B. Gun

The Prediction of Glass-Forming Compositions in Metallic Systems - The Development of New Bulk Metallic Glasses

A novel methodology of predicting specific compositions for glass forming alloys based on elemental cluster selection, liquidus lines, atomic packing efficiency and ab initio calculations is presented and discussed. The proposed composition selection model has lead to the discovery of a number of novel, soon to be reported Mg, Cu, Zn and Ag-based bulk metallic glasses. The proposed model may also be used to explain high glass forming ability and physical properties of known BMG compositions and to pin-point new or superior BMG compositions in existing glass forming systems. Further, the aforementioned model shows strong correlations between proposed elemental clusters, glass forming ability and BMG ductility. This model has also shown applicable adaptation to known ceramic oxide glass forming systems.

The Production and Elevated Temperature Properties of Ca65Mg15Zn20 Bulk Metallic Glass

Ca65Mg15Zn20 bulk metallic glass samples of dimensions 3.15 × 7 × 125 mm were prepared using an inverted low-pressure die-casting technique. It was found that charge temperature, and injection pressure were important parameters for controlling the length, porosity and degree of crystallinity in the as-cast samples. A processing map was generated illustrating the optimum casting temperature and pressure range for generating the highest quality castings. These samples were ground into tensile samples in compliance with ASTM E8-04 and deformed in the supercooled liquid (SCL) region (105 to 135 °C) at constant strain rates from 10-3 to 10-4 s-1. Reported are the effects of these parameters on the deformation behaviour of the Ca65Mg15Zn20 BMG.