TI5C4 PHASE-FORMATION IN RAPIDLY SOLIDIFIED AL96.52FE2.03SI0.64TI0.46C0.35 ALLOY

The as-solidified and annealed microstructures of a rapidly solidified Al96.52Fe2.03Si0.64Ti0.46C0.35 alloy were evaluated. The as-solidifie d microstructure comprised an intracellular uniform, fine-scale disper sion of Al6Fe phase in alpha-Al and elongated amorphous particles loca ted along the cell boundaries, with approximately 0.46 at.% Ti and 0.3 5 at.% C saturated in the alpha-Al. During annealing, the amorphous ph ase transformed into alpha(T)-AlFeSi phase, and some of the Al6Fe disp ersoids increased in size while others were replaced by Al3Fe particle s. After annealing at 773 K for 5 h, face centered cubic TiC particles , of approximate atomic composition Ti5C4 and lattice parameter 0.424 nm, precipitated in the alpha-Al matrix. Moreover, there is a cube-cub e orientation relationship between Ti5C4 and the alpha-Al matrix with a disregistry of delta = 0.05. The formation mechanism of this TiC is discussed.