原始晶粒尺寸对ECAP变形纯钛组织性能的影响

Effects of Initial Grain Size on Microstructure and Properties of Pure Ti Processed by ECAP

室温下,对923及1023 K退火1 h所得的不同原始晶粒尺寸的工业纯钛进行ECAP变形。通过TEM、EBSD、室温拉伸和显微硬度测试研究原始晶粒尺寸对ECAP变形纯钛组织性能的影响。探讨纯钛ECAP变形孪生行为和变形机制。结果表明,退火温度越高,原始晶粒尺寸越大。1道次变形后,1023 K退火纯钛的晶粒细化效果更显著。4道次变形后,923 K退火纯钛的组织更细小均匀。随着变形道次的增加,屈服强度不断增大,1道次变形后增幅最大,约为100%,且原始晶粒尺寸越大,强度增幅越大。纯钛ECAP变形机制包括位错滑移和孪生,原始晶粒尺寸越大,孪晶数量越多。

The pure Ti with different initial grain sizes which was annealed at 923 and 1023 K for 1 h was processed by ECAP at room temperature.The influence of initial grain size on microstructure and properties of ECAPed pure Ti was investigated by TEM,EBSD,tensile tests and microhardness tests at room temperature.The twinning behavior and deformation mechanism of pure Ti were also discussed during the ECAP.The results show that the initial grain size of pure Ti increases with increasing the annealing temperature.The grain refinement effect of pure Ti annealed at 1023 K is more significant than that of pure Ti annealed at 923 K after1 pass of ECAP,while the microstructure of pure Ti annealed at 923 K is finer and more uniform than that of pure Ti annealed at 1023 K after 4 passes of ECAP.With the increase of ECAP pass,the yield stress increases,especially after 1 pass with more than 100% implication.The larger the initial grain size,the greater the stress increase.The deformation mechanisms of pure Ti during the ECAP include dislocation slips and deformation twinning,and with the increase of the initial grain size,the number of twins increases.