Research On Hot Deformation Behavior And Heat Treatment Of A Novel6000Aluminum Alloy

6000series aluminum alloy is lightweight material and widely used in vehicle boby, aerospace industry, construction, decoration, etc. A novel6000aluminum alloy which is contain Mn is studied in this paper. The effect of the different homogenization at560℃for4h and8h of this alloy on the flow stress, microstructure and apparent activation energy during hot deformation have been studied by using the hot-simulation machine, the techniques of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vicker hardness test, tensile properties test and differential scanning calorimetry(DSC). Meanwhile, the recrystallization process after cold deformation, the heat treatment have also been investigated in detail. The conclusions are summarized as follows:(1) The flow stress model of this aluminum alloy was established. The hot deformation behavior of this aluminum alloy can be described by the hyperbolic sine constitutive equation. In the temperature range within430～550℃and the strain rate range within0.001～1s-1, the apparent activation energy of this alloy is mainly affected by solid solubility of Mn because the activation energy of diffusion in Al about Mn atom is higher than the self diffusion activation energy of Al. Therefore, the apparent activation energy of the alloy which is homogenized at560℃for8h (289.99KJ/mol) is higher than that which is homogenized at560℃for4h (212.58KJ/mol). The flow-stress constitutive equation of this alloy homogenized at560℃for4h and8h can be expressed respectively as follows: ε=4.61×1022[sinh(0.0026·σ)]10.44exp(-212580/RT) ε=1.79×1030[sinh(0.0029·σ)]13.25exp(-289990/RT)(2) Under the same hot deformation conditions, homogenization at560℃for8h can reduce the flow-stress of this aluminum alloy. This indicates that using this homogenization processing can reduce the flow-stress during extrusion production. But, the tensile properties of the alloy which is homogenized at560℃for8h are lower than the alloy which is homogenized at560℃for4h.(3) The microstructure of this aluminum alloy after cold deformation presents fibrous tissue characteristic obviously. The results of recrystallization after cold deformation show that:recrystallization happens easier with higher annealing temperature, longer annealing time and larger cold deformation.(4) For this aluminum alloy, the feasible solid solution and artificial aging treatment is that:solid solution at560℃for1h and quenching in water, then artificial aging at180℃for8h. After heat treatment, its tensile strength can reach401MPa, yield strength can reach356MPa, as well as elongation about17%. Together with the DSC curves and TEM observations, we have found that the main strength phase of this alloy is still needle shaped P", and the staying at room temperature for a certain time delays the precipitation of β".