Control of austenite to martensite transformation through equal channel angular pressing aided by thermodynamic calculations

The martensite start temperature and driving force were calculated for the austenite to martensite transformation of a dual-phase bainitic ferrite–austenite steel at room temperature. The mechanical energy was estimated during the first and the second pass of equal channel angular pressing (ECAP). The applied mechanical energy during the first pass is not enough to induce the austenite to martensite transformation. However, the mechanical energy during the second pass can provide the required energy for the martensite formation. Microstructural observations by transmission electron microscopy and scanning electron microscopy of as-received and ECAPed samples confirm the formation of martensite during the second pass.