Fabrication of in situ TiC reinforced aluminum matrix composites Part I: Microstructural characterization

Abstract

In the present work traditional ingot metallurgy plus rapid solidification techniques were used to in situ produce Al-TiC composites with refined microstructures and enhanced dispersion hardening of the reinforcing phases. Microstructural characterization of the experimental materials were comprehensively done by optical, electron microscopy and X-ray diffraction. The results show that the in situ synthesized TiC particles possess a metastable fcc crystal structure with an atomic composition of TiC08 and a lattice parameter of 0.431 nm. The typical ingot metallurgy microstructures exhibit aggregates of TiC particle phase segregated generally at the α-Al subgrain or grain boundaries and consisted of fine particles of 0.2–1.0 μm. After re-melting of the ingots and hence rapid solidification, the microstructures formed under certain thermal history conditions contained uniform fine-scale dispersion of TiC phase particles with a size range of 40–80 nm in an Al supersaturated matrix of 0.30–0.85 μm grain size. In the most case these dispersed TiC particles have a semi-coherent relationship with the α-Al matrix.