fabricated by porthole die co-extrusion were enhanced
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Fig. 9. Tensile properties of the extruded AA6063/AA7075 dissimilar Al plates.
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Fig. 10 shows the fracture morphologies of specimens after tensile tests. The fracture surfaces of all plates exhibit both ductile and brittle fractures, where the former was characterized by dimples and the latter has a feature of smooth surface with few shallow dimples [33]. As is seen, many dimples exist
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in the fracture surfaces of all specimens, which indicates good ductility. However, the number and depth of dimples vary obviously. As for T450 and T480 plates extruded at lower temperature, they have
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relatively fewer and shallower dimples, and some smooth flat facets which denote bad mechanical properties can be observed. T510 plate exhibits fewer smooth flat facets with more and deeper dimples than that of T450 and T480, which indicates the ductile fracture morphology. The results of fracture morphologies agree well with the tensile test results shown in Fig. 9.
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Fig. 10. SEM observation of the fracture morphology of (a) T450, (b) T480, and (c) T510.
4. Conclusions
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In this study, the effects of extrusion temperature on microstructure and mechanical properties of the AA6063/AA7075 plates extruded by porthole die was studied. Based on the experimental results, the main results and conclusions are summarized as follows.
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(1) The sound AA6063/AA7075 welding interface without crack or impurity was obtained by means of porthole die co-extrusion. Few secondary particles exist in extruded AA6063 side. However,
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large amounts of fine particles were found in AA7075 side, and the number of particles was decreased with increasing temperature. (2) After extrusion process, AA7075 exhibits high DRX fraction, and the microstructure consists
of fine equiaxed grains with several microns. In AA6063, the coarse initial grains were remained and elongated along ED direction, and the substructures with LABs were formed inside the coarse grains. Moreover, the average grains size was increased with increasing temperature. (3) The temperature significantly affects the texture types and intensities. The extruded T450 plate consists of Copper Twin and some weak Goss. T480 plate contains strong plane-strain texture component of Copper and other weak components. For T510 plate, strong texture component with 10° shift of Φ from Cube and some weak recrystallization texture Cube were observed. 15
ACCEPTED MANUSCRIPT (4) The hardness increases with increasing extrusion temperature in AA6063, AA7075, and AA6063/AA7075 interface. The elongation was not affected by temperature, while the ultimate tensile strength was obviously enhanced at higher temperature.
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Acknowledgements The authors would like to acknowledge the financial support from National Natural Science Foundation of China (U1708251), Key Research and Development Program of Shandong Province
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(2018GGX103041), and China Postdoctoral Science Foundation (2017M622194 and 2018T110686).
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ACCEPTED MANUSCRIPT J. Alloys Compd., 695 (2017) 2902-2908. [9] Q. Zheng, X. Feng, Y. Shen, G. Huang, P. Zhao, Effect of plunge depth on microstructure and mechanical properties of FSW lap joint between aluminum alloy and nickel-base alloy, J. Alloys Compd., 695 (2017) 952-961.
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ACCEPTED MANUSCRIPT [20] J. Yu, G. Zhao, W. Cui, C. Zhang, L. Chen, Microstructural evolution and mechanical properties of welding seams in aluminum alloy profiles extruded by a porthole die under different billet heating temperatures and extrusion speeds, J. Mater. Process. Technol., 247 (2017) 214-222. [21] A.M. Reti, M.C. Flemings, Solution kinetics of two wrought aluminum alloys. Metall. Mater.
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ACCEPTED MANUSCRIPT [32] Q. Wang, B. Jiang, Y. Chai, B. Liu, S. Ma, J. Xu, F. Pan, Tailoring the textures and mechanical properties of AZ31 alloy sheets using asymmetric composite extrusion, Mater. Sci. Eng. A, 673 (2016) 606-615. [33] R.T. Huang, W.L. H., R.H. Huang, L.W. Tsay, Effects of microstructures on the notch tensile
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fracture feature of heat–treated Ti-6Al-6V-2Sn alloy, Mater. Sci. Eng. A, 595 (2014) 297-305.
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Highlights Dissimilar AA6063/AA7075 with sound interface was co-extruded by porthole die.
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AA7075 was obviously refined, while large grains were remained in AA6063.
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The types and intensities of texture were greatly affected by temperature.
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Hardness and tensile strength were enhanced with increasing temperature.
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