Alloying and heat treatment effect on a medium-Mn steel

Abstract

A base 10Mn-0.15C-2Al (in wt. %) steel was sequentially alloyed with Mo, B, V, and Cu to identify the effects of both alloying addition and heat treatment on the microstructure and properties of the steel. The volume fraction and stability of the austenite as influenced by alloy content and intercritical annealing temperature produced the greatest effect on room temperature quasi-static tensile and Charpy V-notch (CVN) impact properties. When CVN testing was performed at -40 °C the impact properties were independent of austenite and produced an average of 74 ± 4 J apart from the Base alloy that had exceptionally low toughness of 28 J at -40 °C. The austenite fractions were shown to be controlled by the thermodynamic stability of the austenite as calculated through the Ghosh-Olson martensite model. Finally, the effect of microstructure on toughness metrics was considered and it was found that increased retained austenite did not always provide increased toughness.