Glass Forming Ability of Bulk Amorphous Materials in Cu-Zr-Ag Ternary Alloy Systems

Abstract

The glass forming ability (GFA) of the Cu-Zr-Ag alloy system was investigated on the basis of the thermal stability, and the structural, thermodynamic and kinetic properties of the material. We changed the concentration of the alloys, as we departed from the Cu58Zr42 composition and produced three different eutectic points in the Cu-Zr-Ag ternary system, in accordance with the results published in the respective literature. We produced various test pieces of Cu-Zr-Ag amorphous alloys with different Ag contents (0-70%), by casting the material into wedge-shaped copper moulds. In such ternary alloy system there is only a limited concentration range where amorphous materials can be produced: in the event that the Ag content of the material exceeds 35 at%, no amorphous material structure will develop. In our experiment the maximum temperature range of the supercooled liquid region (ΔTx) was 75 K. The calculated four GFA parameter values are not in perfect harmony and fail to point out the optimal composition available; however, based on γ and the reciprocal value of ω, the best compositions from the GFA aspect are Cu42.5Zr37.5Ag20 and Cu40Zr37.5Ag22.5. The decrease of the maximum thickness of the bulk metallic glasses is influenced more by the oxygen content than the composition changes within the Cu-Zr-Ag system.