Please use this identifier to cite or link to this item: https://doi.org/10.1016/j.jmst.2021.09.049
Title: Effect of a weak magnetic field on ductile–brittle transition in micro-cutting of single-crystal calcium fluoride
Authors: Guo, Y
Lee, YJ 
Zhang, Y 
Sorkin, A 
Manzhos, S 
Wang, H 
Issue Date: 10-Jun-2022
Publisher: Elsevier BV
Citation: Guo, Y, Lee, YJ, Zhang, Y, Sorkin, A, Manzhos, S, Wang, H (2022-06-10). Effect of a weak magnetic field on ductile–brittle transition in micro-cutting of single-crystal calcium fluoride. Journal of Materials Science and Technology 112 : 96-113. ScholarBank@NUS Repository. https://doi.org/10.1016/j.jmst.2021.09.049
Abstract: Magneto-plasticity occurs when a weak magnetic field alters material plasticity and offers a viable solution to enhance ductile-mode cutting of brittle materials. This study demonstrates the susceptibility of non-magnetic single-crystal calcium fluoride (CaF2) to the magneto-plastic effect. The influence of magneto-plasticity on CaF2 was confirmed in micro-deformation tests under a weak magnetic field of 20 mT. The surface pile-up effect was weakened by 10–15 nm along with an enlarged plastic zone and suppressed crack propagation under the influence of the magnetic field. Micro-cutting tests along different crystal orientations on the (111) plane of CaF2 revealed an increase in the ductile–brittle transition of the machined surface with the aid of magneto-plasticity where the largest increase in ductile–brittle transition occurred along the [112¯] orientation from 512 nm to a range of 664–806 nm. Meanwhile, the subsurface damage layer was concurrently thinner under magnetic influence. An anisotropic influence of the magnetic field relative to the single-crystal orientation and the cutting direction was also observed. An analytical model was derived to determine an orientation factor M that successfully describes the anisotropy while considering the single-crystal dislocation behaviour, material fracture toughness, and the orientation of the magnetic field. Previously suggested theoretical mechanism of magneto-plasticity via formation of non-singlet electronic states in defected configurations was confirmed with density functional theory calculations. The successful findings on the influence of a weak magnetic field on plasticity present an opportunity for the adoption of magnetic-assisted micro-cutting of non-magnetic materials.
Source Title: Journal of Materials Science and Technology
URI: https://scholarbank.nus.edu.sg/handle/10635/233898
ISSN: 1005-0302
DOI: 10.1016/j.jmst.2021.09.049
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