Development of Rare-Earth Element Based High Entropy Bulk Metallic Glasses

摘要

High entropy alloys (HEAs) are a relatively new class of metallic materials. HEAs lead to high mixing entropy and the formation of a simple solid solution rather than intermediate phases. This might be explained by the fact that the configurational entropy outweighs the enthalpy of formation of intermetallic compounds. Meanwhile, bulk metallic glasses (BMGs) are representative of multicomponent systems which have (1) low thermodynamic driving force for crystallization, and (2) low atomic mobility associated with viscosity. Recently, it was reported that high entropy BMG (HE-BMG) can be fabricated by combining the concepts of both BMGs and HEAs. These alloys usually consist of at least five constituent elements with an equi-atomic or near equi-atomic ratio. In the present study, we focused on the development of new rare-earth element (RE)-based HE-BMGs by changing both the number and the kinds of the RE elements in the RE-Al-TM (transition metal) BMGs. We carefully considered the following factors for alloy design: 1) heavy RE based BMGs exhibit a relatively high glass-forming ability and high thermal stability; 2) the elements of the RE group have many common properties, with only very small differences in solubility and complex formation, which makes it difficult to separate or even distinguish among them. We evaluated the glass-forming ability and unique properties of the newly developed RE-based HE-BMGs, and compared their properties with those of other conventional multi-component alloys. This report will provide a novel alloy design strategy for HE-BMGs that possess the characteristics of both HEA and BMG.