Study On The Plastic Deformation Behaviors Of Al-8.4Zn-2.2Mg-2.4Cu Alloy At Elevated Temperatue

The deformation behaviors and evolution behaviors of the microstructure for the new 7055 aluminum alloy at high temperatures have been investigated by isothermal compression testing method with Gleeble-1500 thermal simulator. The interdependences of flow stress a , strain rate and deformation temperature T for the alloy have been studied with the aids of OM, EDAX, DSC, XRD, TEM , SEM , regression analysis and artificial neural networks methods. Dynamic recovery and dynamic recrystallization phenomenon of the alloy have also been discussed. The main contents are as follows:1. A near steady plastic flow of the 7055 aluminum alloy was confirmed during isothermal compression deformation in the range of 250~450 C and 0.001-1.0s-1. The flow stress increases with decreasing deformation temperature and increasing of strain rate. The stress is sensitive to strain rate positively.2. The interrelations of flow stress, strain rate and deformation temperature can be described by a hyperbolic sine function =A[sinh( )]n exp( ) for 7055 aluminum alloy during the deformationprocess. The flow stress can be described by temperature-compensated strain rate, the so-called Zener-Hollomon parameter.3. Based on the interrelations of flow stress, strain rate and deformation temperature, the four constants of 7055 aluminum alloy can be calculated during the deformation process.4. The steady flow stress model of 7055 aluminum alloy at high temperature has been established by regression analysis and artificial neural networks methods, respectively. The flow stress model gotten by regressionanalysis can be expressed as = 7.57 103 exp(-0.0070T), whichcould be used to calculate the flow stress of deformation at high temperature accurately, the flow stress model got by BP neural network method could predict the flow stress more precisely.5. The characteristic of deformation microstructure at high temperatures for 7055 aluminum alloy have been studied. The condition of dynamic recovery and dynamic recrystallization took place in 7055 aluminum alloy had been explored. It was found that When the temperature is lower than 300 C and the strain rate is higher than 0.1s-1, dynamic recovery took place in 7055 aluminum alloy, and formed the relative steady subgrains. When the temperature is higher than 400 C , the strain rate is lower than 0.01s-1 and lnZ 19.9, dynamic recrystallization phenomenon took place in 7055 aluminum alloy. In this time, dynamic recrystallization is the predominated mechanisms.