- Email: [email protected]
copper by accumulative roll bonding (ARB) process
Journal of Manufacturing Processes 46 (2019) 298–303
Contents lists available at ScienceDirect
Journal of Manufacturing Processes journal homepage: www.elsevier.com/locate/manpro
Producing multi-layer composite of stainless steel/aluminum/copper by accumulative roll bonding (ARB) process ⁎
Hamidreza Mansouria, , Beitallah Eghbalia, Masoud Afrandb,c,
T
⁎
a
Materials Engineering Faculty, Sahand University of Technology, Tabriz, Iran Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam c Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam b
A R T I C LE I N FO
A B S T R A C T
Keywords: Severe plastic deformation Accumulative roll bonding (ARB) Multi-layered composite Intermetallic compound
Mechanical process of Accumulative Roll Bonding (ARB) is one of the severe plastic deformation methods which can be contributed to produce ultrafine grind composites. In this research, multi-layered composite of stainless steel/aluminum/copper after five cycles of accumulative roll bonding has been produced. In order to examine the microstructure of the sample during the process of ARB, images of optical microscope (OM), and scanning electron microscope (SEM) of sample cross section were provided. Moreover, inter-diffusion of atoms of Steel, Al, and Cu has been examined through linear elemental analysis. In order for recognition of created phases in composite, X-Ray diffraction analysis (XRD) has been done. At the end, a test of hardness has been done on various layers of composite. The results showed that in the first and second cycle of the ARB, it has not been created any plastic instability in the layers. By increasing the number of the cycle of accumulative roll bonding up to the five, plastic instability (necking and fracturing) will be observed. According to the result of this study, during the process of ARB, proper connection has been created among the layers. By increasing the cycles up to the five, a composite of aluminum matrix, grinds reinforcing Cu, and steel will be produced. In addition, the investigation of atomic diffusion indicates that the diffusion of the atoms of Cu and Al is greater than Steel. Formation of intermetallic compound of Al2Cu through the ARB process in Stainless Steel/Al/Cu composite is another finding of the present study.
1. Introduction Today, the process of metal-sheets shaping is considered as one of the important industrial operations on producing metals. Thus, a large scale of metal products in industrial countries is based on this process [1–5]. Of advantages of metal sheets are high elasticity module and proper consistency. Nonetheless, the huge market of metal products in industry always demands much more consistency. Today, multi-layer sheets of metal composite have increasingly been substituted for the common sheets. Multi-layer sheets of metal composite including alternative metal layers have been taken into account as to their ideal quality. The possibility of creating new properties through composing two or several kinds of metals in a multi-layer metal composite is the researchers' disposition to work in the ground of metal matrix composites. In order to produce multi-layer metal composite, various methods such as magnetic stir deposition, electrical deposition, and accumulative roll bonding (ARB) connection are utilized [5–10]. The process of ARB is one of the severe plastic deformation (SPD)
⁎
methods through which various kinds of ultrafine grinds (UFG) of metal-composite sheets can be manufactured. This process consists of several cycles of roll bonding, shearing, ordering, and connecting on solid state. In the process of ARB, a severe strain has been exerted to the metal sheet, whereas there is no change in the size of the piece [11]. The ARB process as to its simple equipment, accessibility, and the applicability of the process on the huge volume of pieces takes more advantages than the other methods of severe plastic deformation. In this method, at first, two sheets in equal size after superficial preparing are overlaid and rolled bond. After roll bonding their thickness come back to the initial. Then, the sheet will be divided into two parts, and this process will continue to several cycles. As the thickness is constant during the process, it can be continued until a high strain in order to have sheets of ultrafine grinds and high consistency. Fig. 1 illustrates a view of the process used in this study. Aluminum matrix composites (AMCs) because of possessing low density, high solidity, and low rate of erosion are considered as the favorite materials for aerospace and marine industry, nuclear energy,
Corresponding author at: Ton Duc Thang University, Ho Chi Minh City, Vietnam. E-mail addresses: [email protected] (H. Mansouri), [email protected] (M. Afrand).
https://doi.org/10.1016/j.jmapro.2019.08.025 Received 14 July 2019; Received in revised form 19 August 2019; Accepted 22 August 2019 Available online 26 September 2019 1526-6125/ © 2019 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.
Journal of Manufacturing Processes 46 (2019) 298–303
H. Mansouri, et al.
Fig. 1. A schematic process of accumulative roll bonding (ARB).
