Bulk metallic glasses (BMGs) are a broad and relatively young materials class in modern alloys. Featured by amorphous atomic structures, BMGs exhibit superior mechanical and physical properties and have broad applications in high-tech industries such as energy, communication and aerospace. However, BMGs are thermodynamically metastable. At temperatures approaching glass transition temperature, Tg, aging or crystallization can happen, leading to the loss of their unique properties. Therefore, the applications of BMGs are limited to temperatures below their Tg. Some metallic glasses with Tg > 1000 K have been developed, but their narrow supercooled liquid region, ΔT (the temperature window between Tg and crystallization temperature Tx) and marginal glass forming ability (GFA) prohibits practical shaping of the alloys, hence makes them useless for most applications. A requirement for a practical BMG that can be used at temperatures exceeding 1000 K has to be a high Tg, a wide ΔT, and a decent GFA.
LIU Yanhui’s group from the Institute of Physics of the Chinese Academy of Sciences and their collaborators, devised a combinatorial method based on the concept of materials genome engineering. The method, featured by efficiency, non-destructiveness, and extendibility, enables rapid discovery of glass forming alloys within a vast compositional space. They designed an iridium/nickel/tantalum/boron alloy system, and identified high temperature BMGs via their combinatorial method. The BMGs exhibit a Tg up to 1162 K, high resistance to crystallization with a ΔT of 136 K, wider than that of most existing BMGs, and high strength at high temperature, 3.7 GPa at 1000 K. Their GFA is characterized by a critical casting thickness of 3 mm, suggesting that small scale components for applications at high temperature or in harsh environments can be readily obtained by thermal plastic forming. The discovery process of the high temperature BMGs represents a paradigm shift in the development of practical BMGs as it allows to simultaneously optimize many properties required for a BMG to be of commercial use. The study was published in Nature.
