Coupling of Homogeneous and Heterogeneous Melting Kinetics in Polycrystallines

Melting kinetics of polycrystallines is analyzed on the basis of a new model which explicitly couples homogeneous and heterogeneous melting mechanisms. The distinct feature of this approach lies in its ability to evaluate not only grain-size-distribution effects on the overall melting kinetics but also competitions between the two melting mechanisms. For the first time, we reveal the three-part structure of temperature-time-transformation diagrams for melting of polycrystallines, through which it is possible to determine a critical temperature across which the dominant melting mechanism switches. The critical temperature increases as the mean-grain-diameter decreases following a negative power-law.