Cyclic behavior of gradient microstructure generated by Surface Mechanical Attrition Treatment for an austenitic stainless steel

Abstract : Low cycle fatigue (LCF) behavior of materials processed by SMAT (Surface Mechanical Attrition Treatment) was studied for a stainless steel 316L. SMAT was used to generate gradient microstructure in cylindrical fatigue specimens. Fully reversed strain controlled LCF tests were performed with different strain amplitudes. Hysteresis loops corresponding to different depths from the treated surface were indirectly obtained from the loops obtained by the fatigue tests for SMAT treated and untreated specimens. The results show that the influence of SMAT on cyclic behavior of material is effective mainly during the first several cycles, and it is gradually reduced with the increase of number of cycles. The results also show that SMAT causes the decrease of life in the case where the imposed strain amplitude is high. According to the analysis based on energy dissipation theory, this fatigue life decrease of the SMAT processed specimens could be due to the higher energy dissipation rate in the SMAT affected region.