退火对表面纳米化纯钛热稳定性的影响

采用表面机械研磨技术实现纯钛材料表面纳米化,并研究了纳米化处理后的材料表层组织结构,详细分析了样品表层纳米晶组织在不同温度、不同时间退火后的热稳定性.结果表明:纯钛TA2经过表面机械研磨处理后可以在表面形成等轴且取向随机的纳米晶层,晶粒尺寸约为12nm.对表面纳米化样品退火后发现,表层纳米晶组织在773 K以下温度退火后具有良好的热稳定性,晶粒尺寸没有明显增大;在773 K温度退火150min后晶粒尺寸稍有增大,而在773 K温度退火240min后晶粒尺寸明显增大,且横截面显微硬度也比表面纳米化后未退火样品显著下降,良好的热稳定性消失.

Effect of Annealing on Thermal Stability of Nanostructured Surface Layer of Pure Titanium

A nanostructured surface layer was fabricated on a pure Ti plate by surface mechanical attrition treatment(SMAT).The microstructure and thermal stability of the nanocrystallized layer annealed at different temperatures for various times were characterized.It is shown that the coarse-grained structure in the surface layer was refined into equiaxed ultrafine grains(about 12 nm) with isometric and random crystallographic orientations after SMAT.When the annealing temperature was lower than 773 K,little change in grain size was found,indicating satisfactory thermostability.The specimen annealed at 773 K for 150 min showed a slight recrystallization in the surface layer.However,the grain size of the sample increased obviously when it was annealed at 773 K for 240 min,and the value of the surface layer’s hardness along the depth became smaller than that of the un-annealed SMAT specimens,suggesting the excellent thermostability disappeared.