Abstract
The morphological characteristics of so called duplex titanium aluminide (TiAl3) particles in several Al–5Ti–1B (wt-%) master alloys in the form of rods have been investigated using a wide range of microscopical techniques. It has been found that both rough blocky and faceted blocky aluminides are present in such materials and that hexagonal platelets are entrained within these blocky aluminides. Auger spectroscopy and transmission electron diffraction have confirmed that the platelets are diborides. In previous work, it has been suggested that duplex aluminides are particularly effective in promoting grain refinement during solidification. To investigate this, a master alloy containing duplex blocky aluminides was briefly remelted and recast from a range of temperatures. This resulted in the formation of significantly different aluminide types. When the original and remelted alloys were tested in commercial purity Al, using standard procedures, it was found that the presence of duplex aluminides does not, in itself, seem to be of great importance in influencing grain refiner efficiency. The experimental findings are discussed in the context of previously published experimental and theoretical work.
MST/1650
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