Mg-Al-Sn钎料及其AZ61A镁合金钎焊接头组织性能分析

采用扫描电镜、X射线衍射分析、热分析等手段分析了Mg58.5Al31.5Sn10和Mg58.5Al31.5Sn10RE两种钎料及其钎焊AZ61A镁合金对接接头组织性能. 结果表明，Mg58.5Al31.5Sn10钎料及其钎缝组织主要由块状Mg2Sn和(Mg17Al12+Mg2Sn)二元共晶相组成，并含有少量三元共晶相(Mg17Al12+Mg2Sn+α-Mg). Mg58.5Al31.5Sn10RE钎料及其钎缝组织中未发现块状Mg2Sn相，其组织主要由(Mg17Al12+Mg2Sn+α-Mg)三元共晶和(Mg17Al12+Mg2Sn)二元共晶相及少量Al-RE组成. 和Mg58.5Al31.5Sn10钎料相比，Mg58.5Al31.5Sn10RE组织更加均匀细小，固液相线温度明显降低，熔程缩短了6 ℃，铺展面积提高了5.4%，对接接头平均抗拉强度提高了8.6%，二者拉伸断口形貌均呈现为脆性断裂.

Microstructure and properties of Mg-Al-Sn filling metal and solder joint of AZ61A magnesium alloy

The filling metals of Mg58.5Al31.5Sn10 and Mg58.5Al31.5Sn10RE were prepared. The microstructure and properties of the filling metals and the corresponding butt joints of AZ61A magnesium alloy were investigated by analysis methods including SEM, XRD, DSC, wetting and tensile strength test, etc. The results have shown that the microstructures of Mg58.5Al31.5Sn10 filling metal and its joint mainly consist of massive Mg2Sn, binary eutectic phase of Mg17Al12and Mg2Sn, and a small amount of ternary eutectic phase of Mg17Al12, Mg2Sn andα-Mg. However, the microstructures of Mg58.5Al31.5Sn10RE filling metal and its joint chiefly comprise ternary eutectic phase of Mg17Al12, Mg2Sn andα-Mg, binary eutectic phase of Mg17Al12and Mg2Sn, and a small amount of Al-RE phase. Compared with Mg58.5Al31.5Sn10, the microstructure of Mg58.5Al31.5Sn10RE is more homogeneous and finer, solid-liquid phase line temperatures obviously decrease, the melting temperature range shorts 6 ℃, and the spreading area increases by 5.4%. The butt joint average tensile strength of AZ61A magnesium alloy with Mg58.5Al31.5Sn10RE filling metal raises by 8.6% than that of with Mg58.5Al31.5Sn10RE. The butt joints of both filling metals exhibit the brittle fracture morphology.