Molecular dynamic study on strength of coincidence grain boundaries
Saitoh Ken-ichi; Kitagawa Hiroshi; Nakatani Akihiro; Ogata Shigenobu
Abstract:Atomistic simulation of coincidence grain boundary (CSL grain boundary) on tensile strength is executed. Molecular dynamics based on the effective medium theory (EMT) for aluminum which contains no empirical parameter is applied. For two tilt axes, which are chosen to be [100] and [110] , the CSL grain boundary with S= 5 - 41 and S= 3 - 33, respectively, are investigated. The estimated grain boundary energy and the surface energy agree well with the previous studies. For the fracture energy estimated from tensile loading simulation, Griffith's criterion for brittle fracture gives the lower limit. And for S= 3(A) and S= 11(A) grain boundaries, which have extraordinarily small grain boundary energy, the amount of plastic work is several times larger than that for the other grain boundaries. It is also supposed that deformation constraint influences the brittleness and ductility of bicrystal enormously. And it is demonstrated that, when brittle fracture occurs, the effect of pre existing grain boundary energy on the fracture strength becomes prominent. Key Words:molecular dynamics, effective-medium theory, aluminum, grain boundary, surface grain boundary fracture, plastic work