5 min; and then, in order to make a proper connection they were brushed by a solar brush and a drill in horizontal direction in a surface. After that, in order to prevent moving and slipping the sheets, they were fixed in steel wires from the edges. After the preparation and annealing of the samples (in 470 ℃ for 10 min), the process of ARB has been operated, and the thickness of 2.8 mm reached to 1.4 mm (decreased in 50 percent). After the first cycle of the roll bonding operation, the produced three-layer sheet were sheared into two parts in length. Then, the stages of preparation of the sample were used for subsequent cycles of roll bonding. The process of accumulative roll bonding was done on the samples up to the five cycles without lubricant, and without intermediate annealing among cycles. Microscopic images of cross-sections of composite samples were provided through optical and scanning electron microscope equipped with EDS. It has been done for evaluating the bonding conditions of the layers in different cycles of the ARB process as well as for investigating the inter-diffusion of the atoms of steel, Al and Cu. In the following, in order to investigate created phases of layer composite of Stainless Steel/ Al/Cu in various cycles of ARB, X-ray diffraction analysis tool has been utilized. The hardness test of micro-hardening of samples has been done. Micro-hardness of the samples was measured using M400-G1 micro-hardness tester with loads ranging from 10 to 50 g. Through selecting three points in steel layers, three in Al, and three in Cu removing maximum and minimum values, and averaging the hardness values, hardness of steel, Al, and Cu in different measurement cycles have been done, and related charts has been drawn.
and other structural applications [12,13]. Therefore, many researches have been done in this field, and various composites such as multi-layer metal composite of Al/Cu [14–18], Al/Pb [19], Al/Mg [11,20,21], Ni/ Cu/Al [22], and Mn/Cu/Al [23], through ARB have been produced and examined; and acceptable results have been obtained. The current study attempts to produce a new multi-layer metal composite in the form of a compounding Al sheets, Steel, and Cu utilizing ARB method. These types of composites are widely used in industry and household applications with the various advantages. A multi-layer metal composite of Stainless Steel/Al/Cu for its favorable mechanical and thermal properties, and also for anti-corrosion characteristic of stainless steel, and electrical and thermal conductivity of Al and Cu has unique properties. Investigating changes of ultrafine structure of composite samples produced through this method can be effectively used in system designing, and the required plastic deformation, as well as predicting favorable properties in multi-layer sheets of composites.
2. Materials and experiments In this study, 304 stainless steel sheets, AA1100 Al with a purity of 99%, and pure commercial Cu with a purity of 99.5% have been utilized. Chemical compound and dimensions of sheets utilized in the study are presented in Table 1. At first, in order to eliminating work hardening, and homogenization of the structure, the sheets of Steel, Al and Cu were annealed for an hour in temperatures of 850, 370 and 650 °C, respectively. In order to prevent oxidation of the surface of the samples, steel, Al, and Cu sheets were wrapped respectively in Cu, Al, and Cu foils in iron encasement including graphite powder under a complete anneal operation. After the operation, it chilled up to the inside temperature of the kiln. Before the ARB operation, the samples were prepared in superficial. Initially, in order to removing oxides, oils and surface pollutions, the foils were drowned in compound of 5% Nitric acid and 95% water for
3. Results and discussion Fig. 2 (A–E) illustrates microscopic images of cross-section of samples under the process of ARB after the cycles of 1, 2, 3, 4 and 5 related to total strains of 0.8, 1.6, 2.4, 3.2, and 4, respectively. According to these images, it is observed that during the accumulative roll bonding, proper connection are created among layers of Cu, Al, and Steel; and by
Table 1 Chemical compound and dimensions of sheets. Metal
Al (1100) Cu STS (304)
Element (%)
Dimension (mm)
Cu
Al
Fe
C
Mo
Co
Ni
Cr
0.03 > 99.5 0.20
Base Trace 0.005
0.6 < 0.005 Base
None None 0.06
None None 0.14
0.01 < 0.01 0.15
0.008 0.02 8.20
Trace Trace 18.6
299
1.5 × 40 × 150 0.5 × 40 × 150 0.8 × 40 × 150
Journal of Manufacturing Processes 46 (2019) 298–303
H. Mansouri, et al.
Fig. 2. Optical microscopic images of cross-section of the composite of Stainless Steel/Al/Cu produced after the cycles A) 1; B) 2; C) 3; D) 4; and E) 5 of ARB process.
