Phase equilibria and thermodynamic re-assessment of the Cu–Ti system

Abstract

Several as-cast and annealed Cu–Ti alloys were prepared for microstructural, compositional, structural and thermal characterizations. The formation of CuTi2 was congruent and CuTi3 was not found in both as-cast and annealed specimens. The temperatures of nine invariant reactions were determined. The Cu–Ti system was thermodynamically re-assessed according to the experimental phase equilibria and thermochemical properties from this work and the literature. The solution phases Liquid (L), fcc-A1 (Cu), bcc-A2 (βTi) and hcp-A3 (αTi) were treated as substitutional ones. The intermetallics compounds Cu2Ti, Cu3Ti2, Cu4Ti3 and CuTi2 with negligible solubility were described as line ones with the formula CupTiq, while βCu4Ti and CuTi with remarkable solubility were modeled with the formula (Cu,Ti)r(Cu,Ti)s. A group of reliable thermodynamic parameters of the Cu–Ti system were obtained. The calculated results agreed reasonably well with the experimental ones.