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ANNUAL ISSUE

EARLY CAREER SCHOLARS IN MATERIALS SCIENCE

Nanostructured high-entropy materials Michel J.R. Haché1, Changjun Cheng1, Yu Zou1,a) 1

Department of Materials Science and Engineering, University of Toronto, Toronto, ON M5S 3E4, Canada Address all correspondence to this author. e-mail: [email protected] This paper has been selected as an Invited Feature Paper. a)

Received: 9 November 2019; accepted: 16 January 2020

In the past decade, the emergence of high-entropy alloys (HEAs) and other high-entropy materials (HEMs) has brought about new opportunities in the development of novel materials for high-performance applications. In combining solid-solution (SS) strengthening with grain-boundary strengthening, new material systems— nanostructured or nanocrystalline (NC) HEAs or HEMs—have been developed, showing superior combined mechanical and functional properties compared with conventional alloys, HEAs, and NC metals. This article reviews the processing methods, materials, mechanical properties, thermal stability, and functional properties of various nanostructured HEMs, particularly NC HEAs. With such new nanostructures and alloy compositions, many interesting phenomena and properties of such NC HEAs have been unveiled, for example, extraordinary microstructural and mechanical thermal stability. As more HEAs or HEMs are being developed, a new avenue of research is to be exploited. The article concludes with perspectives about future directions in this field.

Yu Zou

Yu Zou is a Dean’s Spark Assistant Professor in the Department of Materials Science and Engineering at the University of Toronto. Before joining the University of Toronto in 2018, he was a postdoctoral fellow in the Department of Mechanical Engineering at Massachusetts Institute of Technology (MIT), working on laserbased metal additive manufacturing with Prof. A. John Hart. He received his Doctor of Sciences in Materials from ETH Zurich in 2016 with Prof. Ralph Spolenak. His doctoral thesis focused on small-scale plasticity of ionic crystals, HEAs, and quasicrystals. He was also a JSPS visiting scholar at Kyoto University in 2014, working on in situ nanomechanical testing with Prof. Takayuki Kitamura. He received his master’s and bachelor’s degrees from McGill University and Beihang University, respectively, all in materials science and engineering. At McGill, he worked on cold sprayed metallic coatings with Profs. Jerzy Szpunar and Stephen Yue. He currently directs the Laboratory for Extreme Mechanics & Additive Manufacturing (LEMAM) at the University of Toronto. His group seeks to develop novel experimental, simulation, and analytical methods to explore new metallic materials and advance fields of vital importance to society, including the aerospace, biomedical, and energy sectors. Currently, his group has four primary emphases: (i) new nanostructure alloys, (ii) multiscale mechanical testing, (iii) multimetal additive manufacturing, and (iv) high-throughput experimentation. At the University of Toronto, he has been awarded Connaught New Re