The influence of carbon on the phases in the copper-titanium system and their precipitation

The influence of carbon on the phases occurring in the copper-titanium syst em has been experimentally investigated. Samples were fabricated from eleme ntal copper and titanium. Carbon was added in the form of graphite or as ti tanium carbide. The samples were encapsulated, heat-treated at 1173 or 1373 K for 24 h and subsequently quenched in brine. The phases present at the t reatment temperature were identified, as well as the phases occurring durin g solidification. The microstructure indicates the presence of a miscibilit y gap. The composition of the phases were determined using EDS-analysis. Th e composition of the copper phase was found to show a great variation cause d by the precipitation sequence during quenching of the melts. The complex precipitation also caused both TiCu4 and the meta-stable TiCu3 to form. The composition of TiCu was found to show a wider compositional interval than earlier found. The variation of its composition with the nominal compositio n suggests that TiCu can dissolve carbon. The pure Ti phases also showed la rger solubility of copper than earlier found. An outline of the precipitati on sequence is made. (C) 1999 Kluwer Academic Publishers.