高能喷丸处理对7A52铝合金表面微观组织结构及性能的影响

Effect of High-energy Shot Peening Treatment on Micro-structure and Properties of 7A52 Aluminum Alloy

随着金属表面自纳米化技术的不断发展,金属材料的表面性能得到了明显提升。通过SEM、EBSD、TEM和HRTEM等分析测试手段,对高能喷丸处理后的7A52铝合金表面纳米化机理进行了分析。结果表明,随喷丸时间的延长铝合金表面硬度显著增大,当喷丸时间为50min时,表面硬度约为270HV,与基体相比提高了近1.5倍。此时铝合金外表面均匀分布着平均晶粒尺寸约为14.16nm的等轴晶,距表面约60μm处分布着以小角度晶界为主的微米级亚晶。7A52铝合金表面纳米级晶粒的形成机理主要是:晶粒变形使晶内逐渐形成高浓度位错,位错的缠绕、塞积对基体晶粒进行了初步分割细化,在往复载荷的作用下最终在表面形成了等轴的随机取向分布的纳米级晶粒。

With the development of surface self-nanocrystallization technology of metallic materials,the metallic surface properties have been enhanced to a certain degree.In this paper,the mechanism of surface nanocrystallization on 7A52 aluminum alloy after high-energy shot peening treatment（HESP）was characterized by SEM,EBSD,TEM and HRTEM.The results show that the microhardness increase with the increase of shot peening time.After 50 min HESP,the surface hardness is about 270 HV,which can approximately increase to 1.5times compared to the base metal;the average grain size is about 14.16nm;the subsurface layer of 60μm deep is composed of micrometers sub-grains.The surface layer grain refinement process of 7A52 aluminum alloy involves formation of dislocation pile-up and tangling,which resulted in deformed grains.Finally,nano-scale grains with equiaxed shape and random crystallographic orientations are formed upon the multidirectional repeated loads.