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

Superplastic deformation occurs at high temperatures and requires the prese nce of a very small grain size. Experiments demonstrate that equal-channel angular (ECA) pressing is capable of introducing ultrafine grain sizes in p ure Al, Al-Mg and Al-Zr alloys, with grain sizes lying in the sub-micromete r range for the alloys. It is shown by static annealing that these ultrafin e grain sizes are not stable in pure Al and the A-Mg alloys at elevated tem peratures but in the Al-Zr alloys the grains remain small up to temperature s of approximate to 600 K. (C) 1999 Elsevier Science S.A. All rights reserv ed.