应变速率对TC21钛合金超塑性拉伸微观组织的影响

Influence of Strain Rate on Superplastic Tensile Microstructure of TC21 Titanium Alloy

研究了应变速率对TC21钛合金超塑性拉伸过程中应变速率敏感性指数m值及显微组织的影响。结果表明,m值在温度为900℃,初始应变速率为10-4～10-2s-1时均大于0.3,在初始应变速率为3.3×10-4s-1时,m值达到了最大,平均值为0.376。在较快初始应变速率条件下拉伸时,在温度和较大变形程度的作用下,试样变形区发生了动态再结晶,形成了很多细小、等轴的晶粒,在最佳初始应变速率及更慢速条件下拉伸时,由于高温长时间大变形的作用,试样变形区发生了明显的聚集再结晶长大,相当一部分晶粒合并长大成片状。

The influences of strain rate on strain rate sensitivity m and microstructure were studied during TC21 titanium alloy superplastic tensile. The results indicate that strain rate sensitivity m is more than 0.3 at 900℃ and initial strain rate of 10^-4-10^-2 s^-1, and attains maximum at 3.3×10^-4 s^-1 , the average value is 0.376. At high initial strain rate tensile, dynamic recrystallization happens and many fine and equiaxled grains form at deformed area of sample due to the effect of temperature and large deformation. At the best and slower initial strain rate, collective recrystallization happens obviously and many grains grow up into plate at deformed area of sample due to the effect of huge deformation at long time and high temperature.