Effect of annealing temperature on the microstructure, tensile properties, and fracture behavior of cold-rolled high-Mn light-weight steels

Abstract

The effects of the annealing temperature on the microstructure and tensile properties of cold-rolled light-weight steels are investigated using two Fe-30Mn-xAl-0.9C alloys that contain different A1 content. The initial alloy microstructure is composed of a single austenite or a mixture of austenite and ferrite depending on the nominal aluminum content. For the alloy with 9 wt% A1 content, the recrystallization and grain growth of austenite occurrs depending on the annealing temperature. However, for the alloy with 11 wt% A1 content, the β-Mn phase is observed after annealing for 10 min at 550~800 °C. The β-Mn transformation kinetics is the fastest at 700°C. The formation of the β-Mn phase has a detrimental effect on the ductility, and this leads to significant decreases in the total elongation. The same alloy also forms K-carbide and DO3 ordering at 550~900°C. The investigated alloys exhibit a fully recrystallized microstructure after annealing at 900°C for 10 min, which results in a high total elongation of 25-55% with a high tensile strength of 900-1170 MPa).