Large Aircraft Of 2024 Aluminum Alloy Thick Plate Heat Treatment Process And Hot Rolling Simulation Study

The effect of homogenization treatment, heat treament, prestretching treatment on the structure and properties of large aircraft2024aluminum alloy thick plate and temperature field, stress field finite element simulation of hot rolling process of large aircraft2024aluminum alloy thick plate were studied in this thesis. The main experimental methods:mechanical properties test at ambient temperature, hardness test, microstructure observation, transmission electron microscopy(TEM), scanning electron microscope(SEM) and DSC test, thermal simulation, ABAQUS finite element simulation. The conclusions were as follows:(1)Casting2024aluminum alloy has a serious element segregation, The degree of element segregation in order is:Cu, Mg, Mn.there are a large number of non-equilibrium phases Al2Cu and Al2CuMg at the grain boundaries.(2)According to the kinetic curves of homogenization and experiments, we can obtain the homogenizing treatment of large aircraft2024aluminum alloy thick plate is495℃/24h. After this homogenizing treatment, non-equilibrium phases are dissolved, the alloying elements are more evenly distributed.(3)The heat treatment have a strong effect on the mechanical properties of2024aluminum alloy hot-rolled thick plate. The main strengthening phases of it are S’and θ’. When the solution system is490℃/80min, aging system is185℃/12h, we can get the best mechanical properties,tensile strength, yield strength and elongation are428Mpa,325Mpa and16%respectively.(4)The prestrectch treatment of2024aluminum alloy hot roll-ed thick plate are as follows:1%,1.5%,2%,2.5%,3%.The time of peak aging of this alloy is prolonged.(5)The microstructure of prestretching treatment and non-prestretching treatment are as follow:the precipitated phases in the under aged are GP zone and T phase; the peak-aged stage GP zone changes for the short stick S" phase, alloys precipitations are S" phase and T phase, so that the alloy has the highest tough degree; In the overaging stage, S" phase and T phase coarsen, and the T phase particles dissolve partly.(6)Under the nature aging, because of σb is relatively high, σ0.2is relatively low, the ratio (σ0.2/σb) is relatively low, the prestretching of2024alloy by2%can achieve high strength and ductility.(7)2024aluminum alloy is strain rate sensitive materials. Under the same strain rate, the true stress increased with the deformation temperature decreased; Under the same deformation temperature, the true stress increased with strain rate increased. Temperature strain rate and deformation temperature have a strongly influence on flow stress when temperature deformation.The follow stress could be expressed by hyperb-olic sine form of Arrhenius equation.We can achive the material constants of2024aluminum alloy:A=0.01611s-1, n=4.23742、 Q=144.67KJ/mol、 a=0.0145Mpa-1.(8)According to the material constants which are obainted by the thermal simulation, we do the experiment of the finite element simulation of hot rolling process of2024aluminum alloy thick plate, we have achieved that the sueface temperature of the alloy has a dramatic change, internal temperature are rising constantly; along the rolling direction, the equivalent stress of contact deformation is higher than the undeformation ares and after rolling ares;along the thickness direction,the internal stress value is larger than the external,so that the alloy has the stretch effect.