Yu Zou

Emerging thin film technology

Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario, Canada

Email: mse.zou@utoronto.ca

Biography

PROFESSIONAL APPOINTMENTS

University of Toronto, Toronto, ON, Canada                         

Assistant Professor in Materials Science & Engineering (MSE)    January 2018 – Present

•    Principal Investigator in the Laboratory for Extreme Mechanics & Additive Manufacturing

•  Non-budgetary cross-appointment in Mechanical & Industrial Engineering July 2018 – Present

Massachusetts Institute of Technology (MIT), Cambridge, MA, USA

SNSF Postdoctoral Fellow in Mechanical Engineering    June 2016 – December 2017

•    Advisor: A. John Hart, Mechanosythesis Group, Laboratory for Manufacturing & Productivity

EDUCATION

Swiss Federal Institute of Technology Zurich (ETH Zurich), Zurich, Switzerland

Dr. Sc. (Ph.D.) in Materials Science    March 2016

•    Supervisor: Ralph Spolenak, Laboratory for Nanometallurgy

•    Dissertation: “Probing small-scale plasticity: from simple ionic crystals to complex intermetallic phases”

Kyoto University, Kyoto, Japan        August 2014 – January 2015

JSPS visiting PhD student in Mechanical Engineering    

•    Host supervisor: Takayuki Kitamura, Laboratory for Materials and Fracture Mechanics

McGill University, Montreal, QC, Canada

M.Eng. (thesis based) in Materials Engineering    June 2010

•    Supervisors: Jerzy A. Szpunar and Stephen Yue, Laboratory for Microstructure and Texture

Beihang University, Beijing, China

B.Eng. in Materials Science and Engineering    July 2007

•    Advisor: Hua-Ming Wang, Laboratory for Laser Materials Processing and Manufacturing

Abstract for Presentation

Probing small-scale fracture and plasticity in quasicrystals and high-entropy alloys 

In the first part of the presentation, we show that typically brittle quasicrystals can exhibit remarkable ductility of over 50% strains and high strengths of ∼4.5 GPa at room temperature and sub-micrometer scales. In contrast to the generally accepted dominant deformation mechanism in quasicrystals—dislocation climb, our observation suggests that dislocation glide may govern plasticity under high-stress and low-temperature conditions. The ability to plastically deform quasicrystals at room temperature should lead to an improved understanding of their deformation and fracture mechanism.

In the second part of the presentation, we present that the fracture properties of high-entropy alloys (HEAs). Most refractory high-entropy alloys (HEAs) are brittle and suffer from limited formability at ambient temperature. Here, using in situ micro-cantilever tests, we show that the fracture toughness of a bi-crystal HEA, Nb25Mo25Ta25W25, is one order of magnitude lower than that of single crystalline ones.

References

(1)  M. Haché, C. Cheng, and Y. Zou* (Invited Review) “Nanostructured high-entropy materials” Journal of Materials Research 34.20 (2020)

(2)  Y. Xiao, R. Kozak, M. Haché, W. Steurer, R. Spolenak, J. M. Wheeler, Y. Zou* “Micro-compression studies of face-centered cubic and body-centered cubic high-entropy alloys: size-dependent strength, strain rate sensitivity, and activation volumes” Materials Science & Engineering A (2020)

(3) B Zhu, S Alavi, C Cheng, H Sun, H Zhao, K Su Kim, J Mostaghimi, Y Zou* “Fast and High‐Throughput Synthesis of Medium‐and High‐Entropy Alloys using Radio Frequency Inductively Coupled Plasma” Advanced Engineering Materials, 2001116, (2020)

(4) Y. Xiao, Y. Zou, A. S. Sologubenko, R. Spolenak, J. M. Wheeler* “Size-dependent strengthening in multi-principal element, face-centered cubic alloys” Materials and Design (2020)

(5) Y. Xiao, Y Zou, H. Ma, A. S. Sologubenko, X. Maeder, R. Spolenak, and J. M. Wheeler. "Nanostructured NbMoTaW high entropy alloy thin films: High strength and enhanced fracture toughness." Scripta Materialia 168 (2019)

(6) Y. Zou* “Nanomechanical studies of high-entropy alloys” (Invited Review) Journal of Materials Research 33.19 (2018): 3035-3054.

(7) Y. Zou*, J. Wheeler, H. Ma, P. Okle, R. Spolenak “Nanocrystalline high entropy alloys: A new paradigm in high temperature strength and stability” Nano Letters, (2017)

(8) Y. Zou*, P. Okle, H. Yu, T. Sumigawa, T. Kitamura, S. Maiti, W. Steurer, R. Spolenak, “Fracture properties of a refractory high-entropy alloy: In situ micro-cantilever and atom probe tomography studies” Scripta Materialia, 128 (2017)

(9) Y. Zou*, P. Kuczera, A. Sologubenko, T. Sumigawa, T. Kitamura, W. Steurer, R. Spolenak “Superior room-temperature ductility of typically brittle quasicrystals at small sizes” Nature Communications 7, (2016).

(10) Y. Zou, P. Kuczera, W. Steurer, R. Spolenak “Disappearance of plastic anisotropy in decagonal quasicrystals at small scales and room temperature” Extreme Mechanical Letters, 8 (2016)

(11) Y. Zou, J. Wheeler, A. Sologubenko, P. Kuczera, W. Steurer, J. Michler, R. Spolenak “Bridging room-temperature and high-temperature plasticity in decagonal Al-Ni-Co quasicrystals by micro-thermomechanical testing” Philosophical Magazine (2016), 1-23. (12) Y. Zou, H. Ma, R. Spolenak “Ultrastrong, ductile and stable high-entropy alloys at small scales” Nature Communications 6 (2015).

(13) Y. Zou, S. Maiti, W. Steurer, R. Spolenak, “Size-dependent plasticity in an Nb25Mo25Ta25W25 refractory high-entropy alloy” Acta Materialia 65 (2014)