Study On 2196Al-Li Alloy Extrusion Process/Die Parameter Optimization And Microstructure Properties

2196 Al-Li alloy is currently one of the most advanced light alloy materials in the world.It belongs to the typical third-generation aluminum-lithium alloy material.Compared with traditional aluminum alloy,it has lower density,higher elastic modulus,specific strength and stiffness,as well as good corrosion resistance,widely used in aerospace and other fields.The floor beams of Airbus A380,fuselage girders,pillars and seat rails of Comac C919,as well as parts of structural cabin of Tiangong-1 are made of Al-Li alloy,which reduces the overall weight by more than 10%,improves the aircraft performance,and saving the operating costs.The development of Al-Li alloy in China started late.Although it can independently produce advanced Al-Li alloy ingots,it still has a large gap with the world's sophisticated level in terms of processing and manufacturing technology.Most of the aluminum-lithium alloy structural parts used in the aerospace field are extruded profile.At present,our country is still unable to independently manufacture high-performance Al-Li alloy profile and highly relies on foreign imports.The extrusion process of Al-Li alloy profile is a non-linear forming process under the conditions of large deformation,high temperature,high pressure and complex friction coupled with multiple fields and scales,its technological level determines the final quality of profile products.The optimization design of the extrusion die structure,process parameters and the subsequent heat treatment process of the extruded profile are the key technologies of the entire manufacturing process.This paper systematically studies the hot extrusion deformation law,microstructure and mechanical properties of 2196 Al-Li alloy profiles.(1)For the three typical aluminum-lithium alloy profiles,a finite element simulation model of the steady-state extrusion process is established.Combining experimental design methods and artificial intelligence algorithms,the influence of die structure(the shape and distribution of the split holes,the height of the welding chamber,the location of the die holes,and the length distribution of the work bearing)and process parameters(extrusion speed and temperature,Preheating temperature of die and billet container,and extrusion ratio)on the physical fields(material deformation,temperature distribution,extrusion load and die stress)was studied.At the same time,corresponding multi-objective optimization methods are established.(2)Taking an H-shaped solid profile as the research object,extrusion experiments under different process parameters were performed to verify the reliability of the simulation optimization results.The surface quality and dimensional accuracy of the extruded profile were great.The influence of process parameter on the microstructure of the profile(grain size,orientation angle distribution,texture type and strength,fracture morphology)and mechanical properties(tensile strength,elongation and micro hardness)was studied.(3)The influence of single-stage and double-stage aging treatment processes(aging temperature and aging time)on the microstructure(fracture morphology,element distribution,type,morphology and distribution of precipitated phase)and mechanical properties of the profile were studied.Aiming at this kind of extruded profile,the two-stage aging treatment process was studied,and the superiority of the two-stage aging treatment over the single-stage aging process on improving the strength and toughness of this alloy was analyzed,and finally determined the best two-stage aging treatment process.