Thermal stability of ultrafine-grained aluminum in the presence of Mg and Zr additions

Superplastic deformation occurs at high temperatures and requires the presence of a very small grain size. Experiments demonstrate that equal-channel angular (ECA) pressing is capable of introducing ultrafine grain sizes in pure Al, Al–Mg and Al–Zr alloys, with grain sizes lying in the sub-micrometer range for the alloys. It is shown by static annealing that these ultrafine grain sizes are not stable in pure Al and the Al–Mg alloys at elevated temperatures but in the Al–Zr alloys the grains remain small up to temperatures of ≈600 K.