increasing the number of cycles up to the five, a composite of Al matrix and distribution of the Cu and steel reinforcement has been formed. As is clear in Figs. 2C–E, cohesion of the Cu and steel layers has maintained only for the second cycle of composite production, but in the subsequent cycles, plastic instability occurred. In other words, after the second cycle of the process of roll bonding in Cu and Steel layers, necking, fracturing, and departing occurs (Figs. 2C–E); whereas, layers of Al maintain their cohesion. Plastic instability is created as to the different mechanical features of the available layers, first necking and then fracturing and departing occurs in the harder phase [24]. According to the fact that the hardness of the steel and Cu is greater than Al, so plastic stability first occurs in steel and then in Cu. As it is illustrated in Fig. 2, up to the second cycle of ARB process Cu and steel layers maintain their cohesion, and only a decrease of thickness (necking) occurs in some areas, but there is not any fractures in the layers. In fact, required strain for the fraction is greater than the strain for the necking [16,24]. By increasing the number of cycles up to the four, in addition to sever necking in Cu and steel layers, the phenomena of fraction and departing are seen. The striking point related to the ARB process on multi-layer composite is that in initial cycles, as to different mechanical properties of the layers, distribution of the Cu and steel layers is heterogeneous. But, with the increase of cycles of the ARB process, and accordingly, decrease of discrepancy of mechanical properties of the Steel, Cu, and Al layers, the distribution of Cu and steel within the Al matrix becomes more homogeneous. The existence of shear bonds in Al matrix especially in common boundary of Al/Cu and Al/Steel, and the movement of this shear bonds into Cu and Steel layers results shearing and
departing in hard layers of Cu and steel. The length of the Cu and Steel layers created in Al matrix depends on the distance of these shear bonds. It seems that in initial stages of producing composite (the first and the second cycle), the length of the steel and Cu layer is greater than the distance between shear bonds, so the incohesive layer of Cu and Steel in a long length is created in Al matrix. But, through increasing the number of the cycles, layers of Cu and Steel is cut by the shear bonds; and finally, a structure of Al matrix and re pieces of Cu and Steel with the smaller length of shear bonds are created. After conducting the first cycle of the process of ARB on steel, Cu, and Al in the second cycle, layers of Cu are overlaid, and in subsequent cycles, layers of steel are overlaid. As it is observed in Fig. 2. (C), as to the discrepancy of the atomic mass of steel, Al, and Cu common boundary of Steel, Al, and Cu in optical microscope can clearly be seen. Created connection in the last cycle (middle of the sample) in which the steel layer overlays on steel, cannot be recognized because of the severe viscosity. In order to examine the atoms of steel, Al, and Cu a scanning electron microscope equipped with linear elemental analysis has been utilized. Fig. 3 illustrates the curves of the diffusion of the atoms of steel, Al, and Cu after three and five cycles of ARB. According to the obtained results, during the ARB, atoms of Steel, Al, and Cu diffuse to one another. Diffusion area can be inflected by the atoms of Al in Cu and Steel layers, and also diffusion of Cu in steel layers and vice versa. In the subsequent cycles of ARB process, the existence of diffusion in common boundary of steel, Al, and Cu causes more homogenous connections. This phenomenon is known as inter-diffusion resulted from deformation. Inter-diffusion is resulted from three mechanism of atoms
300
Journal of Manufacturing Processes 46 (2019) 298–303
H. Mansouri, et al.
Fig. 3. SEM microstructure and linear elemental analysis in common boundaries of A) Al and Cu after three cycles ; B) Cu and Steel after three cycles; C) Al and Cu after five cycles of ARB process.
including phase or intermetallic compound which are created by the diffusion of Cu and Al together. It should be noted that through the increasing number of cycles up to the five, as to decrease of the thickness of the layers, and increase of common boundary between the layers, appropriate condition is provided for diffusing the atoms. Samples of composite of Stainless Steel/Al/Cu under the process of ARB were evaluated for investigation of intermetallic compounds.
displacement through mechanical work, diffusion through dislocation pipes, and diffusion through blank locations created from sever plastic deformation. Fig. 4 illustrates microscopic images of common boundary of composite layers after five cycles of ARB. As it is clear, in common boundary of the layers of Cu and Al, color-changed areas which are specified by arrows are seen. These areas are probably the areas of diffusion 301
Journal of Manufacturing Processes 46 (2019) 298–303
H. Mansouri, et al.
Fig. 4. A) Optical microscopic image; B) SEM image from cross-section of composite sample of Stainless Steel/Al/Cu after five cycles of ARB.
The color-changed layer shows the hardness number of 230 Vickers. As to this amount of hardness which is near to hardness scale of Al2Cu this area probably includes Al2Cu [25]. It should be noted that linear elemental analysis acknowledges the existence of this compound (Fig. 3). As it is obvious in Fig. 3 (C), through moving from the layer of Al to Cu there is intermetallic compound of Al2Cu with 33% of Cu. In addition to temperature and anneal duration, created strain in the sample through roll bonding has remarkable impact on microstructure, the size of the grind, and creation of the new phase. Severe strain or exerting numerous cycles of ARB on the composite causes creating ultrafine grinds on it. Following this, boundary of the grinds and dislocations also increase; therefore, it boosts diffusion in dissimilar metal layers boundary, and facilitates the constitution of intermetallic compounds. This phenomenon facilitates the creation of new phases in the sample [26]. Fig. 6 demonstrates changes of hardness of Stainless Steel, Al, and Cu layers in various cycles of ARB. It is observed that after producing composite of Stainless Steel, Al, and Cu remarkable increase occurs in hardness of Steel, Al, and Cu layers; and through progressing ARB, the rate of hardness has been decreased in Cu and Al. Severe increase in relatively low level of strain has been attributed to work hardening;
Fig. 5. X-ray diffraction pattern of composite samples of Stainless Steel/Al/Cu produced by various cycles of ARB.
Fig. 5 demonstrates x-ray diffraction patterns related to the cycles one to five of ARB. As it is clear, in x-ray diffraction patterns of cycle five of ARB, in addition to elemental peaks of steel, Al, and Cu the peaks related to intermetallic compound of Al2Cu has been created as well. Therefore, as to the area inflected by diffusion in common boundary of Al/Cu layers, and also existence of peaks related to elemental Al and Cu in x-ray diffraction pattern, it is expected that intermetallic compounds have been created in common boundary of Al and Cu layers. In order for rigorous investigation of diffusion area in common boundary of these two layers, micro-hardness of color-changed area (specified area in Fig. 4) in the sample of five cycles under ARB has been measured.
