Creep of Al-Sc Microalloys with Rare-Earth Element Additions
Cast and aged Al-Sc microalloys are creep-resistant to 300, due to the blocking of dislocations by nanosize, coherent Al3Sc (L12) precipitates. Rare-earth elements substitute for Sc in these precipitates, leading to a higher number density of smaller precipitates, which have a greater lattice-parameter mismatch with Al than in the Al-Sc binary microalloy. This leads to an improvement in both ambient temperature microhardness and high temperature creep. Creep threshold stresses of Al-Sc-RE (RE = Y, Dy, or Er) at 300 are higher than for Al-Sc and Al-Sc-M (M = Mg, Ti, or Zr) microalloys. This is in agreement with a dislocation climb model that includes the elastic stress fields of the precipitates.
W.J. Poole, M.A. Wells and D.J. Lloyd
R. A. Karnesky, D. N. Seidman, D. C. Dunand, "Creep of Al-Sc Microalloys with Rare-Earth Element Additions", Materials Science Forum, Vols. 519-521, pp. 1035-1040, 2006