Prof. Shiteng Zhao
[Beihang University]

Talk Title: Probing Extreme Materials Science by High-Power-Pulsed Laser

Time:  10:00-11:00, Jun. 29, 2021

Place: Conference room 410, HPSTAR (Shanghai)

       Tencent Conference Meeting ID: 131 482 498

Host: Hongliang Dong/Bin Chen

Abstract:

Pulsed lasers with power on the order of terawatts, once deposited on a target surface, will launch a strong stress pulse that propagates into the material. Owing to the ultrashort duration of the laser pulses, unprecedented extreme conditions which combine high pressures (and/or shear stresses), strain rates and temperatures can be generated in materials, yielding a yet unexplored regime of materials under extreme conditions. During the talk, I will first summarize our efforts on laser shock compression of four covalently bonded materials, namely, silicon, germanium, boron carbide and silicon carbide (SiC). These materials are known to have high Peierls-Nabarro stress and negative Clapeyron slope. The profile of the shock waves was measured by a velocity interferometer system for any reflectors (VISAR). The shock deformation microstructure has been revealed by high-resolution scanning/transmission electron microscopy and all the materials exhibit shock-induced amorphization. This discovery indicates shock-induced amorphization as a generalized deformation mechanism under strong shock condition. Laser shock experiments can also be extended to the tensile regime when the compressive wave was reflected by the free surface. The tensile wave, once exceeds the ultimate tensile strength of the materials, will lead to a catastrophic failure. Our recent efforts on dynamic tensile fracture of CoNiCr-based high entropy alloy (HEA) will be discussed.  These materials show strong resistance to shear localization under impact loading, which is mainly due to HEA's low stacking fault energy and therefore easy propensity to undergo twinning. Our results suggest that CoNiCr-based HEA may have good ballistic protection application.

Biography of the Speaker:

Shiteng Zhao

2021.05 to present, Professor,

School of Materials Science and Engineering

Beihang University, szhao@buaa.edu.cn

WORKING EXPERIENCE

Postdoc, Department of Materials Science and Engineering,

University of California, Berkeley

Research Associate, National Center for Electron Microscopy,

Lawrence Berkeley National Laboratory

2018 to 2021, (Advisor: Prof. Andrew Minor)

EDUCATION

University of California, San Diego, USA

2017, Ph.D.  Materials Science (Advisor: Prof. Marc A. Meyers),

RWTH Aachen University, Germany

2013, Msc.  Metallurgical Engineering (Advisor: Prof. Günter Gottstein)

University of Science and Technology Beijing, China

2010, BS.   Materials Science & Engineering

Research Interests

1)        Materials under extreme conditions (high stress-state, high strain rate);

2)        Multiscale microstructural design of advanced alloys;

3)        Advanced electron microscopy.

Selected Publications

1. S. Zhao, B. Kad, B. A. Remington, C.E. Wehrenberg, J. Lasalvia, K. Beuler, M.A. Meyers, Directional amorphization of boron carbide subjected to laser shock compression. Proc. Nat. Acad. Sci. U.S.A. 2016; 113;12088-12093.

2. S. Zhao, B. Kad, C.E. Wehrenberg, B.A. Remington, E.N. Hahn, K.L. More, M.A. Meyers, Generating Gradient Germanium Nanostructures by Shock-induced Amorphization and Crystallization. Proc. Nat. Acad. Sci. U.S.A. 2017, 114, 9791-9796.

3. S. Zhao, E. N. Hahn, B. Kad, B. A. Remington, C.E. Wehrenberg, E. M. Bringa, M. A. Meyers, Amorphization and Nanocrystallization of silicon under shock compression, Acta Materialia 2016 103:519-533.

4. S. Zhao*, R. Flanagan, E.N. Hahn, B. Kad, B.A. Remington, C.E. Wehrenberg, R. Cauble, K. More, M.A. Meyers*, Shock-induced amorphization in silicon carbide. Acta Materialia, 2018, 158, 206-213.

5. S. Zhao, R. Zhang, Y. Chong, X. Li, A, Abu-Odeh, E. Rothchild, D. Chrzan, M. Asta, J.W. Morris Jr, A. Minor, Defects reconfiguration in a Ti-Al alloy via electroplasticity, Nature Materials, 2021, 20 (4), 468-472.

6. S. Zhao, Z. Li, C. Zhu, W. Yang, Z. Zhang, D. Armstrong, P. Grant, R. Ritchie, M. Meyers, Amorphization in extreme deformation of the CrMnFeCoNi high-entropy alloy, Science Advance, 2021, 7(2), eabb6063.

7. R. Zhang†, S. Zhao†, J. Ding, C. Ophus, M. Asta, R. Ritchie, A.M. Minor, Short-range order and its impact on the CrCoNi medium-entropy alloy, Nature, 2020, 581, 283-287. (Contributed equally)

8. S. Zhao, B. Li, B. Remington, C. Wehrenberg, H. Park, E. Hahn, M. A. Meyers, Directional amorphization of covalently bonded solids: a generalized deformation mechanism in extreme loading, Materials Today, 2021.

9. R. Zhang†, S. Zhao†, C. Ophus, T. Pckin, Y. Deng, S.J. Vachhani, B. Ozdol, R. Traylor, K. Bustillo, M. Poschmann, J.W. Morris Jr, D.C. Chrzan, M. Asta, A. M. Minor, Direct imaging of short-range order and its impact on deformation in Ti-6Al, Science Advances, 2019, 5, eaax2799. (Contributed equally)