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 et al., "Creep of Al-Sc Microalloys with Rare-Earth Element Additions", Materials Science Forum, Vols. 519-521, pp. 1035-1040, 2006