The structure of a rapidly solidified Al-Fe-Ti-C alloy

Abstract

The microstructures of melt-spun Al-2.03 Fe-0.46 Ti-0.35 C (at %) superheated to 1523 K (ribbon I), and 1673 K (ribbon II), respectively, before quenching, have been characterized using analytical electron microscopy and X-ray diffraction. A duplex microstructure has been observed for ribbon I, consisting of a microcellular region, across a sharp transition, 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 α-Al matrix with an exact orientation relationship. However, the microstructure of ribbon II comprised uniform, fine-scale dispersions of Al₆Fe phase in α-Al grains, and larger size, elongated amorphous phase particles located along the grain boundaries, and approximately 0.46 at % Ti and 0.35 at % C dissolved in the α-Al matrix. During the annealing of ribbon II, the amorphous phase transformed to α_T-AlFeSi phase, the Al₆Fe dispersoids grew upwards and Al₃Fe, TiC particles precipitated in the α-Al matrix. TiC phase formed both in ribbon I and in annealed ribbon II all had an atomic composition of TiC_0.79 (the nominal atomic percent ratio for the alloy $X_C /X_{T_{_j } }$ was 0.74) and a lattice parameter of 0.424 nm. Moreover, there is a cube-cube orientation relationship between TiC and α-Al matrix with a disregistry δ=0.049. In addition, the solidification characteristics of rapid solidification processing (RSP) Al-Fe-Ti-C alloy and mechanism of TiC formation have been discussed.