A new microstructural design is proposed to develop a strong and ductile quenching and partitioning (Q&P) steel with low yield ratio. This steel has a heterogeneous dual phase microstructure which is developed by varying austenite thermal stability through Mn segregation. The heterogeneous microstructure contains large austenite grains which contribute to the low yield strength. The ultra-high tensile strength and good ductility are ascribed to the enhanced strain hardening behaviour resulted from the continuous transformation-induced plasticity (TRIP) effect. The present microstructural design enables a conventional medium Mn steel with high tensile strength, good ductility and low yield ratio, which promises easy forming and potential applications in automotive industries.
This paper is part of a Thematic Issue on Medium Manganese Steels.
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