The magneto-plastic effect on dislocation activity has been under heavy investigation through the mid 1900s but has yet to be explored in the micro-scale until now. It is even more unique with the use of a weak magnetic field on paramagnetic and diamagnetic materials as opposed to the hazardous use of strong magnetic fields on ferromagnetic work materials. The notion put forth was that the magnetic field restructures the spin orientation and state of defects that results in dislocation depinning. We approached this phenomenon by performing density functional theory (DFT) calculations of the defect formation energies, ground-state spin states, and singlet-triplet energy gaps to evaluate the candidacy of the material to be affected by the magneto-plastic effect [1]. The identification of potential defects with low singlet-triplet energy gaps, which indicate the propensity for external field-assisted conversion, progressed on to demonstrate the impact of the magnetic field on lowering the stress fields and consequently delaying the ductile–brittle transition during micro-deformation of brittle materials [2]. Molecular dynamics (MD) simulations further reveal that the magnetic field improves dislocation-dominant lateral and tangential plastic flow during micro-scratching [3]. This phenomenon not only manifests in brittle ionic crystals but also diamagnetic metal, copper, where we identified secondary anisotropic influences of the magnetic field lines relative to the crystallographic orientation that affect micro-cutting forces [4] and machined subsurface damage [5]. The concept of electromagnetism affecting the machinability of brittle materials is also currently being adapted through electro-plastic effects on the deformability of single-crystal brittle materials [6].

Publications

[1] Y. Guo, et al., Effect of a weak magnetic field on ductile–brittle transition in micro-cutting of single-crystal calcium fluoride, Journal of Materials Science & Technology, 112 (2022) 96–113.

[2] Y. Guo, et al., Mechanism in scratching of calcium fluoride with magneto-plasticity, International Journal of Mechanical Sciences, 263 (2024) 108768.

[3] Y. Guo, et al., Predictive modelling for enhanced scratching of brittle ceramics with magneto-plasticity, International Journal of Mechanical Sciences, 249 (2023) 108272.

[4] Y. Guo, et al., Magneto-plasticity in micro-cutting of single-crystal copper, Journal of Materials Science & Technology, 124 (2022) 121–134.

[5] Y. Guo and H. Wang, Magnetic field dependent machinability in ultra-precision machining of single-crystal copper, in: 9th International Conference of Asian Society for Precision Engineering and Nanotechnology (Aspen), Singapore, 2022.

[6] J. Zhan, Y. Guo, H. Wang, Electro-plastic effect on the indentation of calcium fluoride, International Journal of Mechanical Sciences, 261 (2024) 108693.

Acknowledgements

This research is proudly supported by the Singapore MOE Academic Research Fund Tier 2 Grant (MOE-T2EP50220-0010).