Study on technical parameters and suitability of Pt-based metallic glasses for jewellery applications

Jewellery-specific standardized tests as well as bulk metallic glasses (BMG)-specific testing methods were performed on a series of Platinum (Pt)-based BMGs with and without phosphorous, to evaluate their suitability as jewellery items. Their mechanical properties (elasticity, Young’s modulus as well as Yield stress) were determined by three-point beam bending measurements. Hardness, wear and corrosion resistance were tested in comparison to state of the art crystalline Pt-based jewellery alloys. The Pt-BMG alloys exhibit elastic elongation of about 2%. Compared to conventional crystalline Pt-alloys, their fracture strength of ca. 2 GPa and their hardness of ca. 450 HV1 is four and two times higher, respectively. However, the BMG show less abrasion resistance in the pin disc test than the conventional benchmark alloys, due to adhesive wear and micro cracking. Regarding the corrosion resistance in simulated body fluids, the BMG alloys reveal a slightly higher release of metals, while the tarnishing behaviour is comparable to the benchmark alloys. The P-free Pt-BMG alloy showed a pronounced tarnishing during exposure to air at elevated temperature. The outstanding thermoplastic formability, a special feature of amorphous metals that can be crucial for enabling novel and filigree designs, was determined and quantified for all BMG alloys.