| The flow stress and evolution of the micro structures behaviors for 5A30 aluminum alloy have been investigated in this thesis by isothermal compression testing using Gleeble-1500 thermal simulator. The interdependences of flow stressσ, strainε, strain rateεand deformation temperature T have been studied by means of OM, EDAX, SEM, TEM, EBSD and regression analysis. Dynamic recovery and dynamic recrystallization of the alloy have also been discussed. The main results are as follows:1. The variable rules of flow stress for 5A30 aluminum alloy were analyzed during hot compression. The significant steady flow characteristic of 5A30 aluminum alloy exists during plastic deformation in the range of 300 to 500℃and 0.001 to 1.0s-1. The curves of flow stress appeared serrated characteristic. As increasing the deformation temperature and decreasing strain rate, the flow stress increases. The stress is sensitive to strain rate positively.2. The relationship betwwen steady flow stress and Z parameter was investigated for 5A30 alloy during hot compression. A hyperbolic sine relationship can satisfactorily correlate strain rate s and deformation temperature T with flow stressσby introducing an Arrhennius term which involves thermal activation parameters, i.e. deformation activation energy for the 5A30 aluminum alloy during hot deformation. The steady state flow stress is closely related to temperature-compensated strain rate, the so-called Zener-Hollomon parameter Z value.3. The constants of 5A30 aluminum alloy including structural factor A, stress-level coefficient a, stress exponential n and activation energy Q can be calculated. The material constants above based on regression analysis and minimized deviation method were 160.94kJ/mol,3.314,3.058x 109s-1 and 0.0184mm2/N, respectively. These material constants can be used to measure the characteristics of 5A30 alloy during hot deformation, including to describe the relationship between flow stress and Z parameter, show the deformation mechanism and provid basis for extrusion simulation.4. The steady flow stress model of 5A30 aluminum alloy at high temperature has been established. The flow stress model can be expressed as the exponential relationshipσ=2.735×104ε0.0007·ε0.1758exp(-0.0076T) and power lawσ=4.063×1016ε0.0006·ε0.1756T-5.9041, respectively, which can calculate the flow stress more accurately during hot deformation. The error of models above were less than 8%, and it can provide theory foundations for process making, mold designing and equipment selecting.5. The evolution rules of micro structural for 5A30 aluminum alloy has been investigated during hot compressive deformation. The main restoration mechanisms of the alloy are dynamic recovery and dynamic recrystallization. When the temperature is above or equal to 350℃and lnZ is low or equal to 24.47, dynamic recrystallization phenomenon can take place in 5A30 aluminum alloy, in this case, dynamic recrystallization is the predominated mechanism. The reciprocal of the mean subgrain diameter fits a general linear relationship with the natural logrithm of the temperature-compensated strain rate. This interrelation between deformation variables and consequent substructure can be utilized in prediction and control of the structure and the properties for the alloy to be hot deformation.6. The rules and reasons of deformation activation energy influenced by temperature and strain rate for 5A30 alloy during isothermal deformation were investigated. The deformation activation energy were varied with temperature and strain rate.When the temperature is 300℃, the deformation activation energy is higher. When the temperature is about 350℃, the activation energy decreased. The higher temperature is, the more activation energy increased was, which related with solution and precipitation of the second phases.
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