Characterization of Defects in Deformed Femnsicrni Shape Memory Alloys

The FeMnSi-based shape memory alloys (SMAs) have attracted much attention in the recent time because of their low cost and excellent workability. In this work the deformation-induced defects and phase transformation is investigated by the positron annihilation lifetime spectroscopy (PALS) for Fe-Mn-Si-Cr-Ni samples with different deformation degrees (0%, 5% and 10% deformation). The positron-lifetime spectra were fitted using two components. The trapping component has a positron lifetime around 150 ps related to dislocations. The concentration of defects in the high deformed sample (10%) was found to be higher than the 5% deformation sample. The light optical microscopy (OM) is used to investigate the different phases in samples. The OM shows that the γ→ε martensite phase transformation in the 10% deformation is significantly higher than the one in the 5% sample.