Positron annihilation studies in plastically deformed Fe-Mn-Si-Cr-Ni-C

Fe-Mn-Si-Cr-Ni-C samples with deformations from 2 to 20% were investigated using positron annihilation spectroscopy, optical microscopy (OM) and X-ray diffraction (XRD). Both Doppler broadening of the annihilation radiation (DBAR) and positron annihilation lifetime spectroscopy (PALS) measurements were performed. The DBAR experiments, carried out using a slow positron beam, indicate a sudden increase in the defect concentration in between 4 and 6% deformation. This is confirmed by the lifetime measurements. In between 6% and 8% deformation the lineshape parameter significantly changes which coincides with the drastic increase of the concentration of the martensite phase as confirmed by XRD. Positron annihilation spectroscopy indirectly probe the gamma/epsilon martensitic phase transformation by probing correlated dislocations.