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Effect of Cu interlayer on joining 93W and Mo1 alloys by plasma activated sintering
Accepted Manuscript Effect of Cu interlayer on joining 93W and Mo1 alloys by plasma activated sintering Mei Rao, Liangmeng Zhang, Jiang Zhang, Guoqiang Luo, Qiang Shen PII: DOI: Reference:
S0167-577X(17)30693-6 http://dx.doi.org/10.1016/j.matlet.2017.04.132 MLBLUE 22553
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
1 April 2017 28 April 2017 28 April 2017
Please cite this article as: M. Rao, L. Zhang, J. Zhang, G. Luo, Q. Shen, Effect of Cu interlayer on joining 93W and Mo1 alloys by plasma activated sintering, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet. 2017.04.132
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.
Effect of Cu interlayer on joining 93W and Mo1 alloys by plasma activated sintering Mei Rao, Liangmeng Zhang, Jiang Zhang*, Guoqiang Luo, Qiang Shen State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, P. R. China * Corresponding author: Tel.: 027-87168806; E-mail: [email protected] Abstract: 93W and Mo1 were bonded with and without Cu interlayer by plasma activated sintering. The bonding temperature was decreased greatly with Cu interlayer. Shear strength of 93W/Cu foil/Mo1 and 93W/Cu film/Mo1 were 148.4 MPa and 193.3 MPa, respectively. Elements were fully diffused at 93W/Cu and Cu/Mo1 interfaces. Fe-Ni binder in 93W alloy has a sound diffusion with Cu interlayer, and Ni enriched in diffusion interface and formed Cu-Ni alloy at the interface of the 93W/Cu film/Mo1 joint, which led to the increasing in bonding strength of joints greatly. Keywords: Cu interlayer, diffusion, plasma activated sintering, microstructure 1. Introduction 93W and Mo1 alloys process an attractive combination of mechanical properties including high temperature strength, high thermal conductivity, low thermal expansion, and excellent performance in neutron flux environments[1,2]. Both 93W and Mo1 are potential candidates for use in aerospace, automotive, military and nuclear technologies[3,4]. Therefore, it is essential to make a investigation on joining 93W and Mo1. However, due to differences in melting point, thermal conductivity of 93W and Mo1 alloys, it is difficult to obtain a good-quality joint[5]. Adding interlayer is an approach to decrease bonding temperature and increase bonding strength. It is reported that W can be bonded to Mo by adding Pa foil and Ni-Mo alloy[5,6]. Copper is ductile metal which has adequate physical contact with base metal. Jian Zhang[7] has reported that shear strength of Cu/Mo joints is 79 MPa. Chuangbin
1
Wang[8] has employed diffusion welding method to join 93W to OFC and firmly welded joint without large distortion or damage is obtained. Plasma activated sintering (PAS) has become widespread in use and attracted considerable attention recently[9,10]. Recently, PAS has been employed as a joining method to weld dissimilar metals. Yajie guo[11] has used plasma activated sintering process to fabricate multilayered Cu/Al composites successfully. PAS is also used in bonding Mg and Al, shortened the bonding time as a result the formation of brittle Mg-Al intermetallics is prevented[12]. In the present 93W alloy and Mo1 alloy were bonded with and without Cu interlayer by using plasma activated sintering process. There were two approaches to adding Cu interlayer, one was to use a 25 µm Cu foil, the other was to deposit Cu films on 93W and Mo1 by using megnetron sputtering. Microstructure and mechnical properities of bonded joints were investigated. 2. Experimental procedure For the experiment, 93W alloy (93 wt% tungsten with nickel and iron as the additives) and Mo1 alloy (Mo ≥ 99.9 wt%) were sliced into planchets of which the dimension were Φ25 mm × 8mm. The Cu foil (Cu ≥ 99.99 wt%) were cut into 25 mm in diameter. Before bonding process, base metals were first burnished in proper sequence with various grades of SiC grit paper, and then cleaned ultrasonically in acetone. Cu films (Cu ≥ 99.99 wt%) about 500 nm in thickness were deposited on 93W and Mo1 surfaces by magnetron sputtering. PAS apparatus (Ed-Pas) was applied to join 93W and Mo1 slices with Cu interlayer which were assembled into a sandwich structure. A compressive load of 9.8 kN, corresponding to a pressure of 20 MPa, was applied before heating. The vacuum pressure was less than 10 Pa. The sylindrical samples were heated to the bonding temperature, holding for 900 s and finally free cooling.
