Microstructural Evolution and Mechanical Properties of Constrained Groove-Pressed 304 Austenitic Stainless Steel

The present work investigates the influence of constrained groove pressing (CGP) on the microstructural evolution and mechanical properties of 304 austenitic stainless steel. CGP shows a significant improvement in mechanical properties such as tensile strength and micro-hardness. XRD analysis shows the transformation of austenite phase into deformation-induced martensite phase which is also confirmed by vibrating sample magnetometer. Finite element analysis employing Deform 3D software shows the average induced strain of 2.29, after two passes of CGP. Rietveld refinements on XRD patterns affirm the decrease in crystallite size, increase in microstrain and dislocation density. EBSD also shows the formation of substructures due to CGP. The ultimate tensile strength of solution-treated specimens enhances from 729 to 1058 MPa, and the value of micro-hardness increases from 238 to 477 VHN after two passes of CGP. The augmentation in mechanical properties is attributed to the synergic effect of increased dislocation density, martensitic transformation, substructure formation and reduced crystallite size.