David J. Skinner

Effect of strain rate on tensile ductility for a series of dispersion-strengthened aluminum-based alloys

Abstract Rapid solidification processing, in the manufacture of elevated temperature aluminum alloys, results in significant supersaturation of solute elements in the aluminum matrix solid solution. These levels are shown to alter significantly the deformation characteristics of this class of alloys through the phenomenon of dynamic strain aging (DSA). That is DSA reduces tensile ductility at intermediate temperatures. The temperature ranges are found to be dependent on the solute element in solid solution and the strain rate of testing.

Stability of quasicrystalline phases in AlFeV alloys

Abstract Quasicrystalline phases have been produced in a series of ternary AlFeV and binary AlV alloys prepared by melt spinning techniques. Differential scanning calorimetry and transmission electron microscopy have been employed to characterize the thermal stability and microstructure of these phases. The stability of these phases is largely dependent on the alloy composition. The results suggest that the lattice parameter of the icosahedral phase obtained in the ternary alloys is dependent on the Fe:V ratio in the alloys.

On the nature of icosahedral phases in Al(Fe,V,Si) alloys

Abstract Icosahedral phases have been produced in a variety of Al(Fe,V,Si) alloy ribbons by planar flow casting of melts with constituent elements of high purity. Differential scanning calorimetry, X-ray diffraction and transmission electron microscopy have been used to probe these phases in detail. It is found in the binary AlFe and AlV alloys that the icosahedral edge length a is independent of composition over a wide composition range; a is about 0.508 nm and 0.526 nm in AlFe and AlV, respectively. The value for a in ternary AlFeV alloys is intermediate between these two values, and is seen to be a function of the alloy chemistry. This dependence is ascribed to a solid solution type effect wherein the Fe: V ratio in the icosahedral phases varies continuously. The addition of silicon to the ternary alloys has a minimal effect on a , but a pronounced effect in terms of reduction of stability of the icosahedral phase. The icosahedral phase transformation temperature is seen to be reduced by approximately 25 K per at.% Si.

Formation of metastable Li2Al3Y through rapid solidification processing

Abstract A microstructure composed of coherent metastable L1 2 second-phase particles in a matrix of a supersaturated Al solid solution has been produced via rapid solidification processing of AlY alloys. Splat-quenched samples of the nominal compositions Al with 1, 3, 5, and 8 at.% Y and droplet samples made with the droplet emulsion technique were characterized by differential scanning calorimetry (DSC), differential thermal analysis (DTA), scanning electron microscopy, X-ray diffraction (XRD), and transmission electron microscopy. The 5 and 8 at.% Y splat samples exhibit a uniform fine dispersion of coherent metastable L1 2 second-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 A1–3at.%Y showed an exothermic signal on first heating at around 240°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 °C in the DSC. DTA of the droplets revealed undercoolings in excess of 100 °C for the alloy composition range examined.