TC4钛合金惯性摩擦焊接头组织及断裂韧性与裂纹扩展特性分析

Analysis of microstructure, fracture toughness and crack propagation characteristics of inertial friction welding joint in TC4 titanium alloy

摘要:

文章采用了XRD、SEM、EBSD等显微表征技术分析了焊态及焊后热处理态下焊接接头各区域的微观组织特征,并研究了焊接接头的断裂韧性和疲劳裂纹扩展性能。结果表明,焊缝区以再结晶组织为主,热力影响区等轴状初生α_p相转变为棒状结构,热影响区组织与母材基本相同,热力影响区与热影响区的原始β晶粒内部分区域形成了取向差角度约为60°的针状马氏体α′相,热处理促进了残余亚稳态β相分解,在片状α_s相间形成了大量断续分布组织。焊缝区α晶粒内大量的平行或交叉分布的片状α相和复杂的相界面结构可有效阻碍裂纹的扩展并改变裂纹的扩展路径,提高焊接接头的断裂韧性及抗疲劳裂纹扩展能力。

Abstract:

The XRD, SEM, EBSD were used to analyze the microstructure characteristics in different zone of welded joints in the welding state and post-welding heat treatment state, and the fracture toughness and fatigue crack propagation properties of welded joints were researched. The results show that the weld zone is main consisted of recrystallization organization. The equiaxed prior α_Pphase transform the rodlike structure in thermo-mechanically affected zone. The microstructure of the heat affected zone is basically the same base metal. The acicular martensite α" phases with cross angle of approximately 60° are formed within part original β grains in thermo-mechanical affected zone and thermal affected zone. After post-weld heat treatment, the residual metastable β phase was decomposed and a large number of discontinuous microstructure were formed between lamellar α_S phase. A large number of parallel or cross distributed flake α phases and complex phase interface structure within the α grains in weld zone can effectively hinder the crack propagation and change the crack propagation path, and fracture toughness and fatigue crack propagation resistance of welded joints are improved.