FeMnSi shape memory alloys (SMAs) have received much attention as one-way SMAs due to their cost-effectiveness. Variable-energy (0-30 keV) positron beam studies have been carried out on a Fe-Mn-Si-Cr-Ni-C alloy with different degrees of deformation. Doppler broadening profiles of the positron annihilation as a function of incident positron energy were shown to be quite sensitive to defects introduced by deformation. The variation of the nature and the concentration of defects are studied as a function of isochronal annealing temperature. These results are correlated with the data measured with the positron annihilation lifetime spectroscopy (PALS). The positron annihilation results are compared to XRD and optical microscopy (OM). (C) 2008 Elsevier B.V. All rights reserved.