Modeling of the Kinetics of Strain‐Induced Martensite Transformation and the Transformation‐Induced Plasticity Effect in a Lean‐Alloyed Metastable Austenitic Stainless Steel

Abstract

This article investigates the influence of temperature and strain on second‐phase transformation strengthening and the resulting mechanical properties in a lean AISI 301LN austenitic stainless steel within a temperature range of −60 to 180 °C. The volume fraction of martensite evolved is determined using nondestructive magnetic Ferritescope measurements that are adjusted by using a calibration factor of 1.7, which is established using the saturation magnetization measurements, X‐ray, and neutron diffraction measurements. The kinetics of strain‐induced martensite transformation (SIMT) as a function of strain and temperature is accurately described by a set of modified constitutive Boltzmann sigmoidal equations at temperatures below 75 °C. For this steel, the Md (30/50) temperature is determined as 61 °C. The absolute Md temperature is established as ≈109 °C, and no athermal transformation to martensite is observed upon cooling to −270 °C using cryogenic neutron diffraction facilities. Extended JMAK analysis of the transformation is used to shed light on the mechanism of martensitic transformation. It is found that the transformation‐induced plasticity (TRIP) effect due to SIMT is at a maximum at 75 °C, which is the maximum elongation temperature (MET) and calculations are performed regarding alloy development which will reduce the MET to room temperature.

Modeling the Tensile Strain Hardening Behavior of a Metastable AISI 301LN Austenitic Stainless Steel Pre-strained in Compression

“…The results of the Ferritescope readings were adjusted to true values of percentage α′martensite by the established calibration curves using a combination of Vibrating Sample Magnetization (VSM) measurements, X-ray, and neutron diffraction analyses. A calibration factor of 1.62 (derived using compressive deformation), [16] and a calibration factor of 1.70 (derived using tensile deformation), [17] were found to be accurate to convert Ferritescope measurements to actual percentage of martensite content. A calibration factor of 1.70 (derived using tensile deformation) was found to be in good agreement with what was reported in the literature [18,19] and was used to convert Ferritescope measurements to arrive at the true α′martensite content during interrupted tensile testing.…”

Effect of element segregation on deformation mechanisms of nano/ultrafine-grained 304 stainless steel

“…This region corresponds to the white circles marked on the schematic in Figure 12(c,d). Higher M d30 value indicated a decrease in the stability of austenite and an increase in the kinetics of the strain-induced martensite transformation [28,52]. Thus, the martensitic transformation occurred preferentially in the Spot 1 region during plastic deformation.…”