Tin-modified gold-based bulk metallic glasses

Abstract

Tin was selected as a modifying element in lowgold-content (50 at.%) bulk metallic glasses (BMGs) aiming at developing alloys with cost-effective performance. New gold-based Au-Sn-Cu-Si alloys were fabricated by injection-casting into a copper mold. The as-cast BMG Au 50 Sn 6 Cu 26 Si 18 with 18.6-karat gold and a diameter of 1 mm possessed a lower glass transition temperature (T g ) of 82°C (355 K), a lower liquid temperature of 330°C (603 K), and a super-cooled liquid region of 31°C. The viscosity range of this BMG Au 50 Sn 6 Cu 26 Si 18 was from 10 8 to 10 9 Pa s measured at a low applied stress of 13 kPa. To compare the viscosity with different applied stresses, its viscosity clearly increased with applied stress below T g but not so obvious above T g . The low viscosity of this BMG Au 50 Sn 6 Cu 26 Si 18 at around 102°C, which is very close to the boiling temperature of water (100°C), rendered easy thermal-mechanical deformation in a boiling waterbath by hand-pressing and tweezers-bending. Such a deformation capability in boiling water is beneficial to the further applications in various fields.

A Gold-Based Bulk-Solidifying Amorphous Alloy for Jewelry — Comparison with a Palladium-Based Amorphous Alloy

“…However for a 18 karat Au-base alloy the value of 360 HV is very high and confirms the interest of such a BMG. These results are in agreement with values reported in the literature [8][9][10][11][12][13][14].…”

“…The binary gold silicon eutectic composition was the first alloy found to exhibit metallic glass formation by Klement and co-workers in 1960 [7]. Then gold based bulk metallic glass alloys were developed with a weight content comparable to 18 karat gold [8][9][10][11][12][13][14][15]. The alloys show a low liquidus temperature, large supercooled liquid region, large maximum casting thickness, and good processability for both casting and thermo-plastic processing.…”

“…Schroers et al [8][9] reported a multicomponent gold base BMG alloy (Au 76.5 -Cu 13.5 -Si 3.6 -Ag 4.7 -Pd 1.9 (wt%)) as an alternative for jewelry applications with a critical casting thickness of several millimeters. Wang et al [14] investigated a Tin modified gold-based BMG. The Au 50 Sn 6 Cu 26 Si 18 is attractive since it exhibits a low glass transition temperature (82°C) and also a low liquid temperature (330°C).…”