7000 series Al-Zn-Mg Cu Zr alloy was selected as the research materials,and isothermal temperature compression tests were conducted on Gleeble1500 thermal simulation testing machine at deformation temperatures of 250-400 ℃ and strain rates of 0.01-10 s-1.The research results indicate that the flow stress of the alloy increases with the increase of strain rate and decreases with the increase of deformation temperature during isothermal compression.When the strain rate was 10 s-1 and the deformation temperature was 250 ℃,the peak stress of the alloy could reach 205 MPa.Most of the true stress-strain curve exhibited the characteristics of dynamic recrystallization.Combined with TEM analysis,the forming mechanism of dynamic recrystallization was that the dislocations gradually evolve into low angle grain boundaries(2°-15°)and large angle grain boundaries(＞15°)through sliding and climbing,and relying on dislocation rearrangement to form a substructure inside the original grain.Finally,a complete grain boundary formed.The constitutive equation of Al-Zn-Mg-Cu-Zr alloy was constructed by using arrhenius model and zener hollomon parametric equation,in which the average deformation activation energy of the alloy was 324 187 J/mol.In addition,hot working diagrams of Al-Zn-Mg-Cu-Zr alloy under 0.2,0.4 and 0.6 strains were constructed by Prasad instability criterion and other models,and the machinability windows were 252-400 ℃,0.01-0.015 s-1.
Al-Zn-Mg-Cu-Zr alloyhot deformationdynamic recrystallizationtrue stress-strain curvehot working diagram
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