Research On Mechanical Property And Microstructure Evolution In Hot Working Of 2195 Aluminum-Lithium Alloy

2195 aluminum lithium alloy is one of the third generation aluminum-lithium alloys developed by in 1989. The alloy has some advantages such as low density,high strength, high specific stiffness, good heat resistance and corrosion resistance, etc. It is considered as the ideal structural material in the aerospace industry.In this paper, the single pass cylinder uniaxial compression and plane-strain compression test at 60% reduction of 2195 aluminum lithium alloy after homogenization was conducted on the thermal simulation equipment Gleeble3500.2195 aluminum lithium alloy was deformed at temperature of 400 ℃, 420 ℃, 440 ℃, 460 ℃, 480 ℃,500 ℃ and strain rate of 0.01s-1, 0.1s-1, 1s-1, 10s-1. We studied the high temperature rheological behavior of 2195 aluminum lithium alloy in this two compression modes. Its main contents include flow stress, constitutive relations,microstructure evolution and thermal processing map of the alloy.Then comparative analysis the differences of them under the two compression modes.The study provides some theoretical guidance on the actual production process of the factory. The main results obtained are as follows:2195 aluminum alloy has steady rheological characteristics and a trend to dynamic softening in cylinder uniaxial compression and plane-strain compression process. When the temperature is constant,the peak stress and peak strain are gradually reduced with the deformation temperature increasing.The flow stress constitutive equation of the two compression modes was established and obtained the activation energy of them.The activation energy of cylinder uniaxial compression is 190.27KJ/mol,while the activation energy of plane-strain compression is 216.56 KJ/mol. Then made a brief analysis for the reasons which cause the difference of the activation energy.The microstructure of 2195 aluminum lithium alloy during hot deformation of the two compression modes showed that the dynamic recovery is the main characteristics up to 420 ℃and dynamic recrystallization above 440 ℃. The EBSD results showed that with Z value decreasing(the temperature rise or strain rate decreases),the content of small-angle grain boundary in microstructure decreased,which were transformed to high-angle boundary, therefore,the main softening mechanisms of the alloy transformed from dynamic recovery to dynamic recrystallization.The processing maps of 2195 aluminum lithium alloy at different strain and the whole deformation of the two compression modes were obtained. The processing maps show that the strain has a greater impact on rheological instability area of the two compression modes. Rheological instability region tends to increase with the strain increasing, while the security zone has a decreasing trend.Power dissipation coefficient changed little, showing little effect of strain on the power dissipation factor. The microstructure corresponding with each different region of the superimposed processing map was analyzed. The microstructure indicated that the plane strain compression is more accurately on reflecting the lab real process compared to the cylinder uniaxial compression.Considering the influence of deformation conditions under the two compression modes,and combined with the characteristics of processing maps of the two compression modes,the optimized process parameters for the 2195 aluminum lithium alloy is temperature of 440℃-500℃ and strain rate range of 0.01s-1-0.1s-1.