Effect of Er additions on the precipitation strengthening of Al-Hf alloys

Precipitation strengthening was investigated in dilute Al-Er, Al-Hf and Al-Er-Hf alloys. Combined addition of 0.045 at.% Er and 0.18 at.% Hf in Al gives a maximum hardness of 640 MPa, which is significantly higher than that of the Al-0. 18Hf and Al-0.045Er alloys. The remarkable strengthening can be attributed to the addition of Er, which accelerates the precipitation kinetics and stimulates the decomposition of Al-Hf. The effect of Er and Hf on precipitation strengthening in Al-Er-Hf alloys is discussed. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.