Research On Constitutive Relationship And Deformation Behavior Of 2198 Al-li Alloy

2198 aluminum-lithium alloy is the third generation aluminum-lithium alloy, which has been used in the aerospace and aviation industry. The deformation resistance of 2198 Al-Li alloy is sensitive to temperature and strain rate. This leads to difficulty of deformation. Currently, the report about deformation behavior of 2198 aluminum-lithium is little. Therefore, the investigation of deformation behavior and mechanism for 2198 Al-Li alloy during plastic deformation and its constitutive relationship are very important for new aviation materials research and application.In this paper, the microstructure and property of 2198 Al-Li alloy were studied by means of OM, XRD, tension tester, SEM, TEM. The range of temperature is 20～400℃, the strain rate ranges from 0.1s-1 to 0.00001s-1and the behavior of tension deformation of the alloy was discussed. At last, the coefficients of constitutive model were determined based on Field-Backofen and hyperbolic sine model, by means of statistic regression and existing date. The following conclusions can be drawn:(1)The microstructure of 2198 (T851) Al-Li alloy sheet are horizontal banded structure. It has high strength and ductiliy.(2)During the tensile deformation, deformation temperature and strain rate have great influence on deformation behavior. The flow stress decreases with the increase of temperature and strain rate. Elongation increases with the increasing of temperature, and increased with decreasing of strain rate. Recrystallization occurs during tensile deformation at a high temperature and T1 phase dissolved in matrix.(3)The fracture of the alloy appears obvious hierarchical characteristics, with dimple, when tension specimen at Room temperature. During High temperature deformation, on fracture surface, a large number of sample holes can be found. And holes enlarge with the extension of time.(4)Based on Fields-Backofen and hyperbolic sine model, by means of statistic regression and existing date, constitutive equation for deformation behavior was established and activation energy was obtained.