A numerical model to investigate the role of residual stresses on the mechanical behavior of Al/Al₂O₃ particulate composites

Research is presented about the mechanical behavior of a 6061 aluminum alloy reinforced with alumina particles. In particular, the role of thermal-induced residual stresses on the mechanical behavior of this composite is analyzed. Experimental tests were carried out to evaluate the mechanical characteristics of this type of material under static and fatigue loading. Fractographies on broken specimens evidenced the failure mechanisms under different load conditions. Also carried out were measurements using the x-ray diffractometric (XRD) technique to determine the residual stresses due to the thermal treatment both in the matrix and in the particles. A microscale finite-element model (FEM) of this material was developed to investigate the actual stress state caused by the thermal treatment and an applied load. A comparison of the numerical results and the experimental observations helped to explain the fracture modes under static and cyclic loading and to determine the role of the residual stresses under both monotone and cyclic loads. These results suggest some treatment to improve fatigue strength of the material.