Study on the growth behavior of voids located at the grain boundary

The growth behavior of voids located at the grain boundary was numerically simulated with three dimensional crystal plasticity finite element model, which was implemented with the rate-dependent crystal plasticity theory code as user material subroutine. A three dimensional (3D) bicrystal model was created to simulate the growth behavior of voids located at the grain boundary and the plastic deformation distribution around the voids, and the effects of crystallographic orientation and the angle 0 of the grain boundary direction with respect to the tensile axis on fracture mode were analyzed. Under uniaxial tension condition, the unit cell with 0 = 0 degrees tends to fail by transgranular fracture, and the unit cell with 0 = 45 degrees is more likely to fail by intergranular fracture. With the orientation factor's difference between the two grains increasing, larger heterogeneous deformation may occur between the two grains, which leads to large equivalent plastic deformation along the grain boundary, and the unit cell tends to fail by intergranular fracture. Under triaxial tension condition, the void with a spherical initial shape develops an irregular shape, and sharp corners started from the internal surface of the void are induced along the grain boundary. Results show that the maximal plastic deformation at the corners is related to the crystallographic orientation and misorientation. (C) 2009 Elsevier Ltd. All rights reserved.