@Article{ Knipling-2008-1182,
  author = "Knipling, K.E. and Dunand, D.C. and Seidman, D.N.",
  title = "Precipitation Evolution in Al-Zr and Al-Zr-Ti alloys during Aging at 450--600$^\circ$C",
  journal = "Acta Materialia",
  year= "2008",
  volume = "56",
  number = "6",
  pages = "1182--1195",
  abstract = "The transformation of Al$_3$Zr (L1$_2$) and Al$_3$(Zr$_{1-x}$Ti$_x$) (L1$_2$) precipitates to their respective equilibrium D0$_23$ structures is investigated in conventionally solidified Al-0.1Zr and Al-0.1Zr-0.1Ti (at.\%) alloys aged isothermally at 500$^\circ$C or aged isochronally in the range 300--600$^\circ$C. Titanium additions delay neither coarsening of the metastable L1$_2$ precipitates nor their transformation to the D0$_{23}$ structure. Both alloys overage at the same rate at or above 500$^\circ$C, during which spheroidal L1$_2$ precipitates transform to disk-shaped D0$_{23}$ precipitates at ca. 200 nm in diameter and 50 nm in thickness, exhibiting a cube-on-cube orientation relationship with the $\alpha$-Al matrix. The transformation occurs heterogeneously on dislocations because of a large lattice parameter mismatch of the D0$_{23}$ phase with $\alpha$-Al. The transformation is very sluggish and even at 575$^\circ$C coherent L1$_2$ precipitates can remain untransformed. Mechanisms of microstructural coarsening and strengthening are discussed with respect to the micrometer-scale dendritic distribution of precipitates.",
  doi = "10.1016/j.actamat.2007.11.011"
}