XFEM simulation of the effects of microstructure on the intergranular fracture in high strength aluminum alloy

A unit cell including the matrix, precipitation free zone (PFZ) and grain boundary was created, and the extended finite element method (XFEM) was used to simulate the growth behaviors of crack at grain boundary under uniaxial tensile load condition. The effects of PFZ width, particle shape, particle size, yield stress, mechanical properties of PFZ on intergranular fracture were simulated. Simulation results show that the crack extends as plane expansion under uniaxial tensile load, and the shape of crack gradually turns to be a circle. The existence of PFZ can reduce the stress intensity at grain boundary, and the failure strain of material is enhancing with the width of PFZ increasing, but the failure strain of the material without PFZ may be improved because there is no deformation localization around grain boundary. Because the crack extends as plane expansion, the crack growth in short direction is affected by the crack size in long direction, and the crack shape plays a role in influencing the crack growth direction and crack growth velocity. The increasing of yield stress in matrix makes the intergranular failure strain drop.