Effect of fabrication conditions and Cr, Zr contents on the grain structure of 7075 and 6061 aluminum alloys

The correlation between compression conditions at temperatures in the range of 573-773 K with the strain rate range of 0.002-2 s(-1) and grain size after solution heat treatment of 7075 alloy was investigated, as contrasted with 6061 alloy. The grain coarsening occurred under specific Zener-Hollomon (Z) parameters of 5 x 10(10)-10(12) s(-1) for 7075 alloy, 10(8)-2 x 10(12) s(-1) for 6061 alloy, respectively. These phenomena could be explained by crystalline orientation analysis and stored deformation strain evaluation. The site of sub-grains with less than 15 degrees misorientation and stored strain after compression increased, but the site of recrystallized grains after solution heat treatment increased with Z parameter. Small Z parameter condition could get low stored strain with fine grain which is stable during SHT. Effect of Cr and Zr on the grain structure of 7075 alloy was also investigated. Cr or Zr addition could inhibit the grain coarsening. The role of Zr addition was confirmed to pinning effect of Al(3)Zr dispersoids to subgrain boundaries. (C) 2008 Elsevier B.V. All rights reserved.