Influence of the phase transformation behaviour on the microstructure and mechanical properties of a 4.5 wt.-% Mn Q&P steel

Abstract

“Quenching and Partitioning” (Q&P) steels have a microstructure consisting of a tempered martensitic matrix with austenite islands, which can be stabilized to room temperature due to the C partitioning from martensite to the remaining austenite. This heat-treatment is a novel approach for producing ultra-high strength and good formable steels. In the present work the impact of the Q&P processing parameters on the phase transformation behavior and mechanical properties of a 4.5 wt.% Mn steel was investigated. Using dilatometry the influence of the quenching temperature (TQ) on the amount of martensite and the kinetics of the bainitic transformation was thoroughly studied. The microstructure was characterized by means of light optical and scanning electron microscopy. The amount of retained austenite was determined using the saturation magnetization measurement. In order to obtain the mechanical properties hardness measurements according to Vickers were performed. Furthermore, using tensile tests the Q&P concept was compared to the Quenching and Tempering (Q&T) process in terms of strength-ductility performance.