Fig. 6. Changes of hardness of Stainless Steel, Al, and Cu layers in various cycles of ARB process. 302
Journal of Manufacturing Processes 46 (2019) 298–303
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and, as a result, to constituting more boundary of incidental grinds/cell walls resulted from ultrafine grinding [27]. As it mentioned earlier, from cycle one to five, the amount of micro-hardness in two layers of Al and Cu increases in a lower rate than before the cycle one, which is probably related to the effect of work hardening and saturation of density of dislocations. According to research, it has been indicated that discrepancy in thermal expansion coefficient of layers, the rate of work hardening (discrepancy in stacking fault fnergy), and fine grinding has an impact on changes of micro-hardness of the layers during various cycles of ARB process [24].
of sheet metals. J Manuf Process 2017;27:169–78. [6] Arigela VG, Palukuri NR, Singh D, Kolli SK, Jayaganthan R, Chekhonin P, et al. Evolution of microstructure and mechanical properties in 2014 and 6063 similar and dissimilar aluminium alloy laminates produced by accumulative roll bonding. J Alloys Compd 2019;790:917–27. [7] Wang Y, Wu H, Liu X, Jiao Y, Sun J, Wu R, et al. High-strength and ductility bimodal-grained Al–Li/Al–Li–Zr composite produced by accumulative roll bonding. Mater Sci Eng A 2019;761:138049. [8] Ahmadi E, Ranjkesh M, Mansoori E, Fattahi M, Mojallal RY, Amirkhanlou S. Microstructure and mechanical properties of Al/ZrC/TiC hybrid nanocomposite filler metals of tungsten inert gas welding fabricated by accumulative roll bonding. J Manuf Process 2017;26:173–7. [9] Morovvati MR, Dariani BM. The effect of annealing on the formability of aluminum 1200 after accumulative roll bonding. J Manuf Process 2017;30:241–54. [10] Tamimi S, Gracio JJ, Lopes AB, Ahzi S, Barlat F. Asymmetric rolling of interstitial free steel sheets: microstructural evolution and mechanical properties. J Manuf Process 2018;31:583–92. [11] Chang H, Zheng M, Xu C, Fan G, Brokmeier H, Wu K. Microstructure and mechanical properties of the Mg/Al multilayer fabricated by accumulative roll bonding (ARB) at ambient temperature. Mater Sci Eng A 2012;543:249–56. [12] Chawla N, Deng X, Schnell D. Thermal expansion anisotropy in extruded SiC particle reinforced 2080 aluminum alloy matrix composites. Mater Sci Eng A 2006;426(1):314–22. [13] Tjong SC, Ma Z. Microstructural and mechanical characteristics of in situ metal matrix composites. Mater Sci Eng R Rep 2000;29(3):49–113. [14] Mehr VY, Toroghinejad MR, Rezaeian A. Mechanical properties and microstructure evolutions of multilayered Al–Cu composites produced by accumulative roll bonding process and subsequent annealing. Mater Sci Eng A 2014;601:40–7. [15] Alizadeh M, Talebian M. Fabrication of Al/Cu p composite by accumulative roll bonding process and investigation of mechanical properties. Mater Sci Eng A 2012;558:331–7. [16] Eizadjou M, Talachi AK, Manesh HD, Shahabi HS, Janghorban K. Investigation of structure and mechanical properties of multi-layered Al/Cu composite produced by accumulative roll bonding (ARB) process. Compos Sci Technol 2008;68(9):2003–9. [17] Hsieh C-C, Shi M-S, Wu W. Growth of intermetallic phases in Al/Cu composites at various annealing temperatures during the ARB process. Met Mater Int 2012;18(1):1–6. [18] Toroghinejad MR, Jamaati R, Dutkiewicz J, Szpunar JA. Investigation of nanostructured aluminum/copper composite produced by accumulative roll bonding and folding process. Mater Des 2013;51:274–9. [19] Dehsorkhi RN, Qods F, Tajally M. Investigation on microstructure and mechanical properties of Al–Zn composite during accumulative roll bonding (ARB) process. Mater Sci Eng A 2011;530:63–72. [20] Chen M, Hsieh H, Wu W. The evolution of microstructures and mechanical properties during accumulative roll bonding of Al/Mg composite. J Alloys Compd 2006;416(1):169–72. [21] Wu K, Chang H, Maawad E, Gan W, Brokmeier H, Zheng M. Microstructure and mechanical properties of the Mg/Al laminated composite fabricated by accumulative roll bonding (ARB). Mater Sci Eng A 2010;527(13):3073–8. [22] Shabani A, Toroghinejad MR, Shafyei A. Fabrication of Al/Ni/Cu composite by accumulative roll bonding and electroplating processes and investigation of its microstructure and mechanical properties. Mater Sci Eng A 2012;558:386–93. [23] Alizadeh M, Samiei M. Fabrication of nanostructured Al/Cu/Mn metallic multilayer composites by accumulative roll bonding process and investigation of their mechanical properties. Mater Des 2014;56:680–4. [24] Mehr VY, Rezaeian A, Toroghinejad MR. Application of accumulative roll bonding and anodizing process to produce Al–Cu–Al 2 O 3 composite. Mater Des 2015;70:53–9. [25] Zhang Y, Yamane T, Hirao K, Minamino Y. Microstructures and Vickers hardness of rapidly solidified Al-Cu alloys near the Al-Al2Cu equilibrium eutectic composition. J Mater Sci 1991;26(21):5799–805. [26] Zhang R, Acoff VL. Processing sheet materials by accumulative roll bonding and reaction annealing from Ti/Al/Nb elemental foils. Mater Sci Eng A 2007;463(1):67–73. [27] Park K-T, Kwon H-J, Kim W-J, Kim Y-S. Microstructural characteristics and thermal stability of ultrafine grained 6061 Al alloy fabricated by accumulative roll bonding process. Mater Sci Eng A 2001;316(1):145–52.
