Microstructural Modification and Tensile Behavior of IF Steel Processed through Surface Mechanical Attrition Treatment

Abstract

The present investigation deals with the impact of surface mechanical attrition treatment (SMAT) on the surface roughness, microstructure, phase stability, hardness, and tensile properties of interstitial-free (IF) steel. SMATed IF steel was characterized by visible-light microscopy, x-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy, and microindentation and tensile testing. The grain refinement and strengthening of the IF steel were found to be dependent on the duration of SMAT. The optimal combination of strength and elongation was observed in the IF steel SMATed for 200 s, showing a microhardness gradient up to a depth of ~ 900 µm and peak surface hardness of 2.6 GPa. The 0.2% yield strength of the IF steel was increased by ~ 125% with an appreciable elongation (~ 44%) almost comparable to that of the untreated material. Furthermore, IF steel SMATed for 200 s followed by stress relief at 300°C and 500°C was found to exhibit thermally stable gradient microstructures with good strength and ductility.