Experimental quantitative observation of magnetic field accelerated γ-α phase transformation in an Fe-based alloy

The magnetic field, along with temperature, significantly affects the mechanism of phase transformation, requiring detailed quantitative analysis. In this study, the influence of a magnetic field on the γ-α (austenite-ferrite) isokinetic phase transformation process of an Fe-1wt% Cu alloy was quantitatively analyzed through kinetics analysis by in-situ magnetization measurement. The kinetic calculation results demonstrate that the magnetic field accelerates the γ-α phase transformation, leading to shorter transformation time, increased transformation rate, and grain refinement. Quantitative analysis of Avrami exponent, driving force, nucleation barrier and activation energy directly indicates that the magnetic field induces a shift from a site saturation nucleation mode to a continuous nucleation mode, increases the driving force of phase transformation, and reduces the nucleation barriers and activation energy, ultimately resulting in a higher nucleation rate, faster phase transformation rate, and more uniform and finer grain structure. Simultaneously, the magnetic field alters the impingement mode during isokinetic phase transformation, shifting it from anisotropic growth impingement to randomly dispersed nuclei impingement.