Effect of Cooling Practice on the Mechanical Properties of Medium-Manganese Aluminum-Alloyed Steels after Intercritical Annealing Quench and Partition Treatment

Abstract

This study reports the effect of different cooling practices after hot rolling on the<br/>microstructure and mechanical properties of intercritically annealed quench and partitioned low-carbon medium-manganese aluminum-alloyed steel. The outcomes show that the tensile strength and uniform elongation of medium-<br/>manganese steels can be improved by manipulating the cooling cycle after<br/>hot rolling. The starting microstructure, obtained after hot rolling and cooling,<br/>influences the fraction of austenite formed at the end of intercritical annealing,<br/>thereby impacting the fraction of martensite produced at the interrupted<br/>quenching step. The results illustrate that during intercritical annealing austenite tends to nucleate at a higher temperature from a ferritic microstructure compared to a microstructure consisting of mainly bainite or a mixture of ferrite, martensite, cementite, and retained austenite. Partition temperature of 400 °C facilitates the partition of carbon from martensite to austenite while partition temperature of 450 °C supports the formation of high carbon secondary martensite.