Atomistic modelling of the plastic deformation of helium bubbles and voids in aluminium under shock compression

Abstract

AbstractThe characteristic plasticity associated with the deformation of helium bubbles and voids in aluminium under shock compression is investigated by molecular dynamics (MD) simulations. The scenarios indicate that the emission of shear dislocation loops rather than prismatic loops is the mechanism by which helium bubbles and voids collapse. The tendency to favour dislocation nucleation and emission at the trailing side of a void but at both sides of a helium bubble is attributed to the distribution of the resolved shear stress along (111) planes. Under the same loading strength, the resolved shear stress of the leading side of a helium bubble is larger than that of a void due to the internal pressure of the bubble; therefore, the dislocation nucleation at the leading side of a helium bubble is easier than that for a void. Based on the Virial theorem, we find that the locations of the calculated maximum resolved shear stress are in good agreement with the locations of dislocation nucleation. The elastic model clearly shows that the resolved shear stress increases with the internal pressure of the helium bubble but that the location of the maximum resolved shear stress is not affected. The results from the model nicely explain the scenarios that emerged in our MD simulations. The detailed studies of the microscopic mechanism of plastic deformation are important to deeply understand the mechanical properties of irradiated materials.Keywords: microporous materialmolecular dynamicsdeformationPACS:: 61.72.Qq61.72.Lk62.50.+p62.20.Fe AcknowledgementsThe authors sincerely appreciate the support of the high-performance grid computing platform of Henan Polytechnic University and the support from the National Natural Science Foundation of China (Grant Nos. 11147167, 51202058 and 51271073), The Natural Science Research Project of Education Department of Henan Province (Grant No. 2011A140007) and Funds of Introduction of Talents of Henan Polytechnic University (No. Y2009-1).