Influence of shot peening condition on surface amorphization/ nanocrystallization in TiNi shape memory alloy

Abstract

Evolution of surface roughness and microstructure in Ti-50.9 mol%Ni shape memory alloy by shot peening were investigated by X-ray diffractometry and transmission electron microscopy. The crystallite size decreased significantly by shot peening of 30 s and remained essentially unchanged after longer peening. TEM observations of the deformed surface layer revealed the formation of amorphous and nanocrystalline in the samples after shot peening for 20 s. In the area with the lower extent of deformation, {114} B2 deformation twins and thin amorphous bands parallel to the twins were found. It implies that the amorphization occurs preferentially along the twin interfaces. © 2006 The Japan Institute of Metals.