The Rheological Behavior And The Forging Process Of High Strength Aluminum Alloy High Temperature Basic Research

A1-Zn-Mg-Cu high-strength aluminum alloy with excellent fracture-and fatigue-resistance is one of the key structural materials in the modern aviation and aerospaceindustry area. It is applied to manufacture forgings with high-performances. Therefore, ithas the important significances to improve forging performance by studying of hightemperature deformation behavior, microstructure evolution and forging processes of thealloy.Isothermal compression experiments of a new A1-Zn-Mg-Cu aluminum alloy at hightemperature have been investigated by Gleeble-1500thermal simulator. OpticalMicroscope(OM)、Electronic Microscope(SEM and TEM) and X Ray Diffraction(XRD)were employed to analyze the microstructure. Flow curves of alloy at high temperatureswere obtained. Influences of hot deformation parameters on flow curves and microstructureevolution were analyzed. The constitutive equation of flow stresses and hot processing mapduring hot deformation of the alloy have been established. Main conclusions have beendrawn as follows:1. Flow stress curves of A1-Zn-Mg-Cu aluminum alloy during high temperaturecompression deformation in the range of300~450℃and0.001~1s-1strain rates present asthe near steady state curve. Hot deformation softening mechanism is dynamic recoverymainly. Flow stress decreases with increasing temperature and decreasing strain rare.2. The constitutive equation of flow stresses during hot deformation can be expressedas,1.49×1012[sinh(0.01287)]4.5537exp(1.6992105/RT)3. Microstructure evolution mechanism during hot deformation of the alloy is dynamicrecovery mainly. Hot deformation microstructure dislocation density decrease withincreasing temperature and decreasing strain rate. At high temperature, cast structuresbecome to be forged microstructures when reduction is great than50%. The greater thereduction is, the more the dynamic recrystallization is.4. Two processing domains for hot working can be found by hot processing map andmicrostructure evolution: Parameters in the range of350℃~450℃and10-3~10-2s-1can beapplied to deform cast structures; And parameters in the range of300℃~450℃and10-3~10-1s-1can be applied to deform forged structures.On the basis of above hot deformation behavior and microstructure analysis, theforging process of billets with250mm diameters and500mm height, including fourupsetting operations and three drawing operations and stretching operation, wasinvestigated by both of simulation and test methods. The simulation results show that theequivalent strain value is in the range of8.15~11.5, which is sufficient for high performanceforgings. Moreover, the results of microstructure and performance tests of forgings indicatethat properties of the forging meet requirements.