Precipitation evolution in Al–Zr and Al–Zr–Ti alloys during aging at 450–600 C
نویسندگان
چکیده
The transformation of Al3Zr (L12) and Al3(Zr1 xTix) (L12) precipitates to their respective equilibrium D023 structures is investigated in conventionally solidified Al–0.1Zr and Al–0.1Zr–0.1Ti (at.%) alloys aged isothermally at 500 C or aged isochronally in the range 300– 600 C. Titanium additions delay neither coarsening of the metastable L12 precipitates nor their transformation to the D023 structure. Both alloys overage at the same rate at or above 500 C, during which spheroidal L12 precipitates transform to disk-shaped D023 precipitates at ca. 200 nm in diameter and 50 nm in thickness, exhibiting a cube-on-cube orientation relationship with the a-Al matrix. The transformation occurs heterogeneously on dislocations because of a large lattice parameter mismatch of the D023 phase with a-Al. The transformation is very sluggish and even at 575 C coherent L12 precipitates can remain untransformed. Mechanisms of microstructural coarsening and strengthening are discussed with respect to the micrometer-scale dendritic distribution of precipitates. 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
منابع مشابه
Precipitation evolution in Al–0.1Sc, Al–0.1Zr and Al–0.1Sc–0.1Zr (at.%) alloys during isochronal aging
Precipitation strengthening is investigated in binary Al–0.1Sc, Al–0.1Zr and ternary Al–0.1Sc–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...
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