因瓦合金4J36等离子焊接工艺及接头性能

Process and properties of plasma arc welded Invar alloy 4J36

试验采用等离子弧焊设备对4J36因瓦合金板材进行焊接工艺试验,借助光学显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)和洛氏硬度计等手段分析接头的微观组织和力学性能.结果表明,合理的等离子工艺参数下焊接接头成形良好,抗拉强度可达到母材的93.6%;接头基体为γ相,同时存在γ'(Ni3(Al,Ti))强化相;母材为细小的等轴晶,焊缝处呈树枝状结晶且晶粒粗大,热影响区靠近熔池部分的晶粒过热长大,靠近母材部分为均匀细小的等轴晶;焊接接头拉伸断口表现为韧性断裂,硬度最低值出现在热影响区.

Plasma arc welding of 4J36 low-expansion alloy was conducted. The microstructure and mechanical properties of welded joint were analyzed by using optical microscope( OM), scanning electron microscope( SEM),energy spectrum analysis( EDS),X-ray diffraction( XRD),and Rockwell hardness tester. The results indicate that the weld appearance was excellent and the tensile strength of the joint reached 93. 6% of the base metal under appropriate parameters. The microstructure of the weld consisted of austenite with some strengthening phase γ'( Ni3( Al,Ti)). The microstructure of the base metal was fine equiaxed grain,while that around the fusion line had dendrites structure. In the HAZ,the grains near the weld pool grew up due to overheating,but those near the base metal were fine equiaxed grains. The tensile fracture revealed obvious ductile features,and the HAZ had the minimum hardness.