Microstructual evolution of a medium carbon advanced high strength steel heat-treated by quenching-partitioning process

摘要

The recently developed "quenching and partitioning"(Q&P) and "quenching-partitioning-tempering"heat treatment are both novel processing technologies, which are aim to achieve advanced high strength steels with good combination of high strength and ductility. Containing certain amount of ductile austenite phase is a key characteristic of the Q&P steel, and austenite phase is being enriched with carbon during the partitioning treatment. However, the microstructural evolution of the Q&P steel during the heat treatment is rather complicated. In present work, evolution of microstructure in medium carbon steel containing Cr, Mo, and Nb has been studied in detail during the Q&P process. The microstructural evolution of the steel was investigated in terms of X-ray diffraction, scanning electron microscope, and transmission electron microscope. The present study shows that good combination of high tensile strength and relatively high ductility of a microalloyed carbon steel have been attained by quenching-partitioning-tempering process. The experimental results show that the sample partition-tempered for 30 s exhibits best comprehensive mechanical properties, which result from the integrated effect of carbide precipitation, conservation of certain amount of retained austenite and softening of the martensite matrix during the partition-tempering process.

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