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Undercooled solidification of hypoeutectic Ni-3·3 wt-%B alloy has been studied. The microstructure evolution of Ni-3·3 wt-%B alloy indicates that a transition from regular lamellar eutectic to anomalous eutectic exists with increasing undercooling for eutectic transformation. Here, a new model was proposed to describe the cooling curves of undercooled solidification with two-step transformation. Fits of the present model to the cooling curves after different undercoolings show that the predictions of transformed fractions are compatible with the microstructure observation. Furthermore, for hypoeutectic alloy, the size of the primary phase mainly depends on the undercooling for primary solidification, while the fraction of the primary phase mainly depends on the undercooling for eutectic solidification. [ABSTRACT FROM AUTHOR]

By comparing phase fractions upon solidification of Ni-3·3 wt-%B alloy obtained by differential scanning calorimetry (DSC) measurement, microstructure observation and the baseline method, the results show that although as an approximate approach, the baseline method can be used to predict the phase fractions from the cooling curve, and it can reflect the relationship between the transformed fraction, time and temperature simultaneously during solidification, which cannot be obtained from DSC measurement. In addition, the effects of non-constant specific heat and latent heat of phases on the baseline method are discussed and the calibration relationships are deduced. [ABSTRACT FROM AUTHOR]

A simple method was proposed to calculate the essential parameters correlated with the critical nucleation frequency of undercooled metals and alloy melt. Numerical results show that the calculation accuracy from this method can be improved using the experimental data either with high undercooling or with low undercooling range (the difference of undercoolings between two solidification events). The calculations of the interfacial energy for high undercooling of silver and of the catalytic factor f(h) for high undercooling of Al, Cu and Al-30 wt-%Cu alloy indicate that the results are consistent with the experimental measurements and with the results of Jian's model [Metall. Trans. A, 2001, 32A, 391-395]. In addition, by analysing the differential scanning calorimetry data of pure Sn subjected to different cooling rates, similar values of catalytic factor f(θ) are obtained. This further indicates the validity of the current method. [ABSTRACT FROM AUTHOR]

Assuming constant rates for nucleation and growth and neglecting thermal gradient in the melt, an analytical approach to describe the undercooled solidification was proposed in terms of ja(x) function. This approach was adopted to study the solidification of undercooled Ni-B alloy. With increasing melt undercooling, good model fits to recalescences arising from the solidification of the primary and eutectic phases were obtained. The fitting results are consistent with the structure evolution upon solidification. [ABSTRACT FROM AUTHOR]