Mechanical behavior of Al 2O 3-particle-reinforced 6061 aluminum alloy under uniaxial and multiaxial cyclic loading

Abstract

Uniaxial and biaxial (proportional and non-proportional) strain-controlled tests were conducted to obtain mechanical properties of 6061 aluminum alloy reinforced with Al 2O 3 particles with 0.1 and 0.2 volume fractions. Thin-walled specimens were heat-treated in three groups, i.e. fully annealed (T0), solution and precipitation (T6) and as-extruded (F). The results indicaie that this composite material essentially has isotropic elasto-plastic properties similar to those of the matrix constituent, the aluminum alloy. It is rate-insensitive at room temperature. Under cyclic loading the composite strain-hardens during almost the entire cyclic life and it does not show a stable state for specimens prepared under F and T0 conditions. For T6 heat-treatment, cyclic hardening occurs only during the ftrst few cycles and thereafter the response is stable until failure. More strain hardening was observed under biaxial non-proportional cyclic loading in comparison with proportional cyclic loading. A fall in the elastic modulus is observed during cyclic loading with a relatively larger cyclic plastic strain, especially in biaxial cyclic loading in specimens with T0 and F conditions. Mechanisms of damage caused by the biaxial stress state are discussed on the basis of microscopic observations.