A few details of the austenite to martensite phase transformation in 304 stainless steel powders under mechanical processing

This work investigates the phase transformation kinetics of 304 stainless steel powders submitted to mechanical processing by ball milling. The mechanical treatment induces an austenite to martensite phase transformation at rates dependent on the frequency of collisions between the milling tools. The degree of phase transformation was estimated by quantitative X-ray diffraction as well as by saturation magnetization measurements, the martensite phase being ferromagnetic. A mathematical description of the phase transformation kinetics was developed by taking into account the intrinsic statistical character of the mechanical processing methods. This allowed us to obtain information on events occurring during individual collisions.