Processing-Structure-Property Relationships for Bulk Metallic Glasses

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• Professor Jay Kruzic
• Tuesday 04 February 2025, 15:00-16:00
• Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS.

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Bulk metallic glasses (BMGs) are alloys with exceptionally high strength, and they can range from very tough to brittle depending on their structural state. However, quantifying their processing-structure-property relationships has been a long unresolved challenge because their amorphous glassy structures lack the familiar long-range order and lattice defects of crystalline solids. In this work, we examine how local hardness variations within BMG microstructures strongly affect the fracture behavior and how the glassy microstructures can be altered by thermomechanical treatments such as cold deformation and cryogenic cycling to enhance the fracture toughness. Moreover, we have demonstrated using nanobeam electron diffraction and fluctuation electron microscopy that the hardness heterogeneities are controlled by the size and volume fraction of nanoscale FCC -like medium-range order (MRO) clusters. We have then utilized atom probe tomography and a novel cluster analysis approach to observe and quantify the three-dimensional distribution, chemical composition, volume fraction, and morphology of nanoscale MRO clusters and we have proposed a model of ductile phase softening whereby relatively soft FCC -like MRO clusters sit in a matrix of harder icosahedral dominated ordering. Additionally, we have been exploring the prospects for controlling the glassy structure and mechanical properties of BMGs using additive manufacturing by laser powder bed fusion (LPBF). LPBF was used to produce dense Zr59.3Cu28.8Nb1.5Al10.4 BMG samples from two different starting powders and fully amorphous samples were achieved within a large range of laser power and scanning speed combinations. Strength and hardness generally increased with increasing laser energy density while the relaxation enthalpy, ductility, and fracture toughness decreased. When the LPBF energy density was raised above _{30-33 J/mm3, high relative density was maintained along with devitrification and embrittlement. Low energy densities below} 20 J/mm3 had low relative density

Jay Kruzic joined UNSW Sydney as a Professor of Mechanical and Manufacturing Engineering in 2016, and he held the position of Deputy Head of School from 2017 – 2023. He was educated in the United States, receiving a B.S. degree in Materials Science and Engineering from the University of Illinois, Urbana-Champaign, in 1996 followed by M.S. and Ph.D. degrees in Materials Science and Mineral Engineering from the University of California, Berkeley, in 1998 and 2001, respectively. Following a period of three years as a postdoctoral fellow at Lawrence Berkeley National Laboratory he joined Oregon State University as an Assistant Professor in 2004. After being promoted to Associate Professor in 2008, he became Professor in 2014 in the School of Mechanical, Industrial, and Manufacturing Engineering at Oregon State University. His research focuses on the mechanical behaviour of a wide range of engineering materials (metals, ceramics, intermetallics, composites), biomaterials, and biological tissues, with emphasis on the mechanisms of fracture, fatigue, and deformation.

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