Abstract:
This study evaluated the microstructural evolution in a medium carbon high silicon steel during one-step, and two-step quench
and partition (Q&P) processes using dilatometry experiments. The two-step Q&P process was carried out using different quench
temperatures ranging from 180 to 260 oC. In the one-step process, Q&P heat treatment samples were held isothermally for ten minutes
after quenching at specified temperatures ranging between 200 and 450oC. The two-step Q&P process yielded a higher fraction of
retained austenite than a one-step Q&P process. During the isothermal hold step, the volume expansion due to carbon partitioning
and austenite decomposition behavior was interpreted by experimentally determined strain values. For the one-step Q&P process,
the austenite decomposition kinetics above and below the Ms temperature differed, as evidenced by the JMAK parameters. The TTT
diagram generated for the one-step Q & P process showed a “swing back” at a temperature of around 355oC.
