Microstructural evolution of Al–Cu–Mg–Ag alloy during homogenization

Abstract

The microstructure evolution in an Al–Cu–Mg–Ag heat-resisted alloy during homogenization was studied by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and differential scanning calorimeter (DSC). The results show that severe dendritic segregation exists in Al–Cu–Mg–Ag alloy ingot. There are many eutectic phases in grain boundary and the distribution of the main elements along interdendritic region varies periodically. The main secondary phase is θ-Al 2Cu. By increasing the homogenization temperature or prolonging the holding time, the residual phases are dissolved into the matrix gradually, grain boundaries becomes sparse and all elements become more homogenized, which can be described by a constitutive equation in exponential function. The overburnt temperature of Al–Cu–Mg–Ag alloy is 510 °C. And the proper homogenizing process is 500 °C × 16 h, which is consistent with the results of homogenization kinetic analysis.