2
To access mechanical properties of joints, MTS - 810 universal machine was utilized to test shear strength of joints at a loading speed of 0.5 mm/s at room temperature. The bonded joints were observed via a field emission scanning electron microscope (FESEM, FEI Quanta 250FEG). And elements distribution at the interface were analyzed with an electron probe micro-analyzer ( EPMA, JXA - 8100) and an X-ray diffraction system (XRD, Rigaku Ultima III). 3. Results and discussion 3.1 Mechanical characterization Table 1 illustrates shear strength of 93W/Mo1 joints with and without Cu interlayer. Without Cu interlayer, the shear strength of 93W/Mo1 joints is 25.4 MPa. Adding Cu foil as an interlayer, the average shear strength of 93W/Cu foil/Mo1 joint fabricated at 850°C reaches 148.4 MPa. By using Cu film interlayer, bonding temperature decreases to 700°C, the average shear strength is 193.3 MPa, nearly twice more than that of Ni-Mo alloy interlayer (ref.[6]). Therefore, by adding Cu interlayer, 93W and Mo1 can not only be bonded at low temperature but also exhibit a substantial improvement in bonding strength. Table 1 Shear strength of 93W/Mo1 joints with and without Cu interlayer
Specimen
Shear
Bonding parameters
strength
Temperature (°C)
Holding time (s)
Pressure (MPa)
93W/Mo1
1000
900
20
23.4±5
93W/Cu foil/Mo1
850
900
20
148.4±10
93W/Cu film/Mo1
700
900
20
193.3±12
(MPa)
3.2. Microstructure characterization Fig. 1(a) and (b) illustrates microstructure of the 93W/Mo1 joint fabricated at 1000 °C. It is obvious that micro-cracks appear at the 93W/Mo1 boundary, indicating that atomic diffusion at the interface is insufficient and it is difficult to join 93W and Mo1 alloy below 1000°C. Fig. 1(c) and (d) shows
3
microstructure and elemental distribution of the 93W/Cu foil/Mo1 bonded joint. In Fig. 1 (c), the 93W/Cu foil and Cu foil/Mo1 interfaces are free of voids, reaction layers or defects. The diffusion coefficient usually reads D=Do exp(-Q/RT), where Do is the diffusion prefactor and Q is the diffusion activation energy [13]. The diffusion activation energy Q Ni-Cu is 41.2 KJ/mol [14], QFe-Cu is 187 KJ/mol [13], while QW-Cu is 257 KJ/mol [15] which is much higher than than of QNi-Cu and QFe-Cu. So from Fig. 1(d), it also can be found that Cu atoms are inclined to diffuse into the Fe-Ni binder.
Fig. 1 (a) Microstructure of 93W/Mo1 joint; (b) Enlarged BSE image of 93W/Mo1 joint; (c) SEM image of the 93W/Cu foil/Mo1 interface; (d) The elemental area distributions of 93W/Cu foil/Mo1 bonded joint. Fig. 2 (a) shows the surface morphologies of the Cu film. Cu grains are strip shaped and of high crystallization. The thickness of Cu film is uniform and about 500 nm (Fig. 2 (b) ), and the diffusion layer between Mo1 base metal and the Cu film is more than 0.5 µm, which means that the mutual diffusion between the Cu film and Mo1 base metal is competent before bonding process. It can be inferred that the deposition of Cu film is a pre-diffusion process between Cu and base metal, as a consequence, the bonding temperature can be decreased greatly.
4
No voids or cracks appear at the 93W/Cu film/Mo1interfaces in Fig. 2 (c), suggesting that the 93W/Mo1 joint with Cu film interlayer is of high quality. There are five regions (marked I, II, III, IV, V) at the 93W/Cu film/Mo1 interface, as it is shown in Fig. 2 (d). Region I and V are the base metal of W and Mo1. The continuous gradient distributions regions II and IV are W-riched and Mo-riched solid solution layers, and region III is a Cu-riched layer. It can be discovered that Cu mostly distributes in the diffusion interface, and Cu has a concentration at the Fe-Ni binder. At diffusion interface the atomic composition is 88.93% Cu, 7.22% Ni and a few Fe, W and Mo, indicating that the possible phase at the Cu-riched area is Cu-Ni alloy dissolved with Fe, Mo and W atoms. According to ref[16], Cu-Ni alloy possess higher stacking fault energies than pure Cu. As a result the ultimate tensile strength of Cu-Ni alloy increases. In the 93W/Cu film/Mo1 joint, Cu-Ni alloy, nearly 8 at% of Ni, formed at diffusion interface, which contributes to the increasing of bonding strength.
