摘要
7075 Al alloy and AZ31B Mg alloy were joined by diffusion welding technique at pressure 29 MPa with various welding temperatures and durations. Scanning electron microscopy examination, shear tests and microhardness evaluation were conducted on the samples interface to find out the effect of welding temperatures and durations on the weldability. The results demonstrate that the AZ31B Mg/7075 Al composite plates are bonded well and the intermetallic phases such as Al_（12）Mg_（17） and Al_（3）Mg_（2） within the joint zone form. It is found that due to the grain coarsening and the formation of brittle compounds, high welding temperatures and long welding durations result in a decrease of shear strength and increase of interfacial welding hardness. The minimum shear strength of 15 MPa along with the maximum microhardness of HV 176 are obtained for the diffusion couple processed at 450 °C for 120 min. It is revealed that enhancing the temperature and choosing appropriate holding time makes a remarkable increase of interfacial welding thickness. Increasing the welding temperature from 430 to 450 °C along with long welding duration（120 min） results in the increase of interfacial welding thickness by 26% where this value is 6% at the welding performed for 60 min.
在压力29 MPa、不同焊接温度和焊接时间下,采用扩散焊技术连接7075铝合金和AZ31B镁合金。对样品界面进行扫描电镜观察、剪切测试和显微硬度测试来研究焊接温度和焊接时间对可焊性的影响。结果表明:7075铝合金/AZ31B镁合金复合板材被很好地连接在一起,且在焊合区形成金属间化合物如Al_(12)Mg_(17)和Al_3Mg_2。由于晶粒粗化和脆性化合物的形成,升高焊接温度和延长焊接时间会导致剪切强度降低和界面焊接硬度增加。在450°C焊接120 min得到的扩焊接接头具有最小的剪切强度(15 MPa)和最大的显微硬度(HV 176)。提高焊接温度且选择合适的焊接时间能显著地提高焊接界面层厚度。将焊接温度从430°C提高到450°C,焊接时间为120 min时,焊接界面层厚度增加了26%,而当焊接时间为60 min时,界面层厚度增加了6%。
