Microstructure, Fracture Mechanism, and Constitutive Analysis of Spray-Formed and Extruded Al-12Zn-2.4Mg-1.1Cu-0.3Zr Alloy

The microstructure, hot flow stress behavior, and fracture mechanism of spray-formed and extruded (SFEed) Al-12Zn-2.4Mg-1.1Cu-0.3Zr alloy were investigated by uniaxial tensile stress over temperature range 523-673 K and strain rate range 0.00005-0.05 s−1. The interaction among activation energy and deformation parameters was analyzed. An Arrhenius-based constitutive equation was proposed to determine the peak flow stress of SFEed Al-12Zn-2.4Mg-1.1Cu-0.3Zr alloy. The results reveal that the recrystallization degree and MgZn2 phase content as well as dislocation density for various deformation conditions are vital for peak flow stress. The studied alloy exhibits superior peak flow stress by the high alloying elements and RRA heat treatment. The transformation of fracture mechanism from void coalescence to intergranular fracture is mainly caused by the interaction between dislocation and MgZn2 phase. Low activation energy on the case of high temperature is contributed by the reduction of energy barrier for dislocation motion caused by microstructure evolution. The proposed constitutive equation can determine the peak flow stress with reasonable precision by analysis of standard statistical parameters.