Molecular dynamics study on tensile strength of twist grain boundary structures under uniaxial tension in copper

Abstract

Grain boundaries (GBs) play an important role in deformation responses and mechanical properties of materials. However, the lack of experimental observations of GBs restricts the in-depth understanding on the mechanical behavior of twist GBs and the continuum misorientation effect on the tensile strength of grains. In this paper, the <001>, <101> and <111> twist grain boundary structures for copper are studied by molecular dynamics simulations to obtain the tensile strength and intergranular stress. Over all the twist GB structures, <111> Σ3 GB structure is verified and analyzed to possess the maximum tensile strength, the lowest GBE (grain boundary energy) and the minimum CSL (coincident site lattice) value. The distribution of normal stress on GBs is further investigated to reveal the calculated results that the tensile strength is enhanced with increasing the twist angle for the <001> and <101> twist GB structures, but the misorientation has no significant influence on the tensile strength of almost all <111> twist GB structures, except Σ3. This work provides a fundamental information for understanding the effects of misorientation on interfacial stability and mechanical behaviors of grain boundary structures with different crystal directions.