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利用热模拟试样模拟TiNi合金激光焊接接头焊缝热影响区,对焊接接头、焊缝金属、模拟热影响区和母材的相变温度进行差热分析,研究了焊接接头与其它三者逆相变温度的关系,并利用OM,SEM和XRD对母材、热影响区和焊缝金属的组织、析出相的分布以及晶体结构进行了研究.结果表明,TiNi合金激光焊接接头的形状恢复率与母材无明显差别,但形状恢复温度区间与母材差异较大,其形状恢复开始温度比母材低40℃;焊缝金属和热影响区逆相变开始温度(As)和结束温度(Af)均不同于母材,主要原因是焊缝金属经历了熔化-凝固过程,失去了母材中原有的晶体择优取向,且析出相尺寸小、分布不均;而热影响区As和Af降低,可能是细小析出相重新固溶于基体所致.整个接头的逆相变温度区间与焊缝金属近似,调控焊缝金属的相变温度是控制TiNi合金激光焊接接头形状记忆功能的关键.
The heat affected zone (HAZ) of TiNi alloy laser welded joint was simulated by thermal simulation specimen, and the differential thermal analysis of the phase transition temperature of welded joint, weld metal, simulated heat-affected zone and base metal was carried out. The effects of welding joint and other three inverse Phase transition temperature and the distribution of microstructure and precipitated phase in the base metal, heat affected zone and weld metal by OM, SEM and XRD.The results show that the shape recovery rate of TiNi alloy laser welded joints And the base metal no significant difference, but the shape recovery temperature range and the base metal larger, the shape recovery start temperature lower than the base metal 40 ℃; weld metal and heat affected zone reverse transformation start temperature (As) and end temperature ( Af) are different from the base metal, the main reason is that the weld metal undergoes the melting-solidification process, loses the original crystal orientation in the base material, and the precipitated phase has small size and uneven distribution; while the heat-affected zone As and Af decrease , Which may be due to the re-solution of the fine precipitates in the matrix.The phase transition temperature of the entire joint is similar to the weld metal, and the key to controlling the shape memory function of the TiNi alloy laser welded joints is to control the phase transition temperature of the weld metal.