Fig. 2 Surface morphologies of Cu film: (a) Cu film on base metals, (b) Cross-section morphology and elemental distributions on Mo1 side; (c) SEM image of the interface of 93W/Cu film/Mo1 joint; (d) Elemental distributions across the bonded joint. Table 2 Elemental compositions of the selected points 1-6 (Marked in Fig.4)
5
Element Composition (at%) Points
W
Mo
Cu
Fe
Ni
Possible Phases
1
100
-
-
-
-
W
2
8.98
-
8.15
30.97
51.90
Fe-Ni(ss, Cu, W)
3
5.90
0.64
85.42
1.55
6.49
Cu-Ni(ss, Fe, W, Mo)
4
0.98
1.02
88.93
1.84
7.22
Cu-Ni(ss, Fe, Mo, W)
5
0.68
67.81
23.82
3.49
4.20
Mo(ss, Cu, Ni, Fe)
6
-
100
-
-
-
Mo
3.3 Fracture analysis Fig.3 displays the XRD pattern of fracture surfaces of 93W/Mo1 joints with Cu interlayer. From Fig.3 (a) and (b), the phase on 93W sides is primarily Cu, and phase on Mo1 sides is mainly Mo, meanwhile very weak peaks of Cu are detected on the fracture surface of Mo1 side. It can be inferred that fracture of 93W/Cu foil/Mo1 joint is mainly occurred at Cu foil/Mo1 interface. For 93W/Cu film/Mo1 joint, the phases on the 93W side are W and Cu (Fig.3(c)), and the phases on the Mo1 side are Mo and Cu (Fig.3(d)). Compared to pure Cu peaks, Cu peaks on the 93W side have a slight deviation, suggesting that the diffusion at the 93W/Cu film/Mo1 interface is adequate and Cu has formed solid solution and enhanced the bonding of 93W and Mo1 alloys. And it can be concluded that the fracture of the 93W/Cu film/Mo1 joint mostly occurs at the Cu solid solution layer.
Fig.3 XRD pattern of fracture surfaces of 93W/Mo1 joints with Cu interlayer: (a) 93W side and (b) Mo1 side with Cu foil interlayer; (c) 93W side and (d) Mo1 side with Cu film interlayer.
6
4. Conclusions In summary, using Cu interlayer to join 93W and Mo1 alloys by PAS is very successful. For the 93W/Cu foil/Mo1 joint, the average shear strength is 148.4 MPa. Cu atoms can diffuse into the Fe-Ni binder of 93W alloy easily, which contributed to high strength of the 93W/Cu foil/Mo1 joint at 850 °C. Fracture of the 93W/Cu foil/Mo1 joint occurs on Cu foil/Mo1 interface. 93W and Mo1 can be bonded well at 700 °C by using a Cu film interlayer, the average shear strength of the joint is 193.3 MPa. Ni atoms in 93W alloy diffuses to the Cu film interlayer forming Cu-Ni alloys which enhances bonding strength. And fracture of the 93W/Cu film/Mo1 joint mostly happens at the Cu-Ni alloy layer. Acknowledgements: This work has been supported by the National Natural Science Foundation of China (No. 51572208), the 111 Project (No. B13035) and the Joint Fund (No. 6141A02022209). References: [1] GS Cho, KH Choe, SY Choi. Mater Res Bul. 2013; 48: 5053-5057. [2] AA Mazilkina, BB Straumala, SG Protasova et al. Mater lett. 2017; 192: 101-103. [3] M Scapin. Int J Refract Met H. 2015; 50: 258-268. [4] M Xia, P Huang, RK Cu, CC Ge. Surf Coat Tech. 2016; 291: 376-381. [5] C.C. Lin, C.H. Shu, C. Chen et al. Int J Refract Met H. 2012; 31: 284-287. [6] F.F. Senea, C.C. Mottab. Mat. Res. 2013; 16: 417-423. [7] J Zhang, Y Xiao, GQ Luo et al. Mater lett. 2012; 66: 113-116. [8] CB Wang, Q Shen, ZG Zhou, LM Zhang. J Mater Sci. 2005; 40: 2105-2107. [9] Morsi K, Moon KS, Kassegne S et al. Scripta Mater. 2009; 60: 745-748. [10] G Bernard-Granger, A Addad, G Fantozzi et al. Acta Mater. 2010; 58: 3390-3399.
