The effect of non-equilibrium δ/γ transition on the formation of metastable “dendrite core” in undercooled Fe–Cu alloy

Abstract

The effect of non-equilibrium δ/γ transition on the formation of metastable “dendrite core” in undercooled Fe–Cu alloy was studied. Three kinds of solidified paths were adopted following recalescence, i.e., quenching at recalescence moment, quenching after recalescence plateau and natural cooling. In comparison of the three paths, it was evidenced that the metastable “dendrite core” resulted in the incomplete transition of the primary δ dendrite to γ phase. In combination with the JMA solid-state transition kinetic theory, the formation of “dendrite core” was dominated by volume diffusion controlled-δ/γ transition. Two typical morphologies, i.e., small granules and dendrite trucks in “dendrite cores”, have been detected. It may be attributed to the volume fraction of δ/γ transition.