复合细化制备超细晶纯钛热稳定性研究

Thermal stability of ultra-fine grained titanium by combined refining process

用复合细化方法(ECAP+冷轧+旋锻)制备出超细晶纯钛,利用透射电镜(TEM)、万能拉伸机、显微硬度计和扫描电镜(SEM)研究了不同退火温度对超细晶纯钛组织性能的影响.结果表明:复合细化制备超细晶纯钛的晶粒尺寸约为180nm,其抗拉强度达到870 MPa,低温退火时(200~350℃),组织无明显变化,位错密度逐渐降低,晶界逐渐平直清晰,强度和硬度下降较为缓慢,超细晶纯钛的再结晶温度为350~400℃;退火温度高于400℃时,晶粒逐渐长大,超细晶纯钛的硬度显著下降.观察断口形貌可知,超细晶纯钛的断裂形式为韧性断裂,且随着退火温度的升高,等轴韧窝尺寸增大,深度变深.

Ultra-fine grained Titanium were processed by Combined Refining Process(Equal channel angular pressing(ECAP),cold rolling(CR),and rotary swaging(RS))at room temperature.The effect of annealing temperature on microstructure and properties of ul-tra-fine grained Titanium(UFG Ti)were investigated by Transmission Electron Microscope(TEM),universal testing machine,micro-hardness tester and scanning electron microscope(SEM).The results show that the grain average size of UFG Ti is about 180 nm,and ultimate tensile strength of UFG Ti is over 870 MPa.When annealing at low temperature(200~350℃),the microstructure has no ob-vious change,the dislocation density decreased and the grain boundary,ultimate tensile strength and microhardness slightly decreased.The recrystallization temperature ranges from 350℃ to 400℃.When annealing temperature was higher than 400 ℃,grain size of UFG Ti grew significantly,and microhardness decreased obviously.The fracture surface of UFG Ti shows hybrid tough fracture of dimple.With the increase of annealing temperature,the size and depth of dimples increase.