热处理对TiAl基合金喷丸试样组织与性能的影响

TiAl合金在高温下服役时，表面因受循环载荷而容易产生疲劳裂纹，因此有必要进行表面处理以改善其力学性能。使用直径0.2 mm钢丸在0.7 MPa气压下对TiAl合金进行室温喷丸实验，使用ABAQUS有限元分析软件进行喷丸仿真模拟研究。随后，对喷丸试样进行不同温度和保温时间的热处理。通过SEM观察TiAl合金纵截面的显微组织，使用X射线残余应力仪测量TiAl合金表面的残余压应力，使用显微硬度仪测量热处理后TiAl合金表面的显微硬度。结果发现，喷丸后TiAl合金表面出现许多凹坑和层片状突起，次表面处发生明显塑性变形并出现许多变形孪晶。热处理后TiAl合金表面残余压应力会随着保温时间的增加和热处理温度的升高而变小。硬度几乎表现出与残余应力相同的趋势，但当热处理温度为1 200℃时，因金相组织发生变化，α₂相含量明显增多，导致硬度增加。

Effect of heat treatment on the organization and properties of TiAl-based alloy shot-peened specimens

Because TiAl alloys are susceptible to fatigue cracking on their surfaces due to cyclic loading when used at high temperatures, it is necessary to treat their surfaces to improve their mechanical properties. In this study, TiAl alloy was subjected to shot peening tests at room temperature, using 0.2 mm diameter steel shots at 0.7 MPa air pressure. The shot peening simulation studies were conducted using ABAQUS finite element analysis software. Subsequently, the shot-peened specimens were heat treated at different temperatures and holding times. The cross-sectional microstructures of the specimens were observed using a scanning electron microscope (SEM), the residual compressive stresses on the surfaces were measured using an X-ray residual stress meter, and the surface microhardness after heat treatment was measured using a microhardness meter. The results showed that many pits and lamellar protrusions appeared on the surface of TiAl alloy after shot peening, and obvious plastic deformations and numerous deformation twins appeared at the secondary surface. The residual compressive stress on the surface of the TiAl alloy after heat treatment decreased as the holding time and heat treatment temperature increased. Hardness followed a similar trend as the residual stress; however, when the heat treatment temperature was raised to 1 200 ℃, the hardness increased due to the change of metallographic organization and a significant increase inα₂ phase content.