Fig. 1. Spin conversion of radical pairs under the magnetic field.

Fig. 2. Experimental micro-cutting setup: (a) magnetic field-assisted machining setup using an electromagnet on an ultra-precision machine center; (b) illustration of the varying magnetic field directions relative to the micro-cutting test direction; (c) schematic of the reverse in polarity of the electromagnets.

Fig. 3. Recorded cutting forces plots: (a) varying magnetic field intensity and polarity; (b) varying magnetic field directions during the micro-cutting process; (c) consolidated average cutting force measurements with respect to the magnetic field direction, intensity, and polarity for t0 = 10 μm and υc = 20 mm/min. (NMF: no magnetic field. MF: with magnetic field).

Fig. 4. Consolidated average cutting force measurements (column graph) and percent reduction in cutting force (line + symbol graph) for varying magnetic field orientations (20 mT & N-S) with respect to (a) cutting speed (t0 = 10 μm) and (b) uncut chip thickness (υc = 20 mm/min) on cutting force. (NMF: no magnetic field. MF: with magnetic field).

Fig. 5. Micro-cutting chip morphology under varying magnetic field conditions for t0 = 10 μm and υc = 20 mm/min.

Fig. 6. Chip length and folding thickness for varying magnetic field orientations.

Fig. 7. Comparison of experimental and theoretical relative change of cutting forces and at B=20 mT. For theoretical calculation, and B0 is estimated as 215 mT for copper [29], and the value of proportionality factor kρ is set as 1 [22].

Fig. 8. (a) Schematic of deformation behavior and chip formation during orthogonal cutting. (b) Slip planes and slip directions in (111) single crystal. (c) Magnetic-induced transition in dislocation flow mode and cross-section of chip during chip formation. (d) Formation mechanism of surface folds on the free side of chip at different magnetic conditions.

Fig. 9. Values of orientation factor mO with magnetic field direction for activated slip systems. (mO1 = average values of orientation factor in ($\bar{1}11$)[$0\bar{1}1$] and ($1\bar{1}1$)[$10\bar{1}$] slip systems. mO2 = average values of orientation factor in ($\bar{1}11$)[101] and ($1\bar{1}1$)[011] slip systems.)

Fig. 10. Optical microscopic and AFM imaging of the machined surfaces under varying magnetic field conditions for t0 = 10 μm and υc = 20 mm/min and the observable surface textures: transverse micro-stripes (T1), diagonal folds (T2), crater zone (T3), and “mushroom-like” folds (T4).

Fig. 11. Machined surface profile measurements: top view of the machined surface produced (a) without magnetic field, (b) with a magnetic field (90°), surface roughness profiles along (c) Path 1 (P1), Path 2 (P2), and Path 3 (P3) in the absence and presence of magnetic field (90°).

Fig. 12. Surface roughness measurements under varying magnetic field directions: (a) arithmetic mean height Ra, and (b) average peak-valley Rz.

Fig. 13. Transmission electron microscopic (TEM) analysis of the subsurface produced without magnetic field: (a) cross-sectional side view of the machined subsurface, (b) selected area electron diffraction (SAED) pattern of region A in (a), and (c) high-magnification bright-field image of region B in (a).

Fig. 14. TEM analysis of the subsurface produced with magnetic field: (a) cross-sectional side view of the machined subsurface, (b) SAED patterns of region A in (a), and (c) SAED pattern of region B in (a).

Fig. 15. Cutting-induced microhardness at the magnetic-free condition and varying magnetic field for t0 = 10 μm and υc = 20 mm/min: (a) indentation curves; (b) measured microhardness and elastic modulus.