Abstract
A range of analytical techniques, including optical and electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction were used to assess the extent of segregation in gas atomised Ti–48AI–2Mn–2Nb (at.-%). The secondary dendrite arm spacing was used as a measure of microsegregation in these powders. These undercooled powders were found to solidify as hexagonal α2 dendrites, surrounded by γ phase segregate. Depending on the degree of undercooling experienced by a dendritic region and its composition, the hexagonal phase was found to transform to equilibrium γ phase by means of either a massive or a lamellar type reaction. The final relative phase distribution of the α2 and γ phases was a function of the powder particle size. The microstructure of the hipped powder reflected the inhomogeneity inherited from the starting powder material.
MST/3470
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