Ambient- and high-temperature mechanical properties of isochronally aged Al–0.06Sc, Al–0.06Zr and Al–0.06Sc–0.06Zr (at.%) alloys

• Published in: Acta materialia Vol. 59; no. 3; pp. 943 - 954
• Main Authors: Knipling, Keith E., Seidman, David N., Dunand, David C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2011
• Subjects: Alloys; Aluminum; Aluminum alloys; Aluminum base alloys; Dendritic structure; Heat treatment; Intermetallic compounds; Isochronal heat-treatments; Microhardness; Precipitation; Scandium; Zirconium; Aluminum alloys; Precipitation; Zirconium; Isochronal heat-treatments; Scandium
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2010.10.017

Ambient- and high-temperature precipitation strengthening are investigated in Al–0.06Sc, Al–0.06Zr and Al–0.06Sc–0.06Zr (at.%) alloys. Following solidification, Sc is concentrated at the dendrite peripheries while Zr is segregated at the dendrite cores. During isochronal aging, precipitation of Al 3Sc (L1 2) commences between 250 and 300 °C for Al–0.06Sc, and reaches a 429 MPa peak microhardness at 325 °C. For Al–0.06Zr, precipitation of Al 3Zr (L1 2) first occurs between 400 and 425 °C and reaches a 295 MPa peak microhardness at 475 °C. A pronounced synergistic effect is observed when both Sc and Zr are present. Above 325 °C, Zr additions provide a secondary strength increase that is attributed to precipitation of Zr-enriched outer shells onto the Al 3Sc precipitates, leading to a peak microhardness of 618 MPa at 400 °C for Al–0.06Sc–0.06Zr. Upon compressive creep deformation at 300–400 °C, Al–0.06Sc–0.06Zr exhibits threshold stresses of 7–12 MPa; these values may be further improved by optimal heat-treatments.