Ti-22Al-25Nb合金惯性摩擦焊接头显微组织与力学性能

Microstructure and mechanical properties of inertia friction welded joint of Ti-22Al-25Nb alloy

采用惯性摩擦焊技术焊接Ti-22Al-25Nb合金,研究热处理前后焊接接头微观组织和显微硬度的变化,分析接头在650℃和750℃高温拉伸力学性能.结果表明:接头原始态焊合区由B2相和极少量残余α2相构成,热处理后焊合区由B2相和O相构成,O相由B2相直接相变产生,相变过程无成分变化.原始态焊合区的显微硬度高于母材,780℃/3 h热处理后焊合区的显微硬度陡升,大量析出的细小O相促进硬度升高,800℃/3 h热处理后焊合区显微硬度介于原始态和780℃/3 h热处理之间.高温拉伸断裂位置均位于母材区域,650℃拉伸断口微观形貌呈韧性断裂特征,断口存在较多浅而小的韧窝.

The Ti-22 Al-25 Nb alloy was welded by inertia friction welded technology.The micros-tructure and microhardness of welded joints before and after heat treatment were studied.The tensile mechanical properties at 650℃ and 750℃ of welded joints were analyzed.The results show that the weld zone of the as-welded joint consists of B2 phase and a very small amount of residual α2 phase.After heat treatment,the weld zone consists of B2 phase and O phase.The O phase is transformed from B2 phase,and there is no composition change during the phase transition process.The microhardness of the as-welded zone is higher than that of the base material.After heat treatment at 780℃for 3 h,the microhardness of the welded zone increases significantly due to the precipitation of fine O phase.But the microhardness of the welded zone with heat treatment at 800℃ for 3 h is between that of the as-welded state and the heat treatment at 780℃ for 3 h.The specimen of high temperature tensile fracture in the base material,and the tensile fracture morphology presents ductile fracture feature with many small shallow dimples.