Design of Multi-Principal Element Metallic Glass with Superior Tensile Ductility

Project: Research

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Description

Metallic glasses (MGs) are well known for their superb strength, excellent elastic strain limit, superior thermal-plastic formability and outstanding corrosion resistance. Therefore, they have been considered as an excellent candidate material for structural applications, particularly for micro- and nano-devices. However, the Archilles’ heel of MGs is their lack of tensile ductility at room temperature, which limits their widespread applications even at the small size scale. Over the past years, extensive research efforts have been dedicated to overcoming the tensile brittleness in MGs; nevertheless, as of today, the achieved room-temperature tensile ductility is still limited, with a maximum of 1.6% at a yield strength of 1.6 GPa. In this project, we would like to propose the design of multi-principal element MGs or high entropy MGs (HEMGs) that can overcome the tensile brittleness in conventional MGs. Our preliminary results already showed that the HEMG with the carefully selected composition can attain a tensile ductility of 3% at a yield strength of 2 GPa, outperforming the so-called ductile MGs reported in the literature. Compared to conventional MGs, such as Zr-based MGs that exhibit a well-defined atomic cluster (i.e., icosahedral cluster) as their prototypical short-range order (SRO), the atomic structure of the HEMGs we designed contains a variety of atomic clusters as their SROs, which is seemingly in line with their compositional complexity (i.e., without any base element). Very interestingly, while this unique amorphous structure still yields via the formation of shear bands, it quickly undergoes shear induced ordering as the shear band propagates into the amorphous structure, leading to the self-locking of individual micro-sized shear bands and hence shear band proliferation at the macroscopical scale. As a result, the HEMG exhibits unusual plasticity even under tension. As inspired by this interesting finding, we would like to address the following critical issues if the project could be funded: (1) what is the nature of SROs or even medium range orders (MROs) in our HEMG? (2) what causes shear induced ordering in our HEMG, as opposed to shear induced disordering in conventional MGs? (3) Is there a systematic way that help us identify those MGs which could have a similar deformation mechanism as the HEMG we discovered? In the long run, we envision that our research may stimulate further interest in the design of ductile glasses and spur innovations in the manufacturing of high-quality glasses, which could be valuable to the reindustrialization of Hong Kong. 

Detail(s)

Project number9043523
Grant typeGRF
StatusActive
Effective start/end date1/10/23 → …