Rheological behavior of a commercial AA5182 aluminum alloy during solidification

During casting of aluminum alloys, the partially solidified material is submitted to thermally induced strains that can lead to severe casting defects, such as hot tearing. In this work, carried out in the frame of the European project VIR[CAST], the rheological behavior of a partially solidified AA5182 aluminum alloy has been investigated in order to provide constitutive equations to predict hot tearing in direct chill (DC) casting. Shear and tensile experiments have been performed using specific experimental devices and procedures previously designed for Al-Cu alloys. In the small strain (< 0.2) and high solid fraction (> 0.8) domain investigated here, the mushy zone is coherent. The stress-strain behavior is therefore dominated by the viscoplasticity of the solid phase, but exhibits a significant strain hardening. The behavior of the mushy zone is modeled by a compressible constitutive equation in which an internal variable, C, representing the state of cohesion of the mush, is introduced. The model accounts for solid fraction, stress state, strain rate and strain effects. The parameters that govern the evolution of C with strain have been determined and appear to be comparable to those for Al-Cu alloys. (c) 2005 Elsevier B.V. All rights reserved.