Microstructure and mechanical property relationship in a high strength high-Al low-Si hot-dip galvanized steel under quenching and partitioning process

Abstract

We elucidate here profound effects of quenching and partitioning process on the microstructure and mechanical properties of high strength hot-dip galvanized steel with high Al and low Si content. The results indicated that partitioning time significantly affected the morphology and volume fraction of retained austenite (RA). A change in austenite from film-like to blocky structure with the increase of partitioning time was observed. Increasing partitioning time also increased the volume percentage of RA up to 8.95 vol.%. Using annealing temperature of 967 °C, quenching temperature of 267 °C, partitioning temperature and time of 460 °C and 90 s respectively, the experimental steel exhibited excellent mechanical properties with tensile strength of 728 MPa, total elongation of 30% and the product of strength and ductility was 21,840 MPa%. The variation in strength, elongation, strain-hardening behavior and phase transformation mechanism with different partitioning time is discussed in relation to the RA stability.