Effect of Additions of Zirconium, Chromium, and Nickel on the Structure and Characteristics of Superplasticity of Alloys of the Al-Zn-Mg-Cu System

By optical and transmission microscopy as well as by X-ray structural analysis, the structure and properties of alloys of the Al-Zn-Mg-Cu system with Ni, Zr, and Cr additions during superplastic deformation are investigated. It is shown that introduction of 0.26% Zr into the alloys leads to the formation of a nonrecrystallized or partially recrystallized structure in the billets. Such materials manifest the effect of superplasticity at t = 515 degrees C in a range of deformation rates of (0.15-1.0) x 10(-2) s(-1), and the relative elongation reaches 450-680%.