Work

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

Year: 2018

Type: article

Abstract: 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.

Source: Nanotechnology and Precision Engineering

DOI: 10.1016/j.npe.2018.09.005

Authors: Philipp Maas, Yuta Mizumoto, Yasuhiro Kakinuma, Sangkee Min

Institutions: University of Wisconsin–Madison, Keio University

Language: English

Topic: Advanced Surface Polishing Techniques

Subfield: Biomedical Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: diamond

Funder: Japan Society for the Promotion of Science

Award: Challenge to highly-efficient ultra-precision machining for next-generation optical element by assisting optical resonance