Breaking the Paradox of Material Properties through Composition Design and Microstructure Regulation by Professor Yonghao Zhao

NTU MSE Seminar Hosted by Associate Professor Andrew Clive Grimsdale

Abstract

The rapid development of modern industries requires materials to have multiple excellent properties at the same time, but many excellent properties of materials are difficult to coexist, such as the strength and plasticity, strength and conductivity/thermal stability of metals, energy density and power density of battery materials, thermal conductivity and conductivity of thermoelectric materials, coercivity and magnetization of magnetic materials, breakdown strength and polarization strength of dielectric materials, coercive electric field strength and polarization strength of ferroelectric and ferromagnetic materials, damping factor and elastic modulus of damping materials, catalytic activity and catalytic point number of catalytic materials, etc. Various toughening schemes (second phase nano precipitation toughening, twinning deformation toughening, reducing dislocation density toughening, introducing multi-scale grain distribution toughening, etc.) are proposed to address the scientific challenge of mutual exclusion of nano metal strength and plasticity. New concepts of "macroscopic design of material microstructure" and "directional construction of fractal structure" are also introduced to address the difficulty of coexisting strength and conductivity/thermal stability. For high entropy alloys, the strengthening and deformation mechanisms of single-phase FeCoNiCrMn, FeCoNiMoV, and two-phase FeCoNiAlCr high entropy alloys are revealed. High-temperature work hardening mechanism and creep mechanism of Ni₂Co₁Fe₁Mo_0.2V_0.5 medium entropy alloy is shown. High strength and toughness of Ni₂CoFeV medium entropy alloy is achieved through multi-level ordered phases. 

Biography


Professor Yonghao Zhao
Dean of School of Materials Science and Engineering 
Hohai University

Dr. Yonghao Zhao received his Ph.D. from Institute of Metal Research, Chinese Academy of Sciences, China in 2001. He did his postdoctoral research in German Max Planck Institute for Metal Research and Los Alamos National Lab from 2001 to 2007. He served as an Assistant Project Scientist at University of California at Davis from 2007 to 2011. He was a professor at Nanjing University of Science and Technology from 2011 to 2023. Dr. Zhao is currently a Professor and Dean of School of Materials Science and Engineering, Hohai University, Changzhou, China. His research interests include nanostructured metals and alloys as well as high-entropy alloys.