4. Conclusion In the present study, the process of ARB on the bonds of stainless steel 304, Al, and Cu has been done in order to produce composite of Stainless Steel/Al/Cu in preheating temperature of 470 0 C without lubricant, up to the five cycles (the strain equals to four). Major findings of the study cover the following points: 1- Producing ultrafine grinds of Stainless Steel/Al/Cu with the distribution of Cu and steel in Al is possible after the fifth cycle of ARB process. 2- Simultaneous roll bonding of layer composite of stainless steel causes necking, fracturing, and departing of hard phase of steel and Cu on the fine matrix of Al after five cycles of ARB process. 3- Microscopic images showed that progressing of the process on common boundary of composite layers creates a proper connection. 4- Deformation of sever plastic of Stainless Steel/Al/Cu composite during the ARB process causes inter-diffusion of steel, Al, and Cu to one another. The rate of diffusion of Cu on Al is greater, and it boosts through increasing the number of cycles of the process and the degree of deformation. 5- By increasing the number of cycles of the process, and in fact, by increasing the amount of supersaturation, the energy resulted from hotworking and the diffusion resulted from grind boundary on composite samples under ARB, intermetallic compound of Al2Cu has been constituted. Declaration of Competing Interest None References [1] Iriondo E, Alcaraz JL, Daehn GS, Gutiérrez MA, Jimbert P. Shape calibration of high strength metal sheets by electromagnetic forming. J Manuf Process 2013;15:183–93. [2] Liu H, Zhang W, Gau J-T, Shen Z, Zhang G, Ma Y, et al. Microscale laser flexible dynamic forming of Cu/Ni laminated composite metal sheets. J Manuf Process 2018;35:51–60. [3] Paul SK. Path independent limiting criteria in sheet metal forming. J Manuf Process 2015;20:291–303. [4] Singh J, Singh Arora K, Shajan N, Shukla DK, Shome M. Role of bead shape and dispersed intermetallic phases in determining the strength of CMT brazed DP780 lap joints. J Manuf Process 2019;44:207–15. [5] Zhang Y, Dhaigude M, Wang J. The anvil effect in the spherical indentation testing
303
Contents lists available at ScienceDirect
Journal of Manufacturing Processes journal homepage: www.elsevier.com/locate/manpro
Producing multi-layer composite of stainless steel/aluminum/copper by accumulative roll bonding (ARB) process ⁎
Hamidreza Mansouria, , Beitallah Eghbalia, Masoud Afrandb,c,
T
⁎
a
Materials Engineering Faculty, Sahand University of Technology, Tabriz, Iran Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam c Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam b
A R T I C LE I N FO
A B S T R A C T
Keywords: Severe plastic deformation Accumulative roll bonding (ARB) Multi-layered composite Intermetallic compound
Mechanical process of Accumulative Roll Bonding (ARB) is one of the severe plastic deformation methods which can be contributed to produce ultrafine grind composites. In this research, multi-layered composite of stainless steel/aluminum/copper after five cycles of accumulative roll bonding has been produced. In order to examine the microstructure of the sample during the process of ARB, images of optical microscope (OM), and scanning electron microscope (SEM) of sample cross section were provided. Moreover, inter-diffusion of atoms of Steel, Al, and Cu has been examined through linear elemental analysis. In order for recognition of created phases in composite, X-Ray diffraction analysis (XRD) has been done. At the end, a test of hardness has been done on various layers of composite. The results showed that in the first and second cycle of the ARB, it has not been created any plastic instability in the layers. By increasing the number of the cycle of accumulative roll bonding up to the five, plastic instability (necking and fracturing) will be observed. According to the result of this study, during the process of ARB, proper connection has been created among the layers. By increasing the cycles up to the five, a composite of aluminum matrix, grinds reinforcing Cu, and steel will be produced. In addition, the investigation of atomic diffusion indicates that the diffusion of the atoms of Cu and Al is greater than Steel. Formation of intermetallic compound of Al2Cu through the ARB process in Stainless Steel/Al/Cu composite is another finding of the present study.