7
[11] YJ Guo, GJ Qiao, WZ Jian, XH Zhi. Mat Sci Eng A. 2010; 527: 5234-5240. [12] YY Wang, M Rao, LJ Li et al. Metall Mater Trans. A 2016; 47A:631-636. [13] YF Wang, HY Gao, YF Han et al. J Alloy Compd. 2015; 639: 642-647. [14] SM Schwarz, BW Kempshall, LA Giannuzzi. Acta Mater. 2003; 51: 2765-2776. [15] F. Moszner, C. Cancellieri, M. Chiodi et al. Acta Mater. 2016; 107: 345-353. [16] Z.Y. Wanga, D. Hana, X.W. Li. Mat. Mat Sci Eng. A, 2017, vol. 679; pp. 484-492.
Figure captions: Figure 1 (a) Microstructure of 93W/Mo1 joint; (b) Enlarged BSE image of 93W/Mo1 joint; (c) SEM image of the 93W/Cu foil/Mo1 interface; (d) The elemental area distributions of 93W/Cu foil/Mo1 bonded joint. Figure 2 Surface morphologies of Cu film: (a) Cu film on base metals, (b) Cross-section morphology and elemental distributions on Mo1 side; (c) SEM image of the interface of 93W/Cu film/Mo1 joint; (d) Elemental distributions across the bonded joint. Figure 3 XRD pattern of fracture surfaces of 93W/Mo1 joints with Cu interlayer: (a) 93W side and (b) Mo1 side with Cu foil interlayer; (c) 93W side and (d) Mo1 side with Cu film interlayer.
8
Highlights 1. Cu interlayer was added to join 93W alloy and Mo1 alloy. 2. There were two approaches to adding Cu interlayer, Cu foil and Cu film 3. PAS was firstly used in joining dissimilar 93W alloy and Mo1 alloy. 4. 93W-Mo1 joint with high bonding strength was obtained by low bonding temperature and short holding time.
9
S0167-577X(17)30693-6 http://dx.doi.org/10.1016/j.matlet.2017.04.132 MLBLUE 22553
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
1 April 2017 28 April 2017 28 April 2017
Please cite this article as: M. Rao, L. Zhang, J. Zhang, G. Luo, Q. Shen, Effect of Cu interlayer on joining 93W and Mo1 alloys by plasma activated sintering, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet. 2017.04.132
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.
Effect of Cu interlayer on joining 93W and Mo1 alloys by plasma activated sintering Mei Rao, Liangmeng Zhang, Jiang Zhang*, Guoqiang Luo, Qiang Shen State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, P. R. China * Corresponding author: Tel.: 027-87168806; E-mail: [email protected] Abstract: 93W and Mo1 were bonded with and without Cu interlayer by plasma activated sintering. The bonding temperature was decreased greatly with Cu interlayer. Shear strength of 93W/Cu foil/Mo1 and 93W/Cu film/Mo1 were 148.4 MPa and 193.3 MPa, respectively. Elements were fully diffused at 93W/Cu and Cu/Mo1 interfaces. Fe-Ni binder in 93W alloy has a sound diffusion with Cu interlayer, and Ni enriched in diffusion interface and formed Cu-Ni alloy at the interface of the 93W/Cu film/Mo1 joint, which led to the increasing in bonding strength of joints greatly. Keywords: Cu interlayer, diffusion, plasma activated sintering, microstructure 1. Introduction 93W and Mo1 alloys process an attractive combination of mechanical properties including high temperature strength, high thermal conductivity, low thermal expansion, and excellent performance in neutron flux environments[1,2]. Both 93W and Mo1 are potential candidates for use in aerospace, automotive, military and nuclear technologies[3,4]. Therefore, it is essential to make a investigation on joining 93W and Mo1. However, due to differences in melting point, thermal conductivity of 93W and Mo1 alloys, it is difficult to obtain a good-quality joint[5]. Adding interlayer is an approach to decrease bonding temperature and increase bonding strength. It is reported that W can be bonded to Mo by adding Pa foil and Ni-Mo alloy[5,6]. Copper is ductile metal which has adequate physical contact with base metal. Jian Zhang[7] has reported that shear strength of Cu/Mo joints is 79 MPa. Chuangbin
1
