热处理对锻造β凝固γ-TiAl合金组织演变与力学性能的影响

Microstructural evolution and mechanical properties of forgedβ-solidifiedγ-TiAl alloy by different heat treatments

研究不同热处理制度锻态Ti-42Al-5Mn合金的组织和拉伸性能演变行为。结果表明,当锻态合金在800℃时效24 h时,片层间距和γ相晶粒尺寸均增加。而经1300℃处理,然后在800℃时效24 h时,合金片层间距和γ相晶粒尺寸变化不大,由此获得合金理想的高温处理温度区间1250~1300℃,处于β+α区。在该最佳高温处理温度区间1250~1300℃处理后再经1000℃时效处理,合金的强度和塑性均优于同样高温处理后再经800℃时效处理的合金。1000℃时效处理在片层组织晶团界面处诱发析出的β_(o,sec)相是合金强度提高的重要原因,而片层组织晶团界面处析出的~6μm γ相晶粒是合金更高塑性的主要原因。

The microstructural evolution and tensile properties of a forged Ti−42Al−5Mn alloy subjected to different heat treatments were studied.The results showed that,when the forged alloy was aged at 800℃ for 24 h,the interlamellar spacing(λ)andγgrain size at colony boundaries are generally coarsened.Whereas,when the alloy was first annealed at 1300℃ and then aged at 800℃ for 24 h,this coarsening of related microstructures appears less pronounced.The suggested annealing temperatures for the forged Ti−42Al−5Mn alloy are in the range of 1250−1300℃.It was found that,on the condition of the same annealing system,both the strength and ductility were improved as the aging temperature changed from 1000 to 800℃.The secondary precipitatedβo(β_(o,sec))at colony boundaries could be responsible for improving the strength,and theγphase at colony boundaries with the grain size about 6μm might be one of the main reasons for the better ductility.