Influence Of Initial Microstructure On Hot Deformation Behavior Of Al-Cu-Mg-Zr Alloys

Al-Cu-Mg-Zr alloy is a new type of extruded alloy based on 2024 and 2224aluminum alloys.It decreases content of Fe and Si elements and adds a bit of Zr to inhibit the recrystallization,with higher strength and toughness,wear resistance,better fatigue resistance and workability.The initial microstructure and deformation conditions of the alloy during industrial hot deformation have a significant impact on the final microstructure and properties.In this paper,the flow behavior and hot workability of Al-Cu-Mg-Zr alloys with different initial microstructures were studied by hot deformation compression experiments combined with microstructure characterization.Based on the industrial production practice,three typical cooling methods?water quenching,air cooling,furnace cooling?were adopted after the homogenization of the rolled Al-Cu-Mg-Zr alloy,and three different precipitation phase structures were obtained.The Al-Cu-Mg-Zr alloy was separately subjected to water quenching,air cooling and furnace cooling treatment to obtain initial microstructure with different solid solubility.The isothermal thermal compression simulation experiments of these three different initial microstructures of Al-Cu-Mg-Zr alloy were carried out on a Gleeble-3500 thermal simulator with a deformation temperature of 300⁴50°C and a strain rate of 0.01¹0 s^-1.The true stress-true strain curve of the alloy under different deformation conditions can be obtained.The results show that the water-quenching alloy has the fastest cooling rate and the smallest percentage of precipitated phase,and its dynamic softening rate,peak stress and thermal deformation activation energy value are the largest;t he coarse phase exists in the furnace cooling alloy,and the percentage of precipitated phase is the largest.However,its dynamic softening rate,peak stress and thermal deformation activation energy are minimal.Then,using the Arrhenius equation model,the constitutive equations of three different initial state alloys are established.It is found that the hyperbolic sinusoidal model can describe the flow stress behavior of the alloy.The thermal activation energy Q of air cooling?AC?,water quenching?WQ?and furnace cooling?FC?alloys is 180.45,298.92 and 161.45 kJ/mol respectively.Based on the dynamic material model?DMM?theory,the thermal processing maps of three different initial microstructure alloys were drawn,and the microstructure of the deformed alloy was observed by scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.There instability?cracks,cavity,broken second phase?can be found in the processing map instability zone.