Crystallization Kinetics and Fragility of Al-Based Amorphous Alloy

Abstract

Crystallization among amorphous alloy is a crucial study since it generally affects it properties, which may detrimental or beneficial, depending in the intended application of the materials. Controlling crystallization is crucial for obtaining the desired properties. The crystallization study was performed using differential scanning calorimeter (DSC). Samples were heated at heating rate between 20 and 40 K·min-1. Structural evolution during crystallization was studied under X-ray diffraction (XRD). Apparent activation energy for each temperature characteristics was determined using Kissinger’s equation. Local Avrami exponent was investigated using modified Johnson-Mehl-Avrami-Kolgomorov equation. Liquid fragility, which indicates the strength of the glass formation, was predicted using temperature characteristics instead of its viscosity. It was found that upon crystallization both as-cast samples crystallize to cubic-Al, Al2CuMg and Al2Cu and Al3Ni. Alloy with composition of (Al75Cu17Mg8)95Ni5 shows superior activation energy at every temperature characteristics than alloy with composition of Al75Cu10Mg8Ni7. Local Avrami exponent and local activation energy for (Al75Cu17Mg8)95Ni5 show high values at the beginning and at the end of crystallization process. From liquid fragility, it was predicted that the samples are stronger glass former than previous studied Al-amorphous alloys.