Optimized Properties of a Quenching and Partitioning Steel by Quenching at Fine Martensite Start Temperature

Five quenching temperatures were designed to investigate the relationship between volume fraction of retained austenite and microstructure, mechanical properties of a medium carbon quenching and partitioning (Q&P) steel. It is normally accepted that the optimal mechanical property of Q&P steels is obtained by quenching at optimum temperature, which corresponds to the maximum amount of retained austenite. However, the present work clarified that maximum volume fraction of retained austenite in Q&P steels is indeed unrelated to the optimum mechanical property of steels. The microstructure consisting of coarse martensite laths, dispersive bainite and thin retained austenite films was obtained by quenching at fine martensite start temperature (FMs), resulting in the optimum comprehensive mechanical property of Q&P steel with the better elongation at the expense of slightly smaller yield strength and tensile strength.

Automated summary

The study reveals that the optimal mechanical properties of Q&P steels do not necessarily correspond to the highest volume fraction of retained austenite. Quenching at the fine martensite start temperature can achieve a Q&P steel with better elongation at the expense of slightly lower yield strength and tensile strength.