基于快速多重旋转碾压的纯钛表面纳米化

Surface nanocrystallization of pure titanium induced by fast multiple rotation rolling

为了提高纯钛表面的力学性能,采用快速多重旋转碾压(FMRR)技术对其表面进行剧烈塑形变形处理。利用X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)及显微硬度计研究了FMRR处理后纯钛表层的微观结构及其硬度。结果表明:FMRR处理后,纯钛的X射线衍射峰均发生明显的宽化,其主要原因是由于剧烈塑性变形导致晶粒细化及产生的微观残余应力所引起的。纯钛经过FMRR处理20 min后,最表层的晶粒被细化到平均大约22 nm,当处理时间增加到40 min时,样品表层的平均晶粒尺寸进一步减小到大约10 nm。处理后样品表层的显微硬度随着处理时间的增加显著提高,最大可达242 HV,比原始样品提高了74%,其主要是由于晶粒尺寸细化及塑性变形引起的加工硬化所致。

The surface of pure titanium was treated by severe plastic deformation via fast multiple rotation rolling （FMRR） to improve its mechanical properties. Mierostrueture and hardness of the surface layer after FMRR treatment were analyzed by means of X-ray diffractometry （XRD） , high resolution transmission electron microscopy （HRTEM） and microhardness test. The results show that the diffraction peaks of the treated samples are much broader than those of the original sample due to a combined results of grain refinement and microstrain. The average grain size of the surface layer decreases to about 22 nm after FMRR treatment for 20 rain. With the further increase treatment time （40 min）, the grains are refined to about 10 nm. The surface microhardness of FMRR specimen remarkably increases with the increasing of treatment time, and the maximum value reaches 242 HV, which is 74% higher than that of the original sample. The improvement of hardness can be attributed to the grain refinement and the work-hardening during severe plastic deformation.