焊接温度对Mg/Al扩散焊接头微观组织和性能的影响

摘要

The joining of AZ31B Mg alloy to 6061 Al alloy was investigated at different joining temperatures by vacuum diffusion bonding method.The microstructures of Mg/Al dissimilar joints were studied by means of optical microscopy (OM),scanning electron microscopy (SEM) and energy dispersive X-ray (EDX).The results show that the thickness of each layer in the diffusion zone increases with the increase of joining temperature,and the microstructure changes obviously.At joining temperature of 440 ℃,the diffusion zone is composed of Mg2Al3 layer and Mg17Al12 layer.At joining temperatures of 460 and 480 ℃,the diffusion zone is composed of Mg2Al3 layer,Mg17Al12 layer,eutectic layer of Mg17Al12 and Mg-based solid solution.The width of high-hardness zone in the joint increases with increasing joining temperature,and the micro-hardnesses at different locations in the diffusion zone are csignificantly different.The joining temperature of 440 ℃ offers the highest tensile strength of 37 MPa,and the corresponding joint exhibits brittle fracture at the intermetallic compound layer of Mg17Al12.%采用真空扩散焊在不同焊接温度下对AZ31B镁合金和6061铝合金进行连接.利用光学显微镜(OM)、扫描电镜(SEM)和能谱(EDX)观察Mg/Al异种金属接头的显微组织.结果表明:随着焊接温度的升高,扩散区各层的厚度增加,且组织发生明显变化.440℃时扩散层由Mg2Al3层和Mg17Al12层组成;460和480℃时由Mg2Al3层、Mg17Al12层和Mg17Al12与镁基固溶体的共晶层组成.随着加热温度的升高,高硬度区域显著增多,区域内不同位置的硬度存在明显差别.当焊接温度为440℃时接头的最大抗拉强度为37 MPa,脆性断裂发生在Mg17Al12层.