Effects of strain-induced martensite and its reversion on the magnetic properties of AISI 201 austenitic stainless steel

Strain-induced martensite (SIM) and its reversion in a cold-rolled AISI 201 austenitic stainless steel was studied by means of magnetic properties, light optical (LOM) and scanning electron (SEM) microscopy, electron backscatter diffraction (EBSD), texture measurements, and Vickers microhardness testing. According to Thermo-calc (c) predictions, the BCC phase (residual delta-ferrite and SIM) is expected to be stable until 600 degrees C. The current material was cold rolled up to 60% thickness reduction and submitted to both isothermal and stepwise annealing up to 800 degrees C. Magnetic measurements were taken during annealing (in situ) of the samples and also for their post mortem conditions. The Curie temperatures (T-c) of residual delta-ferrite and SIM have similar values between 550 and 600 degrees C. Besides T-c., the focused magnetic parameters were saturation magnetization (M-s), remanent magnetization (M-R), and coercive field (H-c). SIM reversion was found to occur in the range of 600-700 degrees C in good agreement with Thermo-calc (c) predictions. The microstructures of the material, annealed at 600 and 700 degrees C for 1 h, were investigated via EBSD. Microtexture measurements for these samples revealed that the texture components were mainly those found for the 60% cold rolled material. This is an evidence that the SIM reversion occurred by an athermal mechanism. (C) 2016 Elsevier B.V. All rights reserved.