An Investigation On Alloying And Hot Deformation Behavior Of2297Aluminum Alloy

Abstract:In this paper,2297aluminum alloys containing different contents of Cu and Li and alloys with and without Zr and Er were prepared by ingot metallurgy processing. The effects of Cu and Li content and the addition of Zr and Er on the microstructure and mechanical properties of2297aluminum alloy were studied using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), hardness and tensile strength. The hot deformation behavior of2297aluminum alloy was investigated by isothermal compression on a Geeble-1500thermo-mechanical simulator. The microstructural evolution during hot deformation was studied by OM. Based on the data from true stress-true strain curves, the constitutive models were established. In order to provide guides for hot processing procedure, hot processing maps were drawn. The main conclusions are as follows:1) The main precipitates in aged2297aluminum alloy are Al2CuLi(T1) phase. For T6peak-aged alloy, the size of T1phase is large and number density is low. The grain boundary of T6peak-aged alloy is straight and exists few precipitates. For T8peak-aged alloy, T1phase is densely distributed and the grain boundary is a little curved and exists plenty of precipitates.2) The strength of2297aluminum alloy increases with the increase of Cu and Li contents. When the contents of Cu and Li are in middle level of the composition range, the alloy performs the optimal comprehensive mechanical property. For T6peak-aged alloy, ultimate strength is420.3MPa, yield strength is338.5MPa and elongation percentage is13%. For T8peak-aged alloy, ultimate strength is466.4MPa, yield strength is419.6MPa and elongation percentage is12.5%.3) The addition of0.12wt.%Zr to Al-Cu-Li alloy can significantly refine the grain size of as-cast alloy, while the addition of Er can only refine dendritic structure. By joint addition of Zr and Er, the nanosized precipitates precipitating during homogenization can improve the recrystallization resistance and strength of Al-Cu-Li alloy. The ultimate strength of T6-aged Al-Cu-Li alloy with Zr and Er is435.8MPa, which is12.8%higher than that of alloy without Zr and Er.4) The flow stress of2297aluminum alloy decreases with the increase of deformation temperature and increases with the increase of strain rate. Based on the compression data, the modified Johnson Cook model, strain-compensated Arrhenius-type model and BP-ANN model were established to describe the flow stress of2297aluminum alloy. By validity evaluation, BP-ANN model shows excellent performance and can be applied to understand and predict the flow behavior of2297aluminum alloy.5) The instability domains for hot processing of2297aluminum alloy consist of two parts:300-340℃and0.01-1s-1,350-500℃and1-10s-1. Peak efficiencies concentrate on domains at high temperature and low strain rate (450-500℃and0.01-0.1s-1), which is most suitable for hot processing procedure.