表面纳米化TC4合金微观组织的演化

利用超声喷丸(USSP)技术对TC4钛合金进行表面纳米化处理,并采用X射线衍射(XRD)仪、金相显微镜(OM)和透射电镜(TEM)对处理试样的晶粒尺寸、微观应变、微观组织及其演变过程进行了分析。结果表明:随着USSP处理时间的延长,表层晶粒尺寸由15 min的55 nm降低到60 min的26 nm左右,而微观应变则由0.173%增加至0.263%。随塑性变形量的增加,表层位错密度增加,进而形成位错墙、位错胞,并逐步形成亚晶;变形量进一步增加,晶粒继续细化、取向差逐渐增大得到随机分布的纳米晶,从而获得了具有梯度结构的表面纳米化TC4合金。

Microstructure Evolution of TC4 Alloy during Nanocrystallization Process

The TC4 samples have been processed using ultrasonic shot peening (USSP), and X-ray diffractometer (XRD), optical microscope (OM) and transmission electron microscopy (TEM) have been used to analyze the crystallite size, microstrain and microstructure evolution. The results indicate that the crystallite size of the treated surface layer can be decreased to 26 nm from 55 nm as the process duration increases from 15 min to 60 min, and the corresponding microstrain increases from 0.173% to 0.263%. With the strain increasing, the dislocation density of the surface layer increases, and the dislocation wall as well as dislocation cell can be developed to accommodate the strains, then resulting in the formation of subgrains. With further increasing strains, grains are continuously refined, misorientations increase, and the refined grains become random, and finally the TC4 samples with gradient nanostructured surface layer are obtained