CaAl-based bulk metallic glasses with high thermal stability

Abstract

We report that binary Ca–Al alloys can be readily cast into amorphous rods of 1 mm in diameter. Upon further alloying to depress the liquidus temperature, the amorphous rod diameter is increased to 3 mm. The high glass transition temperature Tg∼210 °C and crystallization onset temperature Tonset∼240 °C or higher observed are attributed to the covalent bonding trend noted in Ca–Al alloys that exhibit complex network structures. Along with a high microhardness value of 200–235 DPH (diamond pyramid hardness) and low mass densities of 2 gm/cm3, these thermally stable light-metal alloys are recognized as potential structural amorphous metals.