Introduction of sulfur into an eutectic of the Zr-Ti-Ni-Cu system: Alloy development and characterization of the (Zr50Ti16.6Ni18.3Cu15)100-xSx bulk metallic glasses

Abstract

The influence of sulfur additions to the quaternary Zr50Ti16.6Ni18.3Cu15 alloy was investigated in terms of glass forming ability, thermophysical properties and mechanical properties in high purity alloy variants as well as in industrial grade alloys. In the latter case, oxygen was found to cause only a minor reduction of glass forming ability whilst retaining good mechanical properties. Conventional powder diffraction as well as synchrotron high energy diffraction revealed that the addition of sulfur changes the primary phase that forms during casting and the glass forming properties can be enhanced by adding a specifically tailored amount of sulfur to the alloy. The resulting alloys can be tailored to either possess a large glass forming ability with a critical casting size of 6 mm with 2–3 at% S or a large supercooled liquid region for sulfur amounts above 6 at%. Mechanical properties show a compressive strength of 1.6 GPa paired with high ductility, that shows in a compressive strain to failure ≥ 5.8 %, as well as conditional fracture toughness values of KQ ≥ 79 MPa√m in both the high purity and industrial grade variants, despite severe oxygen contamination. This indicates superior resistance against embrittlement compared to other Zr-based bulk metallic glasses.