Dynamic softening and microstructural evolution during hot deformation of Al-Cu-Mg-Zr alloys with different homogenization cooling rates

An Al-Cu-Mg-Zr alloy, which obtained different homogenization cooling rates by changing the heat-treated sample size, was compressed to various strains at the deformation temperature of 300 oC and strain rate of 0.01 s(-1). The results showed that the homogenization cooling rate had strong effects on the hot deformation behavior of the alloy. The flow stress and relative dynamic softening rate of the alloy were significantly higher under a high cooling rate (HCR) than those under a low cooling rate (LCR). Furthermore, based on X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermodynamic equilibrium phase calculation, the substructure evolution in the grain interior, morphology, and spatial distribution of the precipitates were studied to determine the differences in the flow softening mechanism. The main softening mechanism could be summarized as dynamic recovery and precipitation coarsening for the LCR alloy and dynamic precipitation for the HCR alloy.