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

• Published in: Journal of alloys and compounds 2021-11, Vol.882, p.160896, Article 160896
• Main Authors: Saini, Jaskaran Singh, Miska, John P., Lei, Fuqiong, AuYeung, Nicholas, Xu, Donghua
• Format: Article
• Language: English
• Subjects: Amorphous materials; Amorphous structure; Crystallization; Density; Diameters; Differential scanning calorimetry; Glass formation; Hafnium; Kinetic energy; Mechanical properties; Metallic glass; Metallic glasses; Quenching; Solidification; Thermodynamic properties
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.160896

•We report two Hf-based bulk metallic glasses with exceptional glass-forming ability.•Their critical casting diameter is 18 mm, nearly doubling current record (Hf-alloys).•The new alloys have a density>10.2 g/cm3, higher than most bulk metallic glasses.•The new alloys have a high Trg>0.61 and high γ-parameter>0.42.•The new alloys have a high atomic packing efficiency exceeding 0.8. 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/cm3, higher than most MGs based on other elements (e.g., Fe, Cu). They also stand out from most other MGs with a high Trg>0.61, high γ-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.