Deformation behavior and microstructure of an Al-Zn-Mg-Cu-Zr alloy during hot deformation

The hot deformation behavior and microstructures of AI-7055 commercial alloy were investigated by axisymmetric hot compres-sion at temperatures ranging from 300℃ to 450℃ and strain rates from 10~(-2) to 10 s~(-1), respectively. Microstruetures of deformed 7055 alloy were investigated by transmission electron microscopy (TEM). The dependence of peak stress on deformation temperature and strain rate can be expressed by the hyperbolic-sine type equation. The hot deformation activation energy of the alloy is 146 kJ/mol. Moreover, the flow stress curves predicted by the modified constitutive equations are reasonably consistent with the experimental results, which confirms that the proposed deformation constitutive equations can provide evidence for the selection of hot forming parameters. TEM results indicate that dy-namic recovery is the main softening mechanism during hot deformation.