Investigation on the surface damage mechanism of single-crystal γ-TiAl alloy with pore defects based on nanocutting

Abstract

The γ-TiAl alloy is highly regarded as one of the most promising materials in the aerospace industry. Nonetheless, pore defects are an unavoidable challenge during its manufacturing process. To thoroughly examine the impact of these defects on the surface damage mechanism during the nanometric cutting of γ-TiAl alloy, this study utilizes molecular dynamics (MD) simulations to analyze the nanometric cutting of single-crystal γ-TiAl alloy containing pore defects. The research explores the influence of various cutting parameters and pore defect radii on cutting forces, atomic migration and surface morphology, stress and strain, sub-surface defect evolution and atomic phase transformation, and dislocation dynamics, with the goal of clarifying the surface damage mechanisms in nanometric cutting.The findings indicate that as the pore defect radius increases, the disparity between Fx and Fz becomes more pronounced, the Von Mises stress within the chip decreases, and the thickness of the sub-surface defect structure layer diminishes. When the pore defect radius is 15 Å, a "shear-off" phenomenon is observed on the cutting surface, with Fx values ranging from 2.5 to 7 times those of Fz. An increase in cutting depth results in a broader side flow width of the surface chip, raising the proportion of atoms from layers without pore defects within the chip. At a cutting depth of 20 Å, the matrix with larger pore defects shows a distinct strain distribution profile. The atomic structure of the matrix primarily consists of FCC-structured atoms.At high cutting speeds, when the pore defect radius is 10 Å, an increase in cutting depth from 10 Å to 30 Å leads to a 7.9 % rise in amorphous structure atoms. During the cutting process, dislocations predominantly occur in the shear slip zone and near the pore defects. At a cutting speed of 50 m/s and a cutting depth of 10 Å, the density of 1/6<112>(Shockley) dislocations for a pore defect size of 15 Å is 2.24 times that of a 10 Å defect; at a cutting depth of 30 Å, the density of 1/6<112>(Shockley) dislocations for a 10 Å pore defect is 2.15 times that of a 15 Å defect.