Wang[8] has employed diffusion welding method to join 93W to OFC and firmly welded joint without large distortion or damage is obtained. Plasma activated sintering (PAS) has become widespread in use and attracted considerable attention recently[9,10]. Recently, PAS has been employed as a joining method to weld dissimilar metals. Yajie guo[11] has used plasma activated sintering process to fabricate multilayered Cu/Al composites successfully. PAS is also used in bonding Mg and Al, shortened the bonding time as a result the formation of brittle Mg-Al intermetallics is prevented[12]. In the present 93W alloy and Mo1 alloy were bonded with and without Cu interlayer by using plasma activated sintering process. There were two approaches to adding Cu interlayer, one was to use a 25 µm Cu foil, the other was to deposit Cu films on 93W and Mo1 by using megnetron sputtering. Microstructure and mechnical properities of bonded joints were investigated. 2. Experimental procedure For the experiment, 93W alloy (93 wt% tungsten with nickel and iron as the additives) and Mo1 alloy (Mo ≥ 99.9 wt%) were sliced into planchets of which the dimension were Φ25 mm × 8mm. The Cu foil (Cu ≥ 99.99 wt%) were cut into 25 mm in diameter. Before bonding process, base metals were first burnished in proper sequence with various grades of SiC grit paper, and then cleaned ultrasonically in acetone. Cu films (Cu ≥ 99.99 wt%) about 500 nm in thickness were deposited on 93W and Mo1 surfaces by magnetron sputtering. PAS apparatus (Ed-Pas) was applied to join 93W and Mo1 slices with Cu interlayer which were assembled into a sandwich structure. A compressive load of 9.8 kN, corresponding to a pressure of 20 MPa, was applied before heating. The vacuum pressure was less than 10 Pa. The sylindrical samples were heated to the bonding temperature, holding for 900 s and finally free cooling.
2
To access mechanical properties of joints, MTS - 810 universal machine was utilized to test shear strength of joints at a loading speed of 0.5 mm/s at room temperature. The bonded joints were observed via a field emission scanning electron microscope (FESEM, FEI Quanta 250FEG). And elements distribution at the interface were analyzed with an electron probe micro-analyzer ( EPMA, JXA - 8100) and an X-ray diffraction system (XRD, Rigaku Ultima III). 3. Results and discussion 3.1 Mechanical characterization Table 1 illustrates shear strength of 93W/Mo1 joints with and without Cu interlayer. Without Cu interlayer, the shear strength of 93W/Mo1 joints is 25.4 MPa. Adding Cu foil as an interlayer, the average shear strength of 93W/Cu foil/Mo1 joint fabricated at 850°C reaches 148.4 MPa. By using Cu film interlayer, bonding temperature decreases to 700°C, the average shear strength is 193.3 MPa, nearly twice more than that of Ni-Mo alloy interlayer (ref.[6]). Therefore, by adding Cu interlayer, 93W and Mo1 can not only be bonded at low temperature but also exhibit a substantial improvement in bonding strength. Table 1 Shear strength of 93W/Mo1 joints with and without Cu interlayer
Specimen
Shear
Bonding parameters
strength
Temperature (°C)
Holding time (s)
Pressure (MPa)
93W/Mo1
1000
900
20
23.4±5
93W/Cu foil/Mo1
850
900
20
148.4±10
93W/Cu film/Mo1
700
900
20
193.3±12
(MPa)
3.2. Microstructure characterization Fig. 1(a) and (b) illustrates microstructure of the 93W/Mo1 joint fabricated at 1000 °C. It is obvious that micro-cracks appear at the 93W/Mo1 boundary, indicating that atomic diffusion at the interface is insufficient and it is difficult to join 93W and Mo1 alloy below 1000°C. Fig. 1(c) and (d) shows
3
microstructure and elemental distribution of the 93W/Cu foil/Mo1 bonded joint. In Fig. 1 (c), the 93W/Cu foil and Cu foil/Mo1 interfaces are free of voids, reaction layers or defects. The diffusion coefficient usually reads D=Do exp(-Q/RT), where Do is the diffusion prefactor and Q is the diffusion activation energy [13]. The diffusion activation energy Q Ni-Cu is 41.2 KJ/mol [14], QFe-Cu is 187 KJ/mol [13], while QW-Cu is 257 KJ/mol [15] which is much higher than than of QNi-Cu and QFe-Cu. So from Fig. 1(d), it also can be found that Cu atoms are inclined to diffuse into the Fe-Ni binder.
