Computational thermodynamics to identify Zr-Ti-Ni-Cu-Al alloys with high glass-forming ability

We have used a thermodynamic computational approach to identify the compositions of Zr-Ti-Ni-Cu-Al alloys exhibiting low-lying liquidus surfaces, which tend to favor the formation of bulk metallic glasses. Guided by these calculations, we have identified several series of new Zr-based alloys with excellent glass formability, some of which can be cast into glassy rods up to 14 mm in diameter. These alloys exhibit wide undercooled liquid regions (T-x-T-g) up to 85 K and high Vickers hardness from 550 to 700 kg/mm(2). The best glass-forming alloy is Zr51Ti5Ni10Cu25Al9. The computational thermodynamic approach coupled with the reduced glass transition temperature criterion of Turnbull can rapidly identify regions of alloy composition suitable for experimental tests for glass formation. The glass-forming ability of the alloys we studied can be understood in terms of the relative liquidus temperature in a thermodynamically calculated temperature vs. composition section through a multicomponent phase diagram. It does not follow several other proposed thermodynamic or topological criteria. Our general approach may be extended into a universal too] to identify alloys with good potential to form bulk glasses. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.