THE STRUCTURE OF A RAPIDLY SOLIDIFIED AL-FE-TI-C ALLOY

The microstructures of melt-spun Al-2.03 Fe-0.46 Ti-0.35 C (at %) supe rheated to 1523 K (ribbon I), and 1673 K (ribbon II), respectively, be fore quenching, have been characterized using analytical electron micr oscopy and X-ray diffraction. A duplex microstructure has been observe d for ribbon I, consisting of a microcellular region, across a sharp t ransition, followed by a coarser cellular or dendritic structure. The intercellular phases consisted mostly of Al6Fe (few of Al3Fe) and the dispersed TiC particles distributed in the alpha-Al matrix with an exa ct orientation relationship. However, the microstructure of ribbon II comprised uniform, fine-scale dispersions of Al6Fe phase in alpha-Al g rains, and larger size, elongated amorphous phase particles located al ong the grain boundaries, and approximately 0.46 at % ii and 0.35 at % C dissolved in the alpha-Al matrix. During the annealing of ribbon II , the amorphous phase transformed to alpha(1)-AlFeSi phase, the AI,Fe dispersoids grew upwards and Al3Fe, TiC particles precipitated in the alpha-Al matrix. TiC phase formed both in ribbon I and in annealed rib bon II all had an atomic composition of TiC0.79 (the nominal atomic pe rcent ratio for the alloy X(c)/X(Ti) was 0.74) and a lattice parameter of 0.424 nm. Moreover, there is a cube-cube orientation relationship between TiC and alpha-Al matrix with a disregistry delta = 0.049. In a ddition, the solidification characteristics of rapid solidification pr ocessing (RSP) Al-Fe-Ti-C alloy and mechanism of TiC formation have be en discussed.