High strain rate superplasticity of a Zn–22 wt.%Al–x wt.%Ag alloys

The present work investigated the microstructural evolution and mechanical properties of ternary Zn–22 wt.%Al–x wt.%Ag (x = 1.0 and 4.24 wt.% Ag) alloys. The aim is to advance in the understanding of the relationship that takes place between the tension at strain rates from 1 × 10−5 to 10 s−1 at 230 °C, and silver content. The microstructure of the x = 1.0 wt.% Ag alloy consisted of two solid solutions, an α-aluminum solid solution and a η-zinc solid solution. In the x = 4.24 wt.% Ag alloy, an intermetallic AgZn3 compound was present in addition to the α and η solid solutions. The presence of silver proved to have great influence on the resultant stress versus strain rate curve, which showed high values of elongation at high strain rate superplasticity (HSRS). The experimental results suggested that the origin of HSRS was related to microstructural refinement which, in turn, was produced by the silver content. The microstructures of the alloys under study were observed in deformed and undeformed samples by scanning electron microscopy (SEM), X-ray analysis was used to investigate the deformation mechanisms involved.