Effect of grain boundary doping/segregation on the mechanical behavior of Ta bicrystal

Abstract

The introduction of foreign atoms significantly alters the grain boundary (GB) behavior in materials, consequently affecting their mechanical properties. However, the effects of random doping and GB segregation of foreign atoms on deformation mechanisms and mechanical properties remain unknown. In this work, the GB behavior and deformation mechanisms of Ta bicrystals under various element doping and segregation conditions were investigated using molecular dynamics simulation. The results reveal that the deformation mechanism of pure Ta bicrystals involves dislocation slip and twinning initiated from GBs. Notably, both GB doping and segregation induce BCC to FCC phase transformations, which is attributed to the non-uniform displacement of atoms in the {112} plane along the 〈111〉 direction. Doping with W and Mo elevates the yield stress, whereas doping with Nb exhibits an inverse effect. Remarkably, the segregation of W, Mo, and Nb significantly enhances mechanical properties, surpassing the effects of GB doping. This segregation modifies the GB composition, reduces GB energy, and enhances GB stability. Our study sheds light on the pivotal role of GB doping and segregation in improving the mechanical properties and understanding the deformation mechanisms of nanocrystalline materials, offering vital insights for future material design and engineering.