Experimental Investigation of Phase Equilibria in the Cu-Cr-Ti System

To provide a basic guide for the design of Cu-Cr-based alloys, phase equilibrium relations in the Cu-Cr-Ti system have been studied using diffusion triples and typical equilibrated alloys. Based on the results from electron-probe microscopy analysis and x-ray diffraction, isothermal sections of the Cu-Cr-Ti ternary system at 1073 and 973 K were constructed, wherein 9 and 11 three-phase equilibria were determined, respectively. A ternary phase with an approximate composition of (Cu, Cr)(4)Ti-3 was detected and named as tau(1). The binary Cu4Ti3 phase does not connect with tau(1) in the ternary region. Solid solution phases (Cu, Cr)(3)Ti-2 and tau(1) were identified and confirmed in both diffusion triple and alloy samples. The solubility of Cr in Cu3Ti2 extends to 12 at.% at both 1073 and 973 K. (Cu, Cr)(3)Ti-2 and Cu3Ti2 form a continuous solid solution at 1073 K while do not exist as one stable phase at 973 K. In addition, two two-phase regions of Cu4Ti + (Cu, Cr)(3)Ti-2 and Cu4Ti3 + (Cu, Cr)(3)Ti-2 transform to the three-phase regions of Cu4Ti + Cu4Ti3 + (Cu, Cr)(3)Ti-2 as the temperature decreases from 1073 to 973 K.