On the mechanism of asymmetric ductile–brittle transition in microcutting of (111) CaF2 single crystals

In contrast to forming an amorphous deformed layer, lattice rotation induced asymmetric ductile–brittle transition (aDBT) is first identified in the microcutting of (111) CaF2 single crystals through a systematic experimental study of the machined surface profile, cutting force, crack morphology, and material microstructural changes. Crystal plasticity finite element method simulation has been developed to elucidate the underlying mechanism of variation in macroscopic cutting forces, meso-scale dislocation activities, and lattice rotation under the microcutting induced stress field. The characterised aDBT evokes a reflection on determining the critical chip thickness which plays an essential role in ductile-regime microcutting of brittle materials.

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