Atomistic Mechanism of Deformation in Metallic Glasses

The Department of Mechanical Engineering & Materials Science presents The Aris and Bessie B. Phillips Lectureship in Theoretical and Applied Mechanics

Dr. Takeshi Egami
Joint Institute for Neutron Sciences, Department of Materials Science and Engineering
Department of Physics and Astronomy, University of Tennessee, Knoxville, TN and Oak Ridge National Laboratory, Oak Ridge, TN

Atomistic Mechanism of Deformation in Metallic Glasses

Metallic glasses are a new family of glasses, made of complex alloys of metallic elements. They look like a regular metal, but their atomic structure is totally amorphous. They have extremely high strength, comparable to best crystalline alloys, and are promising as structural materials. Macroscopically they deform and fail in a similar way as crystalline metallic alloys, by forming shear bands. But upon close look they exhibit a number of unique properties not found in crystalline alloys, because glasses are essentially frozen liquid, and retain some features of behavior as liquid. Elucidation of their behavior has been challenging, because we understand so little about liquid and glass, compared to crystalline materials. At present most theories in materials science and condensed matter physics assume lattice periodicity, whereas in liquid and glass atoms are arranged in a disordered manner. The absence of translational symmetry makes it so difficult to develop sufficiently powerful and sophisticated theory of liquid and glass. Fortunately rapid advances in computational power helped us through model simulation. We discuss how simulation, coupled with advanced x-ray and neutron scattering measurements, helped unravel the solid/liquid duality in the nature of metallic glasses under stress [1-5].

[1] P. Guan, M.-W. Chen and T. Egami, Phys. Rev. Lett., 104, 205701 (2010).
[2] W. Dmowski, T. Iwashita, C.-P. Chuang, J. Almer and T. Egami, Phys. Rev. Lett. 105, 205502 (2010).
[3] T. Iwashita, D. M. Nicholson and T. Egami, Phys. Rev. Lett., 110, 205504 (2013).
[4] Y. Fan, T. Iwashita and T. Egami, Nature Commun. 5, 5083 (2014).
[5] T. Egami, Y. Tong and W. Dmowski, Metals, 6, 22 (2016).

February 3, 2016
9 Hillhouse Avenue
Mason Lab 107
2:30-3:30 P.M.
Reception to follow 3:30 – 4:30 P.M. in Mason Lobby