Ti-6Al-2Zr-1Mo-1V合金塑性流动失稳预测

Prediction of Plastic Flow Instability of Ti-6Al-2Zr-1Mo-1V Alloy

摘要:

对Ti-6Al-2Zr-1Mo-1V合金进行等温恒应变速率压缩试验，利用压缩试验数据对比Prasad失稳准则和唯象型失稳准则，发现2种准则均预测出合金在应变速率为0.32~10 s-1范围内的塑性流动失稳现象，该失稳区随变形温度的降低具有逐渐向低应变速率范围扩展的趋势。经微观组织观察发现，Prasad准则不能预测到合金在750~800 ℃，0.001~0.0032 s-1范围发生的局部流动和弯折失稳，而唯象型准则对合金在770~870 ℃、0.01~0.32 s-1和900~950 ℃、0.32~3.16 s-1区域出现的晶界裂纹、孔洞以及局部流动不能进行准确预测。结合2种准则的优缺点，提出预测合金塑性流动失稳的新方法。

Abstract:

Isothermal constant strain rate compression tests were carried out for Ti-6Al-2Zr-1Mo-1V alloy. The plastic flow instability was predicted by Prasad criterion and phenomenological criterion and the results were compared through the compression experiment data. It is shown that the both instability criterions predict a large region of flow instability in the high strain rate range of 0.32-10 s-1, which is likely to extend to low strain rate region with decreasing of the deformation temperature. The corresponding microstructures of deformed specimens were observed. The results indicate Prasad criterion can not predict the flow localization and kinking instability in the range of 750-800 oC and 0.001-0.0032 s-1. However, cracks and cavities at initial β boundaries and flow localization can not be predicted by phenomenological instability criterion in the range of 770-870 oC and 0.01-0.32 s-1, and in the range of 900-950 oC and 0.32-3.16 s-1. A new method to predict plastic flow instability was developed by superimposing the two instability maps of the two criterions on the basis of their merits and drawbacks.