电脉冲短时热处理对等轴组织热轧TC4组织转变和绝热剪切特性的影响

Effects of Electric Pulse Heat Treatment on Mechanical Properties and Adiabatic Shear Banding of Hot-rolled Equiaxed TC4 Alloy

研究了不同温度及保温时间电脉冲热处理对等轴组织热轧TC4钛合金微观组织和力学性能的影响。研究发现,电脉冲热处理能在5 min内将材料的原始等轴组织转变成魏氏组织,且温度越高,组织转变所需的时间越短;在组织转变前,原始热轧组织发生了一定程度的再结晶,转变成魏氏组织后晶粒随着温度的升高及保温时间的延长而长大。电脉冲热处理后的材料其准静态压缩塑性和动态压缩塑性均显著提高,绝热剪切敏感性显著降低,且随着热处理温度的升高及保温时间的延长,材料的准静态和动态压缩塑性呈现下降的趋势。经过1000℃/5 min电脉冲处理的钛合金综合力学性能最好,与原始热轧TC4钛合金相比,绝热剪切临界破坏应变提高了133%,绝热剪切破坏的临界单位体积吸收功提高了192%。

The effects of electric pulse heat（EPH） treatment on microstructures and mechanical properties of hot-rolled equiaxed TC4 alloy were investigated. Results show that the original equiaxed microstructure of hot-rolled TC4 alloy turns into the typical lamellar microstructure through EPH within 5 min, and the time microstructure transformation needs becomes shorter with the increasing heat treatment temperature. Recrystallization happens in the equiaxed microstructure before microstructure transformation; after microstructure transformation, the prior beta grains grow with higher temperature and longer holding time. The results of quasi-static and dynamic compression tests indicate that the fracture strain value of alloys after EPH treatment is significantly improved, which decreases with the increasing temperature and holding time, while the susceptibility to the adiabatic shear bands（ASBs） of the hot-rolled TC4 titanium alloy is obviously decreased. Compared with the original hot-rolled titanium alloy, the adiabatic shear fracture strain of the alloy after EPH treatment at 1000 ℃ for 5 min is increased by 133%, and the energy absorbed by materials before adiabatic shear failure is increased by 192%.