焊后热处理对Ti-22Al-27Nb合金激光焊接接头组织与高温性能的影响

Effect of post-weld heat treatment on microstructure and high temperature properties of laser welded Ti-22Al-27Nb alloy

研究焊后热处理对激光焊接2．5mm厚Ti-22A1-27Nb合金组织和高温力学性能的影响。结果表明，Ti-22A1-27Nb合金激光焊接焊缝组织为单一的B2相。焊缝650℃高温抗拉强度为母材的75％，塑性则仅为母材塑性的40％左右。拉伸断口形貌为岩石状，呈现沿晶断裂特征。经过焊后热处理，焊缝组织为B2相＋O相。相对于未热处理接头，热处理后焊缝和热影响区的硬度下降很多并趋于平缓。热处理温度750℃、保温时间1h时焊接接头650℃高温抗拉强度达到了母材的87．5％，塑性为母材的82．2％，接头断裂形式为解理断裂。

Effect of post-welded heat treatment on the microstructure and high temperature properties of laser welded 2.5 mm thick Ti-22A1- 27Nb alloy was investigated. The results show that the weld beam of the welded joint is composed of single-phase B2. The high temperature tensile strength and ductility of the welded joint at 650 T2 are 75% and 40% of that of the base metal, respectively, and the fracture surface shows a rock-like intergranular fracture pattern. After post-weld heat treatment, the weld beam is composed of B2 ＋ O phases. The microhardness values of weld beam and heat affected zone decrease sharply compared with the non-heat treated welded joint. After 750℃×1 h post-weld heat treatment, the tensile strength and ductility of the welded joint at 650 ℃ can reach about 87.5% and 82.2% of that of the base metal, respectively, and the corresponding fractograph exhibits eleavage fracture pattern.