Jaime J. Kruzic, Professor
School of Mechanical and Manufacturing Engineering
University of New South Wales (UNSW Sydney), Australia

Abstract
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 structure-property relationships has been an unresolved challenge because their amorphous glassy structures lack the long-range order and crystalline defects that typically define the structure-property relationships for crystalline alloys. 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 FCC-like medium-range order (MRO) clusters. Additionally, 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, while micropillar compression testing has revealed how the activation of these clusters into shear transformation zones can be negatively affected by oxygen impurities which in turn lower the fracture toughness. Finally, the prospects for controlling the glassy structure and mechanical properties of BMGs using additive manufacturing by laser powder bed fusion will be discussed.

Speaker Biography
Jay Kruzic joined UNSW Sydney as a Professor of Mechanical and Manufacturing Engineering in 2016, and he was appointed Deputy Head of School in 2017. 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.