37th MSL Lecture (Prof. Yanbin Wang)
| Date/Time | 2017/05/29 14:00-15:30 |
|---|---|
| Place | 1F Meeting Room, Building R3 |
| Organizer | Laboratory for Materials and Structures |
| Contact | Nori Nishiyama (Wakai-Nishiyama Lab.) email: nishiyama.n.ae@m.titech.ac.jp; tel: 045-924-5337 |
Subject & Detail
Speaker： Prof. Yanbin Wang
(GSECARS, The University of Chicago, USA )
Title： "High-pressure and temperature plastic deformation of polycrystalline diamonds, with prospects of studying other superhard materials"
Abstract:
A series of deformation experiments was conducted on several selected sintered polycrystalline diamonds (PCD) using the deformation DIA (D-DIA) apparatus at Sector 13 (GSECARS) of the Advanced Photon Source (APS). The samples were well-sintered bulk PCDs sintered with either Co (from Sumitomo and Sandvik Hyperion) or Si (from Sandvik Hyperion) as binding material. Samples were deformed at ~7 GPa and 1273 K, under an essentially identical strain rate of 1.5x10^(-5) s^(-1). Under such conditions, PCDs are expected to deform by dislocation creep. The ability to plastically deform the hardest known material to strains up to ~20% is primarily due to the development of nano-polycrystalline diamond (NPD), which has mechanical properties superior to PCDs with micron-sized grains. NPD deformation pistons allowed proper transmission of differential stress from the D-DIA to the samples.
We also deformed NPD samples to compare their mechanical properties with PCD. NPD is brittle at 7 GPa and 1273 K. It
cracks and does not deform plastically. At 9 GPa and 1473 K, however, NPD does deform plastically and exhibits a remarkably high strength, more than twice that of Co-based PCD. NPD deformation mechanism appears very different from that in PCD. Prospects of studying other superhard materials in the D-DIA will be discussed.
