Effect of the solid-solution composition on the superplasticity characteristics of Al-Zn-Mg-Cu-Ni-Zr Alloys

The structure and superplasticity characteristics of the Al-Zn-Mg-Cu-Ni-Zr alloys with different amounts of Zn and Mg have been analyzed. It has been demonstrated that for the formation of a micrograined structure and superplasticity effects, a bimodal size distribution of particles is required, i.e., the presence of coarse eutectic particles of Al3Ni and dispersed Al3Zr particles, and also the presence of highly alloyed solid solution is obligatory. In the case of a low-alloy solid solution in the alloys of this system, the recrystallization is hampered, both at heating and at the initial stage of the alloy deformation. An increase in the amount of Zn and Mg in the aluminum solid solution stimulates the formation of finer grains, a decrease in the yield stress, an increase in the strain-rate sensitivity m, and a growth in the values of relative elongation.