Effect of thermomechanical processing in the intercritical region on hardenability of austenite of a dual-phase steel

Steels slabs containing different percentages of C, Mn, and Cr were intercritically heat treated and rolled at 780 and 790 degreesC; they were then quenched to produce dual-phase microstructure in order to study the martensitic hardenability of austenite present in them. It was found that rolling of the two-phase (alpha + gamma) microstructure elongated austenite particles and also reduced the martensitic hardenability of austenite particles, probably because the rolling increased the alpha/gamma interfacial area, thus promoting the formation of ferrite during cooling. The martensite particles obtained in the rolled material were also elongated or "fibered" in the rolling direction. It was observed that the thermomechanical processing of a two-phase (alpha + gamma) mixture has the detrimental effect of increasing the quenching power needed to yield a specific amount of martensite.