Study of residual stress accumulation in TiNi shape memory alloy during fatigue using EBSD technique

In this study, electron backscatter diffraction (EBSD) technique was applied to study the residual stress accumulation of TiNi shape memory alloy (SMA) during fatigue process, which caused the degradation of the shape memory effect (SME) and super-elasticity (SE). From the analysis of the pattern quality change before and after fatigue test, it showed that, with the stress-induced martensitic transformation (SIMT) during loading process and reverse SIMT during unloading process in each loading cycle, residual stress was accumulated in the parent phase. The results also showed that the residual stress distribution was not uniform inside one grain and between grains. TEM observation showed only dislocation increasing, no persistent slip band (PSB) was found, showing that the non-uniformity of the residual stress distribution was not caused by PSB.