纯Ti纳米结构表层的探讨

Investigation of Nanostructured Surface Layer of Pure Titanium

利用表面机械处理技术在纯钛表面制备出50 靘厚纳米表面层, 采用金相显微镜(OM)、透射电镜(TEM)研究了处理层的微观结构。随着应变增加,晶粒逐渐细化。晶粒的细化机制为:孪晶的形成和孪晶碰撞;孪晶转变成取向不同的片状晶;片状晶转变成含有位错的胞状晶、取向不同的小角度块状晶以及取向不同的多边形亚细晶;亚细晶和片状晶转变成纳米晶。微观结构观察证实了动态再结晶促使晶粒细化。

A nanostructured surface layer up to 50 mum thick of commercially pure titanium was produced by a surface mechanical treatment (SMT) technique. The microstructure features of the SMTed surface layer were investigated by cross-sectional OM and TEM. The grain refinement process with the increase of the strain in the surface layer involves: (1) formation of twins and intersection of twin systems, (2) transformation of twins into low disoriented lamellae, (3) division of lamellae into dislocation cells, low-angle disoriented blocks and then highly disoriented polygonal submicronic grains, (4) further fragmentation of submicronic polygonal grains or residual lamellae into randomly oriented nanograins. There is microstructural evidence that a rotation recrystallization mechanism is operative.