Study on Microstructure and Mechanical Properties of Electroassisted Solid-state Pressure Welding of Copper and Stainless Steel

doi:10.3969/j.issn.1004-132X.2026.08.024

Abstract

Abstract:

To address the challenges encountered in conventional welding techniques for joining dissimilar metals， this study successfully joins copper and stainless steel via an electrically assisted solid-state pressure welding method. A comprehensive investigation is conducted to elucidate the influence of current intensity on the microstructural evolution and mechanical properties of the welded joint， using microstructural characterization and mechanical testing. The results reveal that， although variations in current intensity do not directly cause pronounced changes in the depth of the interfacial diffusion layer， the synergistic effect of pressure level and current density significantly affects the phase composition and grain refinement at the welding interface， leading to asymmetric microstructural transformations between the copper and stainless steel substrates. Under low current intensities， an irregular Cu-Fe solid solution forms at the interface， acting as a stress concentration zone and thereby reducing the overall joint strength. In this case， fracture tends to occur along the interface， with a minimum shear strength of approximately 60 MPa. Under increased current intensities， a thin， uniformly dispersed， and densely packed interfacial region with an iron- based face-centered cubic （FCC） lattice structure emerges， markedly enhancing the interfacial bonding strength. However， as the current intensity further increases， the copper base metal undergoes accelerated annealing and recrystallization， resulting in substantial grain growth from 11.62 μm to 63.11 μm. Consequently， during tensile testing， the fracture location shifts to the transition zone within the copper base metal， where the tensile strength of pure copper is approximately 185 MPa. This study provides critical experimental insights for optimizing the parameters of electrically assisted solid state pressure welding， thereby advancing the development and industrial applicability of dissimilar metal joining technologies.

Key words: solid-state welding, copper, stainless steel, electric current intensity, microstructure

摘要：

鉴于传统焊接方法在异质金属铜和不锈钢焊接中面临的挑战，通过电辅助固相压力焊接这一新型固相焊接技术成功实现了异质金属铜和不锈钢的焊接。通过微观结构表征与力学性能测试手段，系统研究了电流强度对铜-不锈钢焊接接头微观组织演变和力学性能的具体影响。实验结果表明，尽管电流强度的变化未直接引起界面扩散层深度的显著变化，但它在不同压力与电流密度组合下的综合效应对焊接界面的物相构成及晶粒细化程度产生了显著影响，诱导了铜与不锈钢母材间不对称的微观组织演变现象。在低电流强度条件下，焊接界面处形成了不均匀的铜铁固溶体，该结构特征成为应力集中区域，进而削弱了接头的整体强度，断裂模式倾向于沿界面发生，最小剪切强度约60 MPa；在高电流强度条件下，界面区域形成了一层细小且均匀分布的、具有铁基面心立方（FCC）晶格结构的致密层，此结构有效增强了界面结合强度。然而，随着电流强度的增加，铜侧母材经历了快速的退火再结晶过程，导致晶粒尺寸显著增大（由初始的11.62 μm增至63.11 μm），最终使接头在拉伸过程中断裂位置转移至铜侧母材的过渡区域，获得纯铜的抗拉强度约185 MPa。研究结果为优化电辅助固相焊接参数、推动异质金属连接技术的发展提供了重要的实验参考。

关键词: 固相焊接, 铜, 不锈钢, 电流强度, 微观组织

CLC Number:

TG457.1

ZHANG Shengwei, WANG Jingyu, YU Yan, CHEN Hao, GAO Kun. Study on Microstructure and Mechanical Properties of Electroassisted Solid-state Pressure Welding of Copper and Stainless Steel[J]. China Mechanical Engineering, 2026, 37(8): 2049-2057.

张胜伟, 王景雨, 于彦, 陈浩, 高坤. 电辅助固相压力焊接铜和不锈钢的微观组织及力学性能研究[J]. 中国机械工程, 2026, 37(8): 2049-2057.

Figures/Tables 15

Fig.1 Configuration of joint

Tab.1 Chemical composition of SUS304 and C1220（mass fraction）

	Cr	Ni	Mn	Si	C	P	Mo	N	Cu	Fe
SUS304	18.18	8.02	1.06	0.4	0.047	0.031	0.03	0.046	0.04	其余
C1220	-	-	-	-	-	0.04	-	-	99.96	-

Fig.2 Schematic diagram of the experimental set-up and electrode

Fig.3 The cycle diagram of electroassisted solid-state pressure welding

Tab.2 Electric current parameters for different joints

持续电流

强度I_C/kA

初始通电

时间t_HI/s

冷却时间

t_C/s

脉冲循环次数

Fig.4 Temperature variation during joining recorded by an infrared thermal imaging camera

Fig.5 Temperature-time curve and compressive force-displacement curve

Fig.6 Micro-hardness of Cu and SUS304 for base metal and different joints

Fig.7 Joint appearance and cross-section of joint and joint tensile test results

Fig. 8 Cross-section， SEM image， EDS area mapping and line scan analysis of J-L joint and J-H joint

Fig.9 EDS point analysis at different positions of J-L joint

Fig.10 EDS point analysis at different positions of J-H joint

Fig.11 Microstructure characteristics of SUS304 and Cu BMs

Fig.12 Microstructure characteristics of J-L and J-H joint

Fig. 13 Microstructure characteristics at joint interface for J-L and J-H joints

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