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Abstract: Considering nucleation, growth and impingement, a numerical model was proposed to describe the transformation kinetics of rapid solidification in bulk undercooled Fe–B hypereutectic alloy. Applying heat balance and solute conservation, the changes of temperature and composition of residual liquid are proved to be not only dependent of time, but also associated with the solidified fraction during the transformation. Accordingly, the driving force for non-equilibrium solidification, as well as the determined nucleation and growth rates, decreases with the process of transformation. On this basis, the primary grain size distribution formed in this process can be predicted with the combination of classical Kolmogorov–Johnson–Mehl–Avrami (KJMA) equation and a probability statistic analysis. Good agreement between the model prediction and experimental results has shown the validity of the proposed model. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, thermodynamic and kinetic calculations were combined to study the glass forming ability of Cu–Zr binary system. Applying thermodynamic association model, the primarily crystallized phase and its corresponding driving force can be determined firstly. Then, the whole Time–Temperature–Transformation (TTT) diagrams basing on homogeneous and heterogeneous nucleation modes have been constructed quantitatively. As for the former case, the critical cooling rate is underestimated by about three orders of magnitude in comparison with the experimental observation. As for the latter case adopting suitable values of catalytic factor f(θ) and potential nuclei N 1, the predictions agree well with the experimental results, and moreover, the nose temperature of TTT diagram is upper-shifted. This has been discussed using a competition of the atomic mobility and the reduced nucleation barrier, as well as its further effect on the nucleation and growth process. [Copyright &y& Elsevier]

Abstract: The effect of microstructure on the anisotropy and the coercivity in HDDR Nd–Fe–B magnet has been investigated by putting forward a theoretical anisotropy model influenced simultaneously by both the structure defect and the exchange coupling interaction. The results showed that the coercivity is greatly influenced by both the defect thickness, r 0, and the anisotropy constant, K 1(0), at grain surface. Coercivity is determined by the pinning mechanism when K 1(0)≤0.4K 1 and r 0 <4nm or K 1(0)>0.4K 1. However, it is controlled by the nucleation mechanism when K 1(0)≤0.4K 1 and r 0 >8nm. For all values of K 1(0), the coercivity first increases, reaches the maximum and then decreases with increasing r 0, and its maximum value decreases with increasing K 1(0). The maximum coercivity is 1102KA/m while K 1(0)=0 and r 0 is close to the thickness of domain wall (∼4nm), which is consistent with experimental results given by other authors. [Copyright &y& Elsevier]