应变速率对TB15钛合金软化机制的影响

Effect of strain rate on softening mechanism of TB15 titanium alloy

采用Gleeble-3500热模拟试验机对TB15钛合金在变形温度810~930℃、应变速率0.001~10 s^(-1)范围进行等温热压缩实验,基于实验数据分析了不同应变速率下TB15钛合金的流动软化行为,并结合微观组织和变形激活能Q研究了应变速率对其软化机制的影响。结果表明:合金的流动软化程度在不同应变速率范围内的变化规律不同;微观组织和变形热效应是造成流动软化的主要原因,变形热效应在高应变速率(ε≥0.1 s^(-1))范围内的影响更为显著;通过微观组织分析可知,动态回复(DRV)在热变形过程中占主导地位,低应变速率(ε<0.1 s^(-1))下的主要软化机制为DRV和动态再结晶(DRX),随着应变速率的升高,DRX程度降低,且应力集中作用加强,变形带在高应变速率下被激活,这在一定程度上有利于晶粒细化。低应变速率和高应变速率的变形激活能分别为213.8 kJ/mol和255.3 kJ/mol,低应变速率下的微观组织软化效应更加明显。

The isothermal compression tests of TB15 titanium alloy were carried out at deformation temperature of 810−930℃and strain rate of 0.001−10 s^(-1) by Gleeble−3500 thermal simulation machine.Based on the experimental data,the flow softening behavior at different strain rates was analyzed,and the influence of strain rate on the softening mechanism was studied by combining the microstructure and the deformation activation energy Q.The results show that the variation laws of flow softening degree of alloys in different strain rate ranges are different.The microstructure and deformation thermal effects are the main causes of flow softening,and the effect of deformation thermal effects is more significant in the range of high strain rate(ε̇≥0.1 s^(-1)).The microstructure analysis shows that the dynamic recovery(DRV)dominates the hot deformation process.The main softening mechanisms at low strain rates(ε̇<0.1 s^(-1))are DRV and dynamic recrystallization(DRX).With the increase of the strain rate,the degree of DRX decreases and the stress concentration is strengthened.The deformation bands are activated at high strain rate,which is beneficial to grain refinement to a certain extent.The kinetic analysis shows that the deformation activation energies of low strain rate and high strain rate are 213.8 kJ/mol and 255.3 kJ/mol,respectively.The softening effect of microstructure is more obvious in the low strain rate range.