Constitutive equations for creep and plasticity of aluminum alloys produced by powder metallurgy and aluminum-based metal matrix composites

TLDR: In this article, the constitutive relationship between stress, strain rate, and temperature was analyzed to obtain a unified description of aluminum alloys produced by powder metallurgy and of aluminum-based metal-matrix composites.

Abstract: The constitutive relationships between stress, strain rate, and temperature were analyzed to obtain a unified description of creep and plasticity of aluminum alloys produced by powder metallurgy and of aluminum-based metal-matrix composites. As both classes of materials are characterized by the existence of a threshold stress (σ 0), a unified description of creep (low strain-rate regime) and plasticity (high strain-rate regime) was obtained by substituting the conventional power-law equation with the sinh relationship, where the applied stress is replaced by the difference between the applied stress and a threshold stress. The stress exponent was n = 3 or 5, and the activation energy was equivalent to the activation energy for self-diffusion or to the activation energy for diffusion of solute elements in the matrix. The model was applied to an unreinforced alloy (2014PM) and a composite (6061 + 20 pct Al2O3) tested in tension (under constant load) or torsion (at constant strain rate) in the temperature range between 300 °C and 500 °C. The results were compared with data available in the literature.