Hafnium based metallic glasses with high density and high glass-forming ability

Metallic glasses (MGs) are advanced alloys possessing an amorphous structure and a host of properties (e.g., theoretical-limit-approaching strength) far superior to conventional crystalline metals/alloys. Hafnium based MGs (HBMGs) have the additional advantage of high density, desirable for critical applications such as kinetic energy penetrators. HBMGs have still limited glass-forming ability (GFA), with a critical casting diameter/thickness (Dc) <= 10 mm, beyond which crystallization will occur. We report our discovery of two HBMGs, Hf40Zr9Cu31Ni8Al12 and Hf43Zr4Cu31.25Ni9.75Al12 possessing a Dc of 18 mm which nearly doubles the current record and enables notably bigger products and easier manufacturing/processing of HBMGs. Both alloys possess a density above 10.2 g/cm(3), higher than most MGs based on other elements (e.g., Fe, Cu). They also stand out from most other MGs with a high T-rg > 0.61, high gamma-parameter > 0.42 and high atomic packing efficiency > 0.8. We also report their thermal and mechanical properties and discuss the factors that may have contributed to their exceptional GFA. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Metallic glasses, especially Hafnium based MGs, have superior properties to conventional crystalline metals/alloys, with HBMGs having the additional advantage of high density. However, their glass-forming ability is limited. Our discovery of two HBMGs with a critical casting diameter significantly higher than the current record allows for the production of bigger products and easier manufacturing/processing.