Temperature induced transformation of metastable austenite in a hypereutectic iron-based rapidly solidified powder

Rapidly solidified powder of a hypereutectic iron-based alloy with the chemical composition of 3% C–3% Cr–12% V (wt.%) was prepared by nitrogen gas atomization. Phase identification of the rapidly solidified particles in the as-atomized state was performed by X-ray analysis and Mössbauer spectrometry. The main phase constituents present in the rapidly solidified particles were found to be metastable austenite and vanadium rich carbide phases of M4C3 type. Magnetic α-phase was identified as a minor constituent. Thermal stability of metastable austenite in the RS particles was analyzed during differential thermal analysis continuous heating experiment and by Mössbauer spectrometry and X-ray diffraction analysis after isothermal exposition at room temperature. The beginning of a fcc (austenite) → bcc (ferrite) + carbide transformation was detected during continuous heating experiment at 612 °C as exothermic reaction. No appreciable changes in the spectral lines after isothermal treatment were observed up to 500 °C. A fcc-to-bcc transformation started after tempering at 500 °C and was completed after tempering at 560 °C.