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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: The effects of convection diffusion, gravity, temperature gradient on the liquid-phase separation were discussed in this work. Originally, collision and congregation were mainly controlled by Brown motion of droplets, which was strong influenced by the initial density of droplets in undercooled melt. As the droplets radius increased, the velocities of Stokes and Marangoni motion increased continuously. Compared to Marangoni migration, Stokes motion was easier influenced by the number and radius of droplets. Moreover, Stokes motion plays a dominant role in the collision and congregation process when a critical radius rd was far exceeded. [Copyright &y& Elsevier]

Abstract: Assume that the intergranular phase (IP) existing between adjacent grains is a weak magnetic phase, and could weaken or interrupt the intergrain exchange-coupling interaction (IECI). Using our proposed cubic-grain anisotropy model, we investigate the effects of IP''s thickness d, and its anisotropy constant K 1(0) on the coercivity of nanocrystalline Nd–Fe–B magnet. Calculation results indicate that the coercivity increases with increasing d, but decreases with increasing K 1(0). When d =1.2nm and K 1(0)=0.5K 1 (K 1 is the common anisotropy constant of the bulk Nd–Fe–B material), our calculated results are consistent with available experimental data. [Copyright &y& Elsevier]