Crystallization characteristics of the Mg-rich metallic glasses in the Ca-Mg-Zn system

Metallic glasses in the composition range of Ca4Mg72-xZn24+x (x = 0-12, Delta x = 2) were successfully prepared using the melt-spinning technique. The crystallization characteristics of the alloys were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and electrical resistance measurements. All samples show a complex crystallization process with four exothermic events. The phases resulting from each crystallization stage were identified by XRD. The crystallization was initiated at lower temperatures by the precipitation of Mg51Zn20 crystals. Mg-hcp and Ca16.7Mg38.2Zn45.1 (IM1) ternary compound precipitated from the retained amorphous phase during the second crystallization event. After that, Ca1.5Mg55.3Zn43.2 (IM4) ternary compound formed at higher temperatures and the crystallization event terminated via IM4 transforming to Ca2Mg5Zn13 (IM3) before melting. All crystallization reactions were found to be in qualitative agreement with the equilibrium phase diagram. The activation energy for each stage of crystallization was determined from DSC analysis and calculated by Kissinger method. The temperature dependence of electrical resistance shows good consistency with DSC and XRD results. (C) 2012 Elsevier B. V. All rights reserved.