1. Introduction Today, the process of metal-sheets shaping is considered as one of the important industrial operations on producing metals. Thus, a large scale of metal products in industrial countries is based on this process [1–5]. Of advantages of metal sheets are high elasticity module and proper consistency. Nonetheless, the huge market of metal products in industry always demands much more consistency. Today, multi-layer sheets of metal composite have increasingly been substituted for the common sheets. Multi-layer sheets of metal composite including alternative metal layers have been taken into account as to their ideal quality. The possibility of creating new properties through composing two or several kinds of metals in a multi-layer metal composite is the researchers' disposition to work in the ground of metal matrix composites. In order to produce multi-layer metal composite, various methods such as magnetic stir deposition, electrical deposition, and accumulative roll bonding (ARB) connection are utilized [5–10]. The process of ARB is one of the severe plastic deformation (SPD)
⁎
methods through which various kinds of ultrafine grinds (UFG) of metal-composite sheets can be manufactured. This process consists of several cycles of roll bonding, shearing, ordering, and connecting on solid state. In the process of ARB, a severe strain has been exerted to the metal sheet, whereas there is no change in the size of the piece [11]. The ARB process as to its simple equipment, accessibility, and the applicability of the process on the huge volume of pieces takes more advantages than the other methods of severe plastic deformation. In this method, at first, two sheets in equal size after superficial preparing are overlaid and rolled bond. After roll bonding their thickness come back to the initial. Then, the sheet will be divided into two parts, and this process will continue to several cycles. As the thickness is constant during the process, it can be continued until a high strain in order to have sheets of ultrafine grinds and high consistency. Fig. 1 illustrates a view of the process used in this study. Aluminum matrix composites (AMCs) because of possessing low density, high solidity, and low rate of erosion are considered as the favorite materials for aerospace and marine industry, nuclear energy,
Corresponding author at: Ton Duc Thang University, Ho Chi Minh City, Vietnam. E-mail addresses: [email protected] (H. Mansouri), [email protected] (M. Afrand).
https://doi.org/10.1016/j.jmapro.2019.08.025 Received 14 July 2019; Received in revised form 19 August 2019; Accepted 22 August 2019 Available online 26 September 2019 1526-6125/ © 2019 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.
Journal of Manufacturing Processes 46 (2019) 298–303
H. Mansouri, et al.
Fig. 1. A schematic process of accumulative roll bonding (ARB).
5 min; and then, in order to make a proper connection they were brushed by a solar brush and a drill in horizontal direction in a surface. After that, in order to prevent moving and slipping the sheets, they were fixed in steel wires from the edges. After the preparation and annealing of the samples (in 470 ℃ for 10 min), the process of ARB has been operated, and the thickness of 2.8 mm reached to 1.4 mm (decreased in 50 percent). After the first cycle of the roll bonding operation, the produced three-layer sheet were sheared into two parts in length. Then, the stages of preparation of the sample were used for subsequent cycles of roll bonding. The process of accumulative roll bonding was done on the samples up to the five cycles without lubricant, and without intermediate annealing among cycles. Microscopic images of cross-sections of composite samples were provided through optical and scanning electron microscope equipped with EDS. It has been done for evaluating the bonding conditions of the layers in different cycles of the ARB process as well as for investigating the inter-diffusion of the atoms of steel, Al and Cu. In the following, in order to investigate created phases of layer composite of Stainless Steel/ Al/Cu in various cycles of ARB, X-ray diffraction analysis tool has been utilized. The hardness test of micro-hardening of samples has been done. Micro-hardness of the samples was measured using M400-G1 micro-hardness tester with loads ranging from 10 to 50 g. Through selecting three points in steel layers, three in Al, and three in Cu removing maximum and minimum values, and averaging the hardness values, hardness of steel, Al, and Cu in different measurement cycles have been done, and related charts has been drawn.
and other structural applications [12,13]. Therefore, many researches have been done in this field, and various composites such as multi-layer metal composite of Al/Cu [14–18], Al/Pb [19], Al/Mg [11,20,21], Ni/ Cu/Al [22], and Mn/Cu/Al [23], through ARB have been produced and examined; and acceptable results have been obtained. The current study attempts to produce a new multi-layer metal composite in the form of a compounding Al sheets, Steel, and Cu utilizing ARB method. These types of composites are widely used in industry and household applications with the various advantages. A multi-layer metal composite of Stainless Steel/Al/Cu for its favorable mechanical and thermal properties, and also for anti-corrosion characteristic of stainless steel, and electrical and thermal conductivity of Al and Cu has unique properties. Investigating changes of ultrafine structure of composite samples produced through this method can be effectively used in system designing, and the required plastic deformation, as well as predicting favorable properties in multi-layer sheets of composites.
