Abstract: In‐plane Electronic Speckle Pattern Interferometry (ESPI) has been successfully used during tensile tests on SMA‐treated (Surface Mechanical Attrition Treatment) and as‐received 316L stainless steel in order to measure the strain rate field. The heterogeneity in the strain rate field can be observed from a stage of deformation which doesn’t coincide with the classic Considère’s criterion (dF = 0) for the diffuse neck initiation (or plastic instability). The initiation of this heterogeneity strongly depends on treatments undergone by the material. In this paper, a comparison was performed about the heterogeneity initiation of specimens SMATed during 30 min with 2 mm shot, 3 mm shot and a non‐treated sample. The formation of the two slip band system until fracture of the tensile specimen was also studied.