Precipitation evolution of Al-Zr-Yb alloys during isochronal aging

Precipitation strengthening in Al-Yb, Al-Zr and Al-Zr-Yb alloys aged isochronally between 100 and 550 degrees C was investigated. The Al-0.08 at.% Zr-0.03 at.% Yb alloy shows double-peak age strengthening behavior and obtains its second peak hardness of 379 MPa at 475 degrees C, which illustrates significant precipitation strengthening and thermal stability. The critical coherency transition radius of Ll(2)-ordered Al-3(Zr,Yb) precipitates is larger than that of Al3Yb. The synergetic effect of Yb and Zr on the precipitation evolution in Al-Zr-Yb is discussed. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.