2. Materials and experiments In this study, 304 stainless steel sheets, AA1100 Al with a purity of 99%, and pure commercial Cu with a purity of 99.5% have been utilized. Chemical compound and dimensions of sheets utilized in the study are presented in Table 1. At first, in order to eliminating work hardening, and homogenization of the structure, the sheets of Steel, Al and Cu were annealed for an hour in temperatures of 850, 370 and 650 °C, respectively. In order to prevent oxidation of the surface of the samples, steel, Al, and Cu sheets were wrapped respectively in Cu, Al, and Cu foils in iron encasement including graphite powder under a complete anneal operation. After the operation, it chilled up to the inside temperature of the kiln. Before the ARB operation, the samples were prepared in superficial. Initially, in order to removing oxides, oils and surface pollutions, the foils were drowned in compound of 5% Nitric acid and 95% water for
3. Results and discussion Fig. 2 (A–E) illustrates microscopic images of cross-section of samples under the process of ARB after the cycles of 1, 2, 3, 4 and 5 related to total strains of 0.8, 1.6, 2.4, 3.2, and 4, respectively. According to these images, it is observed that during the accumulative roll bonding, proper connection are created among layers of Cu, Al, and Steel; and by
Table 1 Chemical compound and dimensions of sheets. Metal
Al (1100) Cu STS (304)
Element (%)
Dimension (mm)
Cu
Al
Fe
C
Mo
Co
Ni
Cr
0.03 > 99.5 0.20
Base Trace 0.005
0.6 < 0.005 Base
None None 0.06
None None 0.14
0.01 < 0.01 0.15
0.008 0.02 8.20
Trace Trace 18.6
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1.5 × 40 × 150 0.5 × 40 × 150 0.8 × 40 × 150
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Fig. 2. Optical microscopic images of cross-section of the composite of Stainless Steel/Al/Cu produced after the cycles A) 1; B) 2; C) 3; D) 4; and E) 5 of ARB process.
increasing the number of cycles up to the five, a composite of Al matrix and distribution of the Cu and steel reinforcement has been formed. As is clear in Figs. 2C–E, cohesion of the Cu and steel layers has maintained only for the second cycle of composite production, but in the subsequent cycles, plastic instability occurred. In other words, after the second cycle of the process of roll bonding in Cu and Steel layers, necking, fracturing, and departing occurs (Figs. 2C–E); whereas, layers of Al maintain their cohesion. Plastic instability is created as to the different mechanical features of the available layers, first necking and then fracturing and departing occurs in the harder phase [24]. According to the fact that the hardness of the steel and Cu is greater than Al, so plastic stability first occurs in steel and then in Cu. As it is illustrated in Fig. 2, up to the second cycle of ARB process Cu and steel layers maintain their cohesion, and only a decrease of thickness (necking) occurs in some areas, but there is not any fractures in the layers. In fact, required strain for the fraction is greater than the strain for the necking [16,24]. By increasing the number of cycles up to the four, in addition to sever necking in Cu and steel layers, the phenomena of fraction and departing are seen. The striking point related to the ARB process on multi-layer composite is that in initial cycles, as to different mechanical properties of the layers, distribution of the Cu and steel layers is heterogeneous. But, with the increase of cycles of the ARB process, and accordingly, decrease of discrepancy of mechanical properties of the Steel, Cu, and Al layers, the distribution of Cu and steel within the Al matrix becomes more homogeneous. The existence of shear bonds in Al matrix especially in common boundary of Al/Cu and Al/Steel, and the movement of this shear bonds into Cu and Steel layers results shearing and
departing in hard layers of Cu and steel. The length of the Cu and Steel layers created in Al matrix depends on the distance of these shear bonds. It seems that in initial stages of producing composite (the first and the second cycle), the length of the steel and Cu layer is greater than the distance between shear bonds, so the incohesive layer of Cu and Steel in a long length is created in Al matrix. But, through increasing the number of the cycles, layers of Cu and Steel is cut by the shear bonds; and finally, a structure of Al matrix and re pieces of Cu and Steel with the smaller length of shear bonds are created. After conducting the first cycle of the process of ARB on steel, Cu, and Al in the second cycle, layers of Cu are overlaid, and in subsequent cycles, layers of steel are overlaid. As it is observed in Fig. 2. (C), as to the discrepancy of the atomic mass of steel, Al, and Cu common boundary of Steel, Al, and Cu in optical microscope can clearly be seen. Created connection in the last cycle (middle of the sample) in which the steel layer overlays on steel, cannot be recognized because of the severe viscosity. In order to examine the atoms of steel, Al, and Cu a scanning electron microscope equipped with linear elemental analysis has been utilized. Fig. 3 illustrates the curves of the diffusion of the atoms of steel, Al, and Cu after three and five cycles of ARB. According to the obtained results, during the ARB, atoms of Steel, Al, and Cu diffuse to one another. Diffusion area can be inflected by the atoms of Al in Cu and Steel layers, and also diffusion of Cu in steel layers and vice versa. In the subsequent cycles of ARB process, the existence of diffusion in common boundary of steel, Al, and Cu causes more homogenous connections. This phenomenon is known as inter-diffusion resulted from deformation. Inter-diffusion is resulted from three mechanism of atoms
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Fig. 3. SEM microstructure and linear elemental analysis in common boundaries of A) Al and Cu after three cycles ; B) Cu and Steel after three cycles; C) Al and Cu after five cycles of ARB process.
including phase or intermetallic compound which are created by the diffusion of Cu and Al together. It should be noted that through the increasing number of cycles up to the five, as to decrease of the thickness of the layers, and increase of common boundary between the layers, appropriate condition is provided for diffusing the atoms. Samples of composite of Stainless Steel/Al/Cu under the process of ARB were evaluated for investigation of intermetallic compounds.
displacement through mechanical work, diffusion through dislocation pipes, and diffusion through blank locations created from sever plastic deformation. Fig. 4 illustrates microscopic images of common boundary of composite layers after five cycles of ARB. As it is clear, in common boundary of the layers of Cu and Al, color-changed areas which are specified by arrows are seen. These areas are probably the areas of diffusion 301
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Fig. 4. A) Optical microscopic image; B) SEM image from cross-section of composite sample of Stainless Steel/Al/Cu after five cycles of ARB.
