Effect of Partition Temperature on Microstructure and Mechanical Properties of Cold-Rolled Medium-Manganese Steel

Abstract

The influence of different heat-treatment conditions on the microstructure evolution and mechanical properties of cold-rolled Fe–7.69Mn–2.76Al–0.12C (wt%) steel is investigated using various techniques, including scanning electron microscopy, transmission electron microscopy (TEM), and X-ray diffraction. In the results, it is shown that the stability of austenite is significantly affected by different partitioning temperatures. It is found that factors such as dislocation density, temperature, and grain size collectively influence partitioning behavior. In the observations, it is revealed that when the partitioning temperature is raised from 120 to 180 °C, the dislocation density of the face centered cubic phase within the test steel decreases from 10.38 × 10¹⁶ to 7.67 × 10¹⁶ m⁻². Additionally, within specimens exhibiting higher dislocation densities, carbon element diffusion is more uniform. During the experiment, the poor stability of the austenite is found to be susceptible to stress-inducing the phase of the martensitic transformation, and the type of the martensite transformation affects the deformation process and the performance of submission behavior. In the observations under TEM, a phenomenon where variations in dislocation density within individual austenite grains may lead to differing stability across grain regions is revealed, thereby triggering localized martensitic phase transformations.