纳米压痕法测量超细晶工业纯钛室温蠕变速率敏感指数

室温下,采用复合细化(ECAP+冷轧+旋锻)工艺,制备出平均晶粒尺寸约为180 nm的超细晶工业纯钛,其抗拉强度高达870 MPa。利用纳米压痕仪对超细晶工业纯钛以恒加载速率/载荷的方式进行测试实验,通过测定压头保载阶段的压入位移和材料的硬度值计算得出室温蠕变速率敏感指数m值。结果表明:超细晶工业纯钛由于晶粒明显细化,晶界数量增多,晶界长度增加,位错增殖,在室温下表现出优良的抗蠕变能力,适合在压力环境下长期工作,其蠕变机理主要为蠕变位错机理。室温蠕变速率敏感指数m值与加载条件无关,主要由材料的微观组织决定。

Measurement of Creep Rate Sensitivity of Ultra-fine Grained Commercial Purity Titanium at Room Temperature by Using Nanoindentation

Ultra-fine grained commercial purity titanium (UFG CP Ti) was fabricated by combined refining process (Equal channel angular pressing (ECAP), cold rolling and rotary swaging) at room temperature. The grain average size of UFG CP Ti was about 180 nm, and ultimate tensile strength of UFG CP Ti was over 870 MPa. The nanoindention creep tests of UFG CP Ti were carried out by the nanoindenter with the constant loading rate/load at room temperature. The creep strain rate sensitivity m was determined by using depth and micro-hardness during the holding load stage. The results show that due to the obvious grain refinement, increase of the amount and the length of grain boundaries and the dislocation multiplication, UFG CP Ti shows good resistance to creep at room temperature and its major creep mechanism is the dislocation creep. The values of indentation creep rate sensivities are independent of loading conditions, but are close related to the microstructure of the materials.