Stemming from the 3rd generation of Advanced High Strength Steels (AHSS), the Q&P steels present an above-average balance of strength and ductility than similar compositions processed using traditional heat treatments. These properties arise from the transformation induced plasticity (TRIP) effect that the retained austenite endures. The retained austenite is stabilized at room temperature due to the carbon partitioning from the supersaturated martensite. These mechanisms have already been studied at great length for carbon steels, but for Q&P stainless steels not as thoroughly. This work aims to expand the knowledge in this area, specifically the relationship between microstructure and mechanical behaviour.

Stainless steel samples were heat treated via Q&P with varying quenching temperatures, partitioning temperatures and partitioning times. Sub size tensile specimens were machined out of the samples and tested. Tensile mechanical properties and strain hardening behaviour were analysed. The microstructures of these samples were also characterized before and after tensile testing. Individual microconstituents were identified, and their size and volume fraction were measured.

The experimental results were used to adjust a theoretical model that describes the work hardening behaviour of this specific material, Q&P treated martensitic stainless steel. An analysis of the resulting model is performed to establish the most influential parameters in this relationship. A general recipe for microstructural design to improve the strain hardening behaviour of the Q&P treated stainless steels is proposed.