热处理对TC21钛合金线性摩擦焊接头组织与性能的影响

基于先进飞机构件研制需求，针对TC21钛合金线性摩擦焊接头，设计了3种热处理制度，开展了焊态及不同热处理状态下接头显微组织及力学性能研究. 结果表明，焊态试样的焊缝区由细化的β晶粒组成，晶内析出含有大量位错的针状马氏体，起到了位错强化作用，显微硬度相比母材明显提高，热力影响区由于次生α相发生了溶解，显微硬度相比母材有所降低. 热处理后焊接接头内的α相发生了显著变化，在高温区退火时，长时间保温导致初生条状α相长大，在低温区退火则促进了次生针状α相的析出；所有热处理后的接头进行拉伸试验后均断裂于母材区，经过双重退火的接头其焊缝区及热力影响区组织均为β转变组织+初生长条状α相 + 次生针状α相，并且各区域显微硬度基本与母材一致，组织更加均匀.

Effect of heat treatment on microstructure and properties of linear friction welded joint of TC21 titanium alloy

Based on the development requirements of advanced aircraft components, for TC21 titanium alloy linear friction welded joint, three heat treatment systems were designed, and the microstructure and mechanical properties of the joint were analyzed under the welding condition and different heat treatment conditions. The results show: the weld zone of the as welded sample is composed of fine β grains, and acicular martensite with a large number of dislocations precipitated in the crystal,which plays a role of dislocation strengthening, the microhardness is significantly higher than that of the base metal. The secondary α phase dissolved in the thermal mechanical affected zone which near the base material, resulted in decrease in microhardness. The α phase in the joints changes significantly after heat treatment. A long holding time of annealing in high temperature zone leads to the growth of primary strip α phase, and annealing in low temperature zone promotes the precipitation of secondary needle α phase. All tensile specimens after heat treatment are broken in the base material area, the microstructure of weld zone and thermo-mechanically affected zone of the joint after double annealing is β transformed tissue + primary strip α phase + secondary acicular α phase, the microhardness of each region is basically the same as that of the base metal, and the microstructure is more uniform.