Effect of a weak magnetic field on ductile-brittle transition in micro-cutting of single-crystal calcium fluoride  

作　　者：Yunfa Guo Yan Jin Lee Yu Zhang Anastassia Sorkin Sergei Manzhos Hao Wang 

机构地区：[1]Department of Mechanical Engineering,National University of Singapore,9 Engineering Drive 1,Singapore 117575,Singapore [2]School of Materials and Chemical Technology,Tokyo Institute of Technology,Ookayama 2-12-1,Meguro-ku,Tokyo 152-8552,Japan

出　　处：《Journal of Materials Science & Technology》2022年第17期96-113,共18页材料科学技术（英文版）

基　　金：supported by the Ministry of Education,Singapore,under its Academic Research Funds(Grant Nos.:MOE-T2EP50120-0010,MOE-T2EP50220-0010);the funding from the Ministère des Relations Internationales et de la Francophonie du Québec,Coopération Québec-Singapour,with which this work was partially supported。

摘　　要：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(CaF_(2))to the magneto-plastic effect.The influence of magneto-plasticity on CaF_(2) 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 CaF_(2) 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.

关 键 词：Magneto-plasticity Weak magnetic field Brittle material Ductile-brittle transition MICRO-CUTTING 

分 类 号：TQ132.32[化学工程—无机化工]