Evolution of microstructure, phase composition and hardness in 316L stainless steel processed by high-pressure torsion

The evolution of phase composition, microstructure and hardness in 316L austenitic stainless steel processed by high-pressure torsion (HPT) was studied up to 20 turns. It was revealed that simultaneous grain refinement and phase transformation occur during HPT-processing. The γ-austenite in the initial material transformed gradually to ɛ-and α’-martensites due to deformation. After 20 turns of HPT the main phase was α’-martensite. The initial grain size of ~42 μm was refined to ~48 nm while the dislocation density increased to ~143 × 1014 m-2 in the α’-martensite phase at the disk periphery processed by 20 turns. The microstructure and hardness along the disk radius became more homogeneous with increasing numbers of turns. An approximately homogeneous hardness distribution with a saturation value of ~6140 MPa was achieved in 20 turns.