Strain relaxation in a Linear Friction Welded Ti alloy

Linear Friction Welding (LFW) can achieve the high integrity joints required for lightweight fan blade and disk assemblies in future more efficient aeroengines. However, the process generates residual stresses that limit component life. Stress relaxation through post weld heat treatment (PWHT) is effective, but insufficient is currently known about how the varying microstructure affects the local relaxation rate for optimal PWHTs to be defined. This proposal seeks to perform in situ measurements of strain relaxation during PWHTs of Ti-6Al-4V LFW welds at temperatures representative of those being considered in industrial practice whilst accounting for the spatial variations in both microstructure, properties and residual stress across the weld.

线性摩擦焊（Linear Friction Welding, LFW）可制备未来高效航空发动机轻量化风扇叶片与盘组件所需的高完整性焊接接头。但该工艺会产生残余应力，进而限制构件的服役寿命。采用焊后热处理（Post Weld Heat Treatment, PWHT）实现应力松弛的方法虽有效，但目前对于微观结构变化如何影响局部松弛速率以确定最优焊后热处理工艺的认知仍较为匮乏。本项目拟针对Ti-6Al-4V线性摩擦焊焊件，在工业实践中常用的典型热处理温度下，开展焊后热处理过程中的应变松弛原位测量，并同步考量焊件整体微观结构、性能与残余应力的空间分布差异。