Jc. Foley et al., FORMATION OF METASTABLE LL2-AL3Y THROUGH RAPID SOLIDIFICATION PROCESSING, Materials science & engineering. A, Structural materials: properties, microstructure and processing, 179, 1994, pp. 205-209
A microstructure composed of coherent metastable L1(2) second-phase pa
rticles in a matrix of a supersaturated Al solid solution has been pro
duced via rapid solidification processing of Al-Y alloys. Splat-quench
ed samples of the nominal compositions Al with 1, 3. 5, and 8 at.% Y a
nd droplet samples made with the droplet emulsion technique were chara
cterized by differential scanning calorimetry (DSC), differential ther
mal analysis (DTA), scanning electron microscopy, X-ray diffraction (X
RD), and transmission electron microscopy. The 5 and 8 at.% Y splat sa
mples exhibit a uniform fine dispersion of coherent metastable L1(2) s
econd-phase particles with a lattice parameter of 0.4234 nm, while the
1 at.% Y splat sample exhibits a cellular structure. Thermal cycling
of splat-quenched Al-3at.%Y showed an exothermic signal on first heati
ng at around 240-degrees-C corresponding to the partial decomposition
of the metastable structure, with some retained L1(2) phase structure
detectable by XRD following heating of the sample to 550-degrees-C in
the DSC. DTA of the droplets revealed undercoolings in excess of 100-d
egrees-C for the alloy composition range examined.