A novel approach based on the quantitative phase field model was proposed to calculate the interface mobility and applied to the α/β interface of a ternary Ti-6Al-4V alloy.Phase field simulations indicate that the higher interface mobility leads to the faster transformation rate,but only a unique value of interface mobility matches the diffusion equation under the diffusion-controlled condition.By comparing the transformation kinetics from phase field simulations with that from classical diffusion equation,the interface mobility at different temperatures can be obtained.The results show that the calculated interface mobility increases with increasing temperature and accords with Arrhenius equation very well.
The glass formation was intensively studied for Fe-based alloys. Parameters defining kinetics and thermodynamic behavior of crystallization were calculated using calorimetric measurements and physical properties of constituent elements. It is found that the critical cooling rate Rc estimated by combining kinetic and thermodynamic parameters highly correlates with measured Rc found in literatures with correlation coefficient R2=0.944, and alloy compositions with high melting enthalpy AHm can easily form glass even without high undercooling and high value of the ,β-parameter of Tumbull's theory, revealing that the glass formation in this group of alloys is mostly controlled by growth limitation. This combination of kinetic and thermodynamic parameters can be used to determine alloy composition with good glass forming ability in Fe-based alloys just using physical properties of alloying elements and calorimetric measurements.
The phase-field model of a liquid-to-solid transition was constructed where the model parameters were linked quantitatively to the interfacial properties, and the variation of nucleation barrier height in undercooled metallic melts with respect to undercooling was studied respectively based on two kinds of forms of local free energy density. The calculation results show that, with the increase of undercooling, the critical nucleus does not show bulk properties, and the nucleation barrier height decreases gradually and deviates more and more from that predicted by the classical nucleation theory in both cases. The physical spinodal occurs for a specific form of the local free energy density, where the nucleation barrier height vanishes when the undercooling reaches a critical value and the reduced nucleation barrier height can be expressed by a function of the ratio of undercooling to critical undercooling.