The Effect Of Hot Working On Microstructure And Property Of2024Aluminum Alloy

As very significant structural material used in aerospace area,2024aluminum alloyis widely used on aerospace.2024aluminum alloy is hot compressed on1500D withtemperature range at300~450℃and strain rate range at0.01~10s-1. The flow stressbehavior was studied and the flow stress model had been established. The processingmaps at different strains had also been established. Microstructure evolution of2026aluminum alloy during compression at elevated temperature had been analyzed by usingoptical microscope and EBSD electron microscope.2024sheet was hot rolled toconfirm the veracity and the practical value. The hot compressed samples and the hotrolled samples were subsequently solution treated at495℃for2h and aged for12hhours at180℃,the microstructure and mechanical properties of which were studied.○1The flow stress of2024aluminum alloy at elevated temperature increases withthe increasing strain till reaching the peak stress value and then it decreases. The valueof flow stress strongly depends on deformation temperature and strain rate. The flowstress value decreases with the temperature increasing and strain rate deceasing. Thehyperbolic sine equation and Zener-Hollonmon equation are used to describe the hotdeformation behavior of2024and the hot deformation activation energy of2024is367.37kJ/mol.○2Based on DMM model, the processing maps of2024are established and theoptimal section are confirmed. The microstructure evolution principle with deformationtemperature and strain rate is obtained: with the temperature increases, the softenmechanic of2024transform from recovery to recrystallization gradually. With the strainrate increases, the soften extent (recovery or recrystallization) become weaker. Theoptimal working section with strain0.6is with temperature370~440℃and strain rate0.005~0.01s-1○3After solute-solution and aging heat-treatment, the microstructure of hotcompressed2024differs with the LnZ value. The amount of equiaxed recrystallizationgrains increases with the increasing LnZ value. The size of equiaxed recrystallizationgrains are small at high LnZ value and bigger at low LnZ value. There still remainselongated deformed grains in low LnZ value of2024. The EBSD results indicate that inthe hot compressed2024the low angle boundaries decrease with the LnZ value and thelow CSL grain boundaries increased and then decrease with decreasing LnZ value. After heat treatment, the amount of low angle boundaries decreases significantly and the lowCSL grain boundaries decrease at first and then increase with decreasing LnZ value,which is opposite to the former.○42024aluminum alloy hot-rolled specimens and the hot rolled specimen aftersolution treatment and artificial aging, micro-structure evolution of which has beenanalyzed by OM and EBSD. The tensile test is also executed. With the deformationdegree increases, the grains are elongated and the low angle boundaries are stronger, thetensile strength increase and the elongation decrease. After heat treatment, the amountof big precipitates decrease and the amount of dispersoid increase. After heat treatment,the mechanical properties of2024increase significantly. The specimen with50%deformation increase the most with tensile strength451MPa and elongation23.48%.The EBSD results show that with the deformation degree increases the amounts of∑3and∑5increase.