Bulk metallic glasses are a new, fascinating class of materials with special properties such as a low melting temperature, high hardness and scratch resistance, and very high elasticity. They can be formed like plastics at comparatively low temperature and pressed into complex shapes. Compared to their crystalline alloy counterparts, they usually show a higher strength, hardness and a higher elastic strain while the Young's modulus is lower, which makes them excellent spring materials. Precious metals-based bulk metallic glasses were introduced at the 2007 Santa Fe Symposium® by B. Lohwongwatana. To make their way into industrial applications, their properties relevant for jewelry were investigated in a public-funded research project in collaboration with partners from industry. A new casting method was developed in order to exploit their near net-shape formability. Hardness, wear resistance and tarnishing in different atmospheres were investigated. With an as-cast hardness of around 360HV, a liquidus temperature below 400°C (752°F) and the as-cast color of premium white-gold alloys, the gold-based bulk metallic glass alloy has attractive qualities for jewelry applications.

Author(s): Dr. Ulrich E. Klotz