The color-changed layer shows the hardness number of 230 Vickers. As to this amount of hardness which is near to hardness scale of Al2Cu this area probably includes Al2Cu [25]. It should be noted that linear elemental analysis acknowledges the existence of this compound (Fig. 3). As it is obvious in Fig. 3 (C), through moving from the layer of Al to Cu there is intermetallic compound of Al2Cu with 33% of Cu. In addition to temperature and anneal duration, created strain in the sample through roll bonding has remarkable impact on microstructure, the size of the grind, and creation of the new phase. Severe strain or exerting numerous cycles of ARB on the composite causes creating ultrafine grinds on it. Following this, boundary of the grinds and dislocations also increase; therefore, it boosts diffusion in dissimilar metal layers boundary, and facilitates the constitution of intermetallic compounds. This phenomenon facilitates the creation of new phases in the sample [26]. Fig. 6 demonstrates changes of hardness of Stainless Steel, Al, and Cu layers in various cycles of ARB. It is observed that after producing composite of Stainless Steel, Al, and Cu remarkable increase occurs in hardness of Steel, Al, and Cu layers; and through progressing ARB, the rate of hardness has been decreased in Cu and Al. Severe increase in relatively low level of strain has been attributed to work hardening;
Fig. 5. X-ray diffraction pattern of composite samples of Stainless Steel/Al/Cu produced by various cycles of ARB.
Fig. 5 demonstrates x-ray diffraction patterns related to the cycles one to five of ARB. As it is clear, in x-ray diffraction patterns of cycle five of ARB, in addition to elemental peaks of steel, Al, and Cu the peaks related to intermetallic compound of Al2Cu has been created as well. Therefore, as to the area inflected by diffusion in common boundary of Al/Cu layers, and also existence of peaks related to elemental Al and Cu in x-ray diffraction pattern, it is expected that intermetallic compounds have been created in common boundary of Al and Cu layers. In order for rigorous investigation of diffusion area in common boundary of these two layers, micro-hardness of color-changed area (specified area in Fig. 4) in the sample of five cycles under ARB has been measured.
Fig. 6. Changes of hardness of Stainless Steel, Al, and Cu layers in various cycles of ARB process. 302
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and, as a result, to constituting more boundary of incidental grinds/cell walls resulted from ultrafine grinding [27]. As it mentioned earlier, from cycle one to five, the amount of micro-hardness in two layers of Al and Cu increases in a lower rate than before the cycle one, which is probably related to the effect of work hardening and saturation of density of dislocations. According to research, it has been indicated that discrepancy in thermal expansion coefficient of layers, the rate of work hardening (discrepancy in stacking fault fnergy), and fine grinding has an impact on changes of micro-hardness of the layers during various cycles of ARB process [24].
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4. Conclusion In the present study, the process of ARB on the bonds of stainless steel 304, Al, and Cu has been done in order to produce composite of Stainless Steel/Al/Cu in preheating temperature of 470 0 C without lubricant, up to the five cycles (the strain equals to four). Major findings of the study cover the following points: 1- Producing ultrafine grinds of Stainless Steel/Al/Cu with the distribution of Cu and steel in Al is possible after the fifth cycle of ARB process. 2- Simultaneous roll bonding of layer composite of stainless steel causes necking, fracturing, and departing of hard phase of steel and Cu on the fine matrix of Al after five cycles of ARB process. 3- Microscopic images showed that progressing of the process on common boundary of composite layers creates a proper connection. 4- Deformation of sever plastic of Stainless Steel/Al/Cu composite during the ARB process causes inter-diffusion of steel, Al, and Cu to one another. The rate of diffusion of Cu on Al is greater, and it boosts through increasing the number of cycles of the process and the degree of deformation. 5- By increasing the number of cycles of the process, and in fact, by increasing the amount of supersaturation, the energy resulted from hotworking and the diffusion resulted from grind boundary on composite samples under ARB, intermetallic compound of Al2Cu has been constituted. Declaration of Competing Interest None References [1] Iriondo E, Alcaraz JL, Daehn GS, Gutiérrez MA, Jimbert P. Shape calibration of high strength metal sheets by electromagnetic forming. J Manuf Process 2013;15:183–93. [2] Liu H, Zhang W, Gau J-T, Shen Z, Zhang G, Ma Y, et al. Microscale laser flexible dynamic forming of Cu/Ni laminated composite metal sheets. J Manuf Process 2018;35:51–60. [3] Paul SK. Path independent limiting criteria in sheet metal forming. J Manuf Process 2015;20:291–303. [4] Singh J, Singh Arora K, Shajan N, Shukla DK, Shome M. Role of bead shape and dispersed intermetallic phases in determining the strength of CMT brazed DP780 lap joints. J Manuf Process 2019;44:207–15. [5] Zhang Y, Dhaigude M, Wang J. The anvil effect in the spherical indentation testing
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