Tin-modified gold-based bulk metallic glasses

Tin was selected as a modifying element in low-gold-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 Au50Sn6Cu26Si18 with 18.6-karat gold and a diameter of 1 mm possessed a lower glass transition temperature (Tg) 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 Au50Sn6Cu26Si18 was from 108 to 109 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 Tg but not so obvious above Tg. The low viscosity of this BMG Au50Sn6Cu26Si18 at around 102°C, which is very close to the boiling temperature of water (100°C), rendered easy thermal–mechanical deformation in a boiling water-bath by hand-pressing and tweezers-bending. Such a deformation capability in boiling water is beneficial to the further applications in various fields.