Lee Hsun Lecture Series

Topic: Bulk Metallic Glasses

Speaker: Dr. Jan Schroers, Yale University

Abstract:

Bulk metallic glass (BMG) formers are multicomponent alloys that vitrify with remarkable ease during solidification. Technological interest in these materials has been generated by their unique properties, which often surpass those of conventional structural materials. The metastable nature of BMGs, however, has imposed a barrier to broad commercial adoption, especially where the processing requirements of these alloys conflict with conventional metal processing methods. Research on the crystallization of BMG formers has uncovered novel processing opportunities using thermoplastic forming (TPF), which utilizes the dramatic softening exhibited by a BMG as it approaches its glass transition temperature. Fabrication processes based on TPF decouple the rapid cooling required to form a glass from the forming step, mitigate the effects of heterogeneities on crystallization, and overcome geometrical limitations associated with casting. This talk introduces such techniques that are unique among metals. Within TPF, BMGs can be considered high strength material that can be processed like (thermo) plastics, whereby previously mutually exclusive attributes of materials -processability and performance – can be combined.

In most potential applications, BMGs are limited by their fracture toughness and not by their strength. I will discuss recent progress in determine fracture toughness, and how it is affected by processing.

I will then discuss the limited commercial adaptation of BMGs to date due to the inability to effectively develop BMGs with required combinations of properties. Novel alloy development strategies will be introduced that will allow us to identify bulk metallic glass forming compositions faster. Combinatorial sputtering paired with high-throughput characterization is one such method, which will be introduced and discussed on how it can be expanded to multi-parameter optimization process to develop BMG alloys that could be widely adapted by industry.