Study On Hot Deformation Behavior Of Spray Formed 7055 Aluminum Alloy

7055 aluminum alloy, known as "ace aluminum alloy", is a new type of high strength aluminum alloy developed by Alcoa in the 90’s of last century, which has excellent coordination of strength, toughness and corrosion resistance. Spray formed 7055 aluminum alloy has important applications in field of aeronautics and astronautics in terms of separation of some defects like segregation and coarsen grain often occurred in traditional casting process. Up until now, the research on hot deformation behavior of spray forming 7055 aluminum alloy is rarely reported, and its hot work characteristics are not thoroughly understood.The hot deformation behavior of spray formed 7055 aluminum alloy based on the industrial production was investigated in this paper. Hot compression deformation were performed on Gleeble-3500 thermal-mechanical simulator at strain rate of 0.001s-1-5s-1 and deformation temperature of 300°C-450°C and the engineering strain was 50%. The peak stress constitutive equation of spray formed 7055 aluminum alloy was constituted and the microstructure evolution was studied by means of OM, SEM and TEM, and the hot process map was drawn based on dynamic materials model. The purpose of this paper is to provide a theoretical basis for optimization of hot work process of spray formed 7055 aluminum alloy. The main conclusions are as follows:(1) The flow stress of spray formed 7055 aluminum alloy increase with the increasing of strain rates and decrease of deforming temperature. When deforming temperature was 300°C, the peak stress (σP) increased from 57.61MPa to 177.45MPa with ε= 0.001s-1 up to 5s-1, and σp increased in like manner with the increasing of deforming temperature under the same strain rates.(2) The maximum temperature rising of spray formed 7055 alloy induced by deformation heat is 25℃ under high strain rate testing, and the corrected flow stress is 22MPa higher than measured value, and the error between two sides is 14.75%(3) After four cycles of calculation, a peak stress constitutive equation was constituted based on Arrhenius hyperbolic sine function: ε=1.7905×1010·[sinh(0.02054σ)]4.2084exp(-157785/rT) The average absolute relative error (Er) of the constituted equation is 5.26%.(4) The deformation micro structure of spray formed 7055 alloy containing a large number of dislocation cell structure at strain less than 380°C, while higher than 420°C and in Z≤27.4 occurs dynamic recrystallization. With the decrease of strain rate, the more fully the dynamic recrystallization occurred.(5) The precipitation particles in hot deformation play the role of pinning in the movement of dislocations, and the number of rodlike phases increased with the increase of temperature. While it was shown that the phases dissolved in the matrix in a certain degree when deforming temperature rised to 450°C.(6) The hot process map was built of spray formed 7055 alloy based on dynamic materials model. It has no significant difference of the hot process map between strain 0.3 and 0.6, and the power dissipation efficiency decreased rapidly in flow instability region.(7) When the strain is 0.6, it is suitable for hot work in the parameter region of 380°C-450°C and 0.006 s-1-0.082 s-1, and DRX was occurred in this region. While it is easy to produce the adiabatic shear band in the parameter region of 350°C-450°C and 0.22s-1-5s-1, which should be evaded.