Precipitation Evolution in Al-0.1Sc, Al-0.1Zr and Al-0.1Sc-0.1Zr (at.%) Alloys During Isochronal Aging
NAVAL RESEARCH LAB WASHINGTON DC MULTIFUNCTIONAL MATERIALS BRANCH
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Precipitation strengthening is investigated in binary Al-0.1Sc, Al-0.1Zr and ternary Al-0.1-c-0.1Zr at. alloys aged isochronally between 200 and 600 C. Precipitation of Al3Sc L12 commences between 200 and 250 C in Al-0.1Sc, reaching a 670 MPa peak microhardness at 325 C. For Al-0.1Zr, precipitation of Al3Zr L12 initiates between 350 and 375 C, resulting in a 420 MPa peak microhardness at 425-450 C. A pronounced synergistic effect is observed when both Sc and Zr are present. Above 325 C, Zr additions provide a secondary strength increase from the precipitation of Zr-enriched outer shells onto the Al3Sc precipitates, leading to a peak microhardness of 780 MPa at 400 C for Al-0.1Sc-0.1Zr. Compositions, radii, volume fractions and number densities of the Al3Sc1 xZrx precipitates are measured directly using atom-probe tomography. This information is used to quantify the observed strengthening increments, attributed to dislocation shearing of the Al3Sc1 xZrx precipitates.
- Metallurgy and Metallography