High-performance AISI 316L by microstructure engineering

Abstract

In this work, a high-performance AISI 316L was produced by microstructure engineering. Asymmetric turned rolling (ATR) followed by back-annealing at 900 °C for 10, 30, 60, and 120 min was used to achieve a unique microstructure. The results showed that, in the 900-10 and 900-30 samples, there was a microstructure consisting of a thin recrystallized surface layer and a deformed non-surface area. By increasing the annealing time to 60 and 120 min, the reversion of strain-induced martensite (SIM) and recrystallization of deformed austenite has occurred in the entire microstructure. It was found that with increasing the back-annealing duration, the intensity of Rotated Cube {001}<110> (shear texture) and Cube {001}<100> (recrystallization texture) components was decreased and increased, respectively, due to the occurrence of recrystallization in the microstructure. The hardness, yield strength, and tensile strength of the 900-10 sheet were respectively 1.9 (264 HV vs. 142 HV), 2.4 (527 MPa vs. 216 MPa), and 1.4 (825 MPa vs. 588 MPa) times higher than those of the solution-treated steel owing to the refinement of the austenite grains as well as the presence of deformed γ in the non-surface regions. An obvious recovery of work-hardening rate (WHR) was observed in the second stage of the back-annealed sheets owing to the formation of SIMs and deformation twins during tensile testing. The slope of the WHR curve in the second stage was different for the back-annealed samples at different holding times. With increasing the back-annealing time, the failure mode changed from shear ductile to fully ductile.