Microstructural characterization of rapidly solidified Al-Li-Co powders

摘要: A study of the combined effect alloying elements and melt superheat has been carried out on as-solidified structure rapidly solidified Al-Li-Co powders. Three alloys,viz., Al-3 pct Li, Li-0.4 Co, Li-0.8 Co were chosen, liquid in each alloy atomized from temperatures 1173 1073 K, using centrifugal atomization technique. The microstructural characterization was done light, scanning, transmission electron microscopy. Four types microstructures,viz., dendritic, cellular, equiaxed-type, featureless structures, observed by light cooling rate, as determined same, lay range 104 to 106 Ks−1, but seen go beyond 107 Ks−1 when estimated TEM micrographs. On micro-level, Al-Li powders found exhibit dendritic structures with differing morphologies, whereas low-angle cell walls perturbed interfaces main structural features alloys. Increasing both cobalt content powder particle diameter favored transition into cellular structure. zone comprised mainly elongated columnar grains (0.2 μm width 1.5 length). mechanism describing formation proposed. Aging melt-quenched at 473 K for times up 100 hours results dissolution same postulated. difference superheats chosen present work is not sufficient cause drastic changes.