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 (α)/austenite (γ) interface during isothermal α to γ transformation at 1133 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 α/γ 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 α/γ interface is not as strong as that on δ–ferrite (δ)/austenite (γ) interface during peritectic transformation. The phase field simulation indicates that this reduction of retarding effect originates from the appearance of carbon pile-up in γ phase, which is also caused by the existence of particles. In addition, it is shown that the difference between σα/p and σγ/p, the interfacial energy between matrix (α or γ) and particles, strongly affects the migration velocity of α/γ interface