Numerical simulation of fracture behavior of in-situ TiB₂ particle reinforced 2024-T4 aluminum matrix composites

The damage and fracture behavior of in-situ TiB₂ particle reinforced 2024-T4 aluminum matrix composites (TiB₂/2024-T4) with particle volume fraction of 4.17% were investigated experimentally by means of in situ tension and SEM observation. The test results show that the aluminum alloy matrix within the TiB₂ particle segregation bands breaks earlier than that in the particle sparse region. Based on such phenomenon and with the same particle volume fraction as well as the randomly distributed particles, three 2D unit cell finite element models of different segregation band widths were established. Tensile load and periodic boundary conditions were imposed. The radial return algorithm in plane stress state was deduced and applied to the elastoplastic iteration procedure. The initiation and propagation of micro matrix cracks in TiB₂ segregation bands were simulated with Rice-Tracey local failure criterion. The numerical results show that the matrix near the particle poles suffers serious damage. Particle segregation leads to rapid accumulation of matrix damage and soon grows into micro matrix cracks. The fracture strain decreases with the increase of particle segregation degree. In addition, the nonlinear part of the stress-strain curve of the TiB₂/2024-T4 unit cell model is obviously lower than the real curve, indicating that besides the mechanism of load transfer strengthening, other indirect particle reinforcement mechanisms may also enhance the strength of the material to a certain extent.