Effect of surface mechanical attrition on microstructure and mechanical properties of hypoeuctectoid steel

Abstract

Effect of ultra-fine structure obtained by surface mechanical attrition treatment(SMAT) on microstructure, yield strength (YS), ultimate tensile strength (UTS) and microhardness of hypoeuctectoid steel have been studied in this paper. Surface alteration has been obtained by vibratory SMAT equipment with particular parameters for similar class of material. The SMAT has been carried out for different time periods such as 10, 20, 30 min. The pearlite and ferrite geometry present has been found intermixed after SMAT process. The microstructure shows a composite structure consisting of fiber/angular cementite particulates dispersed in a ferrite matrix. Thus, these structure obtained at 30 min of SMAT has significantly affected the mechanical properties. The SMAT affected layer has found to be 300μm which shows an increased Young’s modulus from 140 GPa to 246 GPa. The yield stress (YS) and ultimate tensile strength (UTS) has been increased about 6% and 22% , respectively. The surface microhardness of the material has been changed from 226±5 HV0.3 to 405±7 HV0.3 by SMAT, which is attributed to the grain refinement and dispersion of fine carbide particles within the matrix.