Abstract
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 α-Al matrix. The transformation occurs heterogeneously on dislocations because of a large lattice parameter mismatch of the D023 phase with α-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.
Original language | English (US) |
---|---|
Pages (from-to) | 1182-1195 |
Number of pages | 14 |
Journal | Acta Materialia |
Volume | 56 |
Issue number | 6 |
DOIs | |
State | Published - Apr 2008 |
Keywords
- Aluminum alloys
- Coarsening
- Precipitation strengthening
- Titanium
- Zirconium
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys