Material removal behavior of nanoscale shear cutting and extrusion cutting of monocrystalline gamma-TiAl alloy

RC Feng and ZH Shao and SZ Yang and H Cao and HY Li and CL Lei and J Zhang, INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, 119, 6729-6742 (2022).

DOI: 10.1007/s00170-021-08536-8

The theoretical research shows that brittle materials can realize ductile cutting at the nanometer scale and avoid cracks on the machined surface. However, the decrease of machining scale changes the load state and material behavior, which makes the classical shear model fail. Therefore, based on modern physical research methods such as molecular dynamics, the nano-cutting process of the monocrystalline gamma-TiAl alloy is studied in this paper. The essential difference between nano- cutting and macro-cutting is analyzed, and the material removal mechanism at nanoscale is explained, which provides theoretical support for the plastic domain machining of brittle materials. The results show that the ductile cutting process of the brittle gamma-TiAl alloy at the nanometer scale is implemented by the phase transformation under the high hydrostatic pressure near the tool. The phase transformation during the cutting process can be divided into high stress-induced amorphization (HSIA) and elastic stress-induced dislocation (ESID). Compared with shear cutting, the material removal under extrusion cutting is achieved by continuous plastic deformation in the HSIA region above the stagnation zone. The ESID process leads to the formation of subsurface defects and does not contribute to the formation of amorphous chips.

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