Anisotropic brittle-ductile transition of monocrystalline sapphire during orthogonal cutting and nanoindentation experiments

Maas Philipp, Mizumoto Yuta, Yasuhiro Kakinuma, Min Sangkee

Research output: Contribution to journalArticle


Single-crystal sapphire is utilized as a high-performance engineering material, especially in extreme and harsh environments. However, due to its extreme hardness and brittleness, the machinability of sapphire is still a challenge. By means of nanoindentation and plunge-cut experiments, the anisotropic brittle-ductile transition of the prismatic M-plane and rhombohedral R-plane is examined by analyzing crack morphologies and the critical depth-of-cut (CDC). The experimental results of the nanoindentation tests are correlated to the plunge-cut experiment. Both the prism plane and the rhombohedral crystal plane exhibit a two-fold symmetry of ductility with various crack patterns along the machined grooves. The direction-dependent plasticity of the hexagonal sapphire crystal is mainly connected to a twinning process accompanied by slip dislocation.

Original languageEnglish
Pages (from-to)157-171
Number of pages15
JournalNami Jishu yu Jingmi Gongcheng/Nanotechnology and Precision Engineering
Issue number3
Publication statusPublished - 2018 Sep 1



  • Anisotropy
  • Brittle-ductile transition
  • Orthogonal cutting
  • Sapphire

ASJC Scopus subject areas

  • Instrumentation
  • Mechanical Engineering
  • Industrial and Manufacturing Engineering

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