Void growth and coalescence in f.c.c. single crystals

Abstract

In this study, we investigate deformation behavior of f.c.c. single crystals containing microvoids by using three-dimensional finite element methods. The unit cell analysis has been conducted to study the effect of stress triaxialities, crystallographic orientations and initial void volume fractions on the growth and coalescence of voids in f.c.c. single crystals. The locally homogeneous constitutive model for the rate-dependent single crystal plasticity is implemented into a finite element program (ABAQUS) by means of the user-defined subroutine (UMAT). To identify the effect of stress triaxiality and the crystallographic orientation on the void evolution, the stress triaxiality was kept constant during deformation. The numerical results showed that the stress triaxiality and the deformation mode specified by the crystallographic orientation have a competitive effect on the evolution of voids. For the low level of stress triaxiality, the deformation mode is mainly determined by the crystallographic orientation. For high stress triaxiality, however, the deviation from the specific deformation mode is large even for incipient void growth and the void growth rate is mainly determined by stress triaxiality and the initial void volume fraction. For the small initial void volume fraction, the growth rate of a void is rapid compared with the large one and the effect of the initial crystallographic orientation is significant.