Material removal and defect evolution in nano-cutting of γ-TiAl alloy: The effect of twin boundary

Abstract

Nano-twinned materials have attracted considerable attention due to their unique plastic deformation mechanisms and the formation of prismatic dislocation loops (PDLs). However, the impact of twins on nano-cutting behavior remains inadequately understood. This paper conducts molecular dynamics simulations to investigate the material removal behavior and the evolution of PDLs in twin single-crystal γ-TiAl alloy during nano-cutting. The results show that during the cutting process of twinned TiAl alloys, PDLs are generated through multiple dislocation reactions and cross-slips, and there are two types of chips, namely regular and serrated, as well as two dislocation reaction paths, namely slip along the twin boundary and break through the twin boundary. When the cutting direction is $\left(\overline{1}\overline{1}2\right)$[111], a significant number of atoms migrate into the matrix interior, the material undergoes extrusion removal, forming regular chips and generating a large number of PDLs. When the PDLs slip to the twin boundary, they are completely blocked and slip along the twin boundary, resulting in detwinning. However, when the cutting direction is $\left(\overline{1}\overline{1}2\right)\left(\overline{1}\overline{1}\overline{1}\right)$, a large number of atoms flow upward to form chips, the material undergoes shear removal, forming serrated chips and forming incomplete PDLs. When the incomplete dislocation loops reach the twin boundary, cross-slip occurs and successfully penetrates the twin boundary. This research not only enhances the understanding of the deformation mechanisms of twin single-crystal γ-TiAl alloy during nano-cutting, but also provides new insights into the interaction between dislocation loops and twin boundaries.