焊接温度对AZ31B/Cu瞬间液相扩散焊接头组织及力学性能的影响

Effects of Welding Temperature on Microstructure and Mechanical Properties of Transient Liquid-phase Diffusion Welded Joint of AZ31B / Cu

以Al为中间层对AZ31B/Cu异种材料进行瞬间液相扩散连接试验,采用SEM观察接头界面扩散区的组织形貌,结合EDS、XRD分析界面区的物相及成分,采用室温拉伸实验机测试接头剪切强度,研究了焊接温度对AZ31B/Al/Cu界面组织和剪切强度的影响。结果表明,加热温度对Al、Mg、Cu元素扩散影响很大,从而对微观组织和剪切强度产生影响。445℃时,Al、Mg元素扩散不充分,Mg/Al界面无法形成共晶液相,界面结合较弱。450℃时,Al箔完全溶解,界面区宽度显著增加,从Mg侧到Cu侧,扩散区的微观组织依次为α-Mg(Al)固溶体、Mg-Al共晶组织、Cu(Al)固溶体,接头强度最高达到53 MPa,约为母材AZ31B剪切强度的33.2%。460℃时,界面扩散区宽度缓慢增大,靠近Cu侧的界面区产生大量脆性Al-Cu化合物,接头强度下降。

A test of transient liquid phase diffusion welding of AZ31B/Cu was carried out with AI foil as interlayer. The mierostructure, morphology, phase and composition of the diffusion interface zone were analyzed by SEM, EDS and XRD, respectively. The shear strength of the joints was tested by tensile testing machine. The effect of welding temperature on the interfacial structures and shear strength of the joints was studied. The results show that the heating temperature has great influence on the diffusion of Al, Mg and Cu elements, which affects the microstructure and shear strength. When the bonding temperature is 445℃, the diffusion of Al and Mg elements is not sufficient, so that eutectic liquid phase cannot form at Mg/Al interface, with an interfacial bond weak. When the temperature is 450 ℃ Al foil is completely dissolved. The width of the interface zone increases significantly. The microstructure of diffusion zone presents as a-Mg （Al） solid solution, Mg-Al eutectic structure and Cu （Al） solid solution in order from Mg side to Cu side. The highest joint strength is up to 53 MPa, about 33.2% of the shear strength of AZ31B. When the temperature is up to 460℃, the width of the interracial diffusion zone slowly increases. A great amount of Al-Cu fragile compounds generates at the interfacial zone near Cu side with the joint strength decreased.