Effect of Cryorolling–Annealing and Bake-Hardening on the Microstructure and Mechanical Properties of AISI 301LN Grade Austenitic Stainless Steel

Abstract

Steel is a valuable material for automotive and structural applications. Due to global warming, vehicle manufacturers are trying to lower the weight of the automobiles without hampering the safety. Austenitic stainless steel has recently gained attention for its superior strength and ductility along with lower maintenance costs. AISI 301LN grade austenitic stainless steel produces a high percentage of strain-induced martensite on cold rolling than other grades of austenitic stainless steel, like AISI 304, AISI 316, and AISI 301, etc. After annealing at elevated temperatures, cold-rolled austenitic stainless steel produces ultra-fine grain structures (~ 0.2–0.5 µm) which improve the yield strength due to the Hall–Petch effect. In the present work, cold rolling was performed at liquid nitrogen (~ 196 °C) temperature, followed by annealing at 700 °C for 20 min ,and finally bake-hardened at 170 °C for 2 h, exhibiting nearly 1000 MPa yield strength, ~ 1200 MPa ultimate tensile strength, and ~ 26% ductility. These demonstrate better mechanical properties (~ 20% improvement in tensile strength) than previously obtained results. The micro-structures and texture of the newly developed advanced steel were examined by TEM, EBSD, and XRD characterization techniques.