Crystallization kinetics of Mg65Cu25Nd10 amorphous alloy

Amorphous Mg-based alloy Mg65Cu25Nd10 was prepared by melt-spinning. The kinetics of crystallization of the alloy was investigated by DSC using various heating rates, and its crystallization process and microstructure were confirmed by TEM, X-ray and electron diffraction. The changeable activation enthalpy Ea with crystalline fraction α was given by an isoconversional method, and the average value of Ea was 150 ± 10 kJ/mol. What is more important, it is shown that this process cannot be described by the JMA model but the two-parameter empirical Sestak–Berggren equation gives a more quantitative description. It was established that the crystallization of Mg65Cu25Nd10 alloy is a multi-step mechanism and can be described by the Sestak–Berggren model with the kinetic parameters as follows: m = 0.59, n = 1.42, A = 6.35 × 1014. It was found that the crystallization process of melt-spun Mg65Cu25Nd10 ribbons consists of three steps. The first crystallization reaction at about 453 K is connected with the formation of Mg2Cu nanocrystalline phase, followed by formation of a coarser grained α-Mg crystalline phase (483–500 K) corresponding to a second crystallization reaction. At higher temperatures a third exothermic effect (at about 593 K) can be detected and the stable Mg2Cu, α-Mg and Cu5Nd phases are present.