Effects of Second Phase Particles on Migration of α/γ Interface during Isothermal α to γ Transformation

The effects of insoluble particles on migration of ferrite (alpha)/austenite (gamma) interface during isothermal alpha to gamma transformation at 1 133 K have been studied by means of a model experiment using diffusion couple method and a multi-phase field simulation. It was found that the insoluble particles, ZrO2 or TiO2 particles, could retard the migration of alpha/gamma interface. And the tendency that the retarding effect becomes stronger with higher volume fraction of TiO2 particle was observed. However, the retarding effect of ZrO2 on alpha/gamma interface is not as strong as that on delta-ferrite (delta)/austenite (gamma) interface during peritectic transformation. The phase field simulation indicates that this reduction of retarding effect originates from the appearance of carbon pile-up in gamma phase, which is also caused by the existence of particles. In addition, it is shown that the difference between sigma(alpha/p) and sigma(gamma/p), the interfacial energy between matrix (alpha or gamma) and particles, strongly affects the migration velocity of alpha/gamma interface.