Fig. 1 (a) Microstructure of 93W/Mo1 joint; (b) Enlarged BSE image of 93W/Mo1 joint; (c) SEM image of the 93W/Cu foil/Mo1 interface; (d) The elemental area distributions of 93W/Cu foil/Mo1 bonded joint. Fig. 2 (a) shows the surface morphologies of the Cu film. Cu grains are strip shaped and of high crystallization. The thickness of Cu film is uniform and about 500 nm (Fig. 2 (b) ), and the diffusion layer between Mo1 base metal and the Cu film is more than 0.5 µm, which means that the mutual diffusion between the Cu film and Mo1 base metal is competent before bonding process. It can be inferred that the deposition of Cu film is a pre-diffusion process between Cu and base metal, as a consequence, the bonding temperature can be decreased greatly.
4
No voids or cracks appear at the 93W/Cu film/Mo1interfaces in Fig. 2 (c), suggesting that the 93W/Mo1 joint with Cu film interlayer is of high quality. There are five regions (marked I, II, III, IV, V) at the 93W/Cu film/Mo1 interface, as it is shown in Fig. 2 (d). Region I and V are the base metal of W and Mo1. The continuous gradient distributions regions II and IV are W-riched and Mo-riched solid solution layers, and region III is a Cu-riched layer. It can be discovered that Cu mostly distributes in the diffusion interface, and Cu has a concentration at the Fe-Ni binder. At diffusion interface the atomic composition is 88.93% Cu, 7.22% Ni and a few Fe, W and Mo, indicating that the possible phase at the Cu-riched area is Cu-Ni alloy dissolved with Fe, Mo and W atoms. According to ref[16], Cu-Ni alloy possess higher stacking fault energies than pure Cu. As a result the ultimate tensile strength of Cu-Ni alloy increases. In the 93W/Cu film/Mo1 joint, Cu-Ni alloy, nearly 8 at% of Ni, formed at diffusion interface, which contributes to the increasing of bonding strength.
Fig. 2 Surface morphologies of Cu film: (a) Cu film on base metals, (b) Cross-section morphology and elemental distributions on Mo1 side; (c) SEM image of the interface of 93W/Cu film/Mo1 joint; (d) Elemental distributions across the bonded joint. Table 2 Elemental compositions of the selected points 1-6 (Marked in Fig.4)
5
Element Composition (at%) Points
W
Mo
Cu
Fe
Ni
Possible Phases
1
100
-
-
-
-
W
2
8.98
-
8.15
30.97
51.90
Fe-Ni(ss, Cu, W)
3
5.90
0.64
85.42
1.55
6.49
Cu-Ni(ss, Fe, W, Mo)
4
0.98
1.02
88.93
1.84
7.22
Cu-Ni(ss, Fe, Mo, W)
5
0.68
67.81
23.82
3.49
4.20
Mo(ss, Cu, Ni, Fe)
6
-
100
-
-
-
Mo
3.3 Fracture analysis Fig.3 displays the XRD pattern of fracture surfaces of 93W/Mo1 joints with Cu interlayer. From Fig.3 (a) and (b), the phase on 93W sides is primarily Cu, and phase on Mo1 sides is mainly Mo, meanwhile very weak peaks of Cu are detected on the fracture surface of Mo1 side. It can be inferred that fracture of 93W/Cu foil/Mo1 joint is mainly occurred at Cu foil/Mo1 interface. For 93W/Cu film/Mo1 joint, the phases on the 93W side are W and Cu (Fig.3(c)), and the phases on the Mo1 side are Mo and Cu (Fig.3(d)). Compared to pure Cu peaks, Cu peaks on the 93W side have a slight deviation, suggesting that the diffusion at the 93W/Cu film/Mo1 interface is adequate and Cu has formed solid solution and enhanced the bonding of 93W and Mo1 alloys. And it can be concluded that the fracture of the 93W/Cu film/Mo1 joint mostly occurs at the Cu solid solution layer.
