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37th MSL Lecture (Prof. Yanbin Wang)

Date/Time 2017/05/29 14:00-15:30
Place 1F Meeting Room, Building R3
OrganizerLaboratory for Materials and Structures
ContactNori Nishiyama (Wakai-Nishiyama Lab.)
email: nishiyama.n.ae@m.titech.ac.jp; tel: 045-924-5337

Subject & Detail

37th MSL Lecture

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.

 

Wakai-Nishiyama Lab.

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