Precipitation evolution in Al-0.1Sc, Al-0.1 Zr and Al-0.1Sc-0.1Zr (at.) alloys during isochronal aging

摘要

Precipitation strengthening is investigated in binary Al-0.1Sc, Al-0.1Zr and ternary Al-0.1Sc-0.1Zr (at.%) alloys aged isochronallybetween 200 and 600 ℃. Precipitation of Al_3Sc (L1_2) commences between 200 and 250℃ in Al-0.1Sc, reaching a 670 MPa peak micro-hardness at 325℃. For Al-0.1Zr, precipitation of Al_3Zr (L1_2) initiates between 350 and 375℃, resulting in a 420 MPa peak micro-hardness at 425-450℃. A pronounced synergistic effect is observed when both Sc and Zr are present. Above 325℃, Zr additionsprovide a secondary strength increase from the precipitation of Zr-enriched outer shells onto the Al_3Sc precipitates, leading to a peakmicrohardness of 780 MPa at 400℃ for Al-0.1Sc-0.1Zr. Compositions, radii, volume fractions and number densities of. the Al_3(Sc_(1-x),Zr_x) precipitates are measured directly using atom-probe tomography. This information is used to quantify the observedstrengthening increments, attributed to dislocation shearing of the Al_3(Sc_(1-x)Zr_x) precipitates.