焊后热处理对Ti180电子束焊接头组织与性能的影响

Effects of post-weld heat treatment on microstructure and properties of Ti180 electron beam welded joints

对7 mm厚Ti180双相钛合金电子束焊接接头采用不同焊后热处工艺(550~700℃,8 h),研究热处理温度对接头的显微组织和力学性能的影响。结果表明:热处理后Ti180电子束焊接头焊缝区和热影响区的残余β相上生成纳米级针状α相和球状亚微米级颗粒Ti5Sn3。随着热处理温度的升高,次生针状αʹ相逐渐减少,纳米级针状α相逐渐粗化,球状亚微米级颗粒逐渐回溶,使得接头的焊缝区和热影响区的显微硬度逐渐减小。此外,接头的常温抗拉强度和伸长率逐渐下降,而高温抗拉强度和伸长率整体上呈现随热处理温度先下降后上升的变化趋势。在热处理参数为550℃、8 h时,Ti180焊接接头具有最优的力学性能。且焊后热处理可以显著减小Ti180焊焊接接头的残余应力,在热处理温度为650℃时,接头的残余应力消除效果最佳。

The study aimes to investigate the influence of heat treatment temperatures on the microstructure and mechanical properties of electron beam welded joints in the 7 mm thick Ti180 dual-phase titanium alloy.To achieve this,the different post-weld heat treatments(550−700℃,8 h)were carried out on the welded joints.The results show that heat treatment leads to the formation of nano-scale needle-likeα-phase and spherical submicron-particles Ti5Sn3 on the residualβ-phase in the weld zone and heat-affected zone of the Ti180 electron beam welded joint.As the heat treatment temperature increases,the number of secondary acicularαʹphases gradually decreases,the nanoscale acicularαphases gradually coarsen,and the spherical submicron particles gradually dissolve back into the matrix.Consequently,this results in a gradual decrease in the microhardness of the weld zone and heat-affected zone of the joints.The room-temperature tensile strength and elongation of the joint gradually decrease.However,there is an initial decrease followed by an increasing trend in the high-temperature tensile strength and elongation as the heat treatment temperature increase.Optimized mechanical properties of Ti180 welded joints is acquired at heat treatment parameters of 550℃,8 h.And post-weld heat treatment plays a crucial role in reducing the residual stress of Ti180 welded joints.The optimum residual stress relief effect is achieved at a heat treatment temperature of 650℃.