Fig.3 XRD pattern of fracture surfaces of 93W/Mo1 joints with Cu interlayer: (a) 93W side and (b) Mo1 side with Cu foil interlayer; (c) 93W side and (d) Mo1 side with Cu film interlayer.
6
4. Conclusions In summary, using Cu interlayer to join 93W and Mo1 alloys by PAS is very successful. For the 93W/Cu foil/Mo1 joint, the average shear strength is 148.4 MPa. Cu atoms can diffuse into the Fe-Ni binder of 93W alloy easily, which contributed to high strength of the 93W/Cu foil/Mo1 joint at 850 °C. Fracture of the 93W/Cu foil/Mo1 joint occurs on Cu foil/Mo1 interface. 93W and Mo1 can be bonded well at 700 °C by using a Cu film interlayer, the average shear strength of the joint is 193.3 MPa. Ni atoms in 93W alloy diffuses to the Cu film interlayer forming Cu-Ni alloys which enhances bonding strength. And fracture of the 93W/Cu film/Mo1 joint mostly happens at the Cu-Ni alloy layer. Acknowledgements: This work has been supported by the National Natural Science Foundation of China (No. 51572208), the 111 Project (No. B13035) and the Joint Fund (No. 6141A02022209). References: [1] GS Cho, KH Choe, SY Choi. Mater Res Bul. 2013; 48: 5053-5057. [2] AA Mazilkina, BB Straumala, SG Protasova et al. Mater lett. 2017; 192: 101-103. [3] M Scapin. Int J Refract Met H. 2015; 50: 258-268. [4] M Xia, P Huang, RK Cu, CC Ge. Surf Coat Tech. 2016; 291: 376-381. [5] C.C. Lin, C.H. Shu, C. Chen et al. Int J Refract Met H. 2012; 31: 284-287. [6] F.F. Senea, C.C. Mottab. Mat. Res. 2013; 16: 417-423. [7] J Zhang, Y Xiao, GQ Luo et al. Mater lett. 2012; 66: 113-116. [8] CB Wang, Q Shen, ZG Zhou, LM Zhang. J Mater Sci. 2005; 40: 2105-2107. [9] Morsi K, Moon KS, Kassegne S et al. Scripta Mater. 2009; 60: 745-748. [10] G Bernard-Granger, A Addad, G Fantozzi et al. Acta Mater. 2010; 58: 3390-3399.
7
[11] YJ Guo, GJ Qiao, WZ Jian, XH Zhi. Mat Sci Eng A. 2010; 527: 5234-5240. [12] YY Wang, M Rao, LJ Li et al. Metall Mater Trans. A 2016; 47A:631-636. [13] YF Wang, HY Gao, YF Han et al. J Alloy Compd. 2015; 639: 642-647. [14] SM Schwarz, BW Kempshall, LA Giannuzzi. Acta Mater. 2003; 51: 2765-2776. [15] F. Moszner, C. Cancellieri, M. Chiodi et al. Acta Mater. 2016; 107: 345-353. [16] Z.Y. Wanga, D. Hana, X.W. Li. Mat. Mat Sci Eng. A, 2017, vol. 679; pp. 484-492.
Figure captions: Figure 1 (a) Microstructure of 93W/Mo1 joint; (b) Enlarged BSE image of 93W/Mo1 joint; (c) SEM image of the 93W/Cu foil/Mo1 interface; (d) The elemental area distributions of 93W/Cu foil/Mo1 bonded joint. Figure 2 Surface morphologies of Cu film: (a) Cu film on base metals, (b) Cross-section morphology and elemental distributions on Mo1 side; (c) SEM image of the interface of 93W/Cu film/Mo1 joint; (d) Elemental distributions across the bonded joint. Figure 3 XRD pattern of fracture surfaces of 93W/Mo1 joints with Cu interlayer: (a) 93W side and (b) Mo1 side with Cu foil interlayer; (c) 93W side and (d) Mo1 side with Cu film interlayer.
8
Highlights 1. Cu interlayer was added to join 93W alloy and Mo1 alloy. 2. There were two approaches to adding Cu interlayer, Cu foil and Cu film 3. PAS was firstly used in joining dissimilar 93W alloy and Mo1 alloy. 4. 93W-Mo1 joint with high bonding strength was obtained by low bonding temperature and short holding time.
9