Study Of Thermal-mechanical Behavior And Texture Evolution In AA2099 Aluminum-Iithium Alloy

Compared with traditional aluminum alloys,the novel aluminum-lithium?Al-Li?alloys are widely used in aerospace industry,due to their higher specific strength,specific stiffness and damage resistance,improving the pay load and fuel efficiency of the aircraft.As for the researches of aluminum-lithium alloys,thermal-mechanical behaviors have been one of hotspots,its achievement help to obtain good performance of Al-Li alloy.In present study,an extrusion bar of AA2099 aluminum-lithium alloy was selected as initial material.To construct the constitutive equation and processing map of the as-extruded alloy,isothermal compression tests were conducted by a Gleeble-3800 thermal-mechanical simulator.Systematical study of thermal-mechanical behaviors and microstructure characteristics was carried out,providing the theoretical support for production of Al-Li alloys.The hot rolling texture evolution of sheets suffering different aging treatments were also discussed.Following conclusions have been drawn from the study:?1?The true stress-strain curve of as-extruded AA2099 Al-Li alloy at temperatures ranging from 360?to 520?and strain rates ranging from 0.001s^-1 to 10s^-1 exhibits that the flow stress increase with increasing deformation temperature and decreasing strain rate,shows the positive strain rate sensitivity.At strain rate of 0.001s^-1 or 10s^-1,the curves show characteristics of dynamic recrystallization?DRX?,at strain rate of 0.01s^-1,0.1s^-1 or1s^-1,the curves show characteristics of dynamic recovery?DRV?.The thermal activation energy of the alloy is 152.3kJ/mol,the constitutive equation of the alloy is:???=2.91972×10¹⁰×[sinh?0.01707??]^5.31834×e??152309.09/RT???2?The maximum power dissipation factor of the as-extruded AA2099 Al-Li alloy is0.39,near by the temperature of 520?and strain rate of 0.001s^-1.The flow instability regions correspond to regimes at 1s^-1-10s^-1 in the entire temperature range and the regions correspond to regimes at temperatures ranging from 360?to 420?and strain rates ranging from 0.001s^-1 to 0.0015s^-1.The optimum hot-working regimes are:a.at 480?-520?and 0.001s^-1-0.1s^-1 for the restoration mechanism of DRX;b.at 420?-460?and0.09s^-1-0.3s^-1 for the restoration mechanism of DRV.?3?The hot rolling texture intensity of the as-extruded AA2099 Al-Li alloy which experience different aging treatment decrease with increase aging temperature and time,increase aging time result in the move towards the direction of decrease angle?₂ of the texture intensity peak.