Experimental investigation on phase equilibria of Cu–Ti–Hf system and performance of Cu(Ti, Hf)2 phase

Phase relations in Cu–Ti–Hf ternary system have been studied by diffusion triple technique supplemented with typical alloy sampling method. Based on results from electron-probe microscopy analysis and X-ray diffraction, isothermal sections of the Cu–Ti–Hf system at 800 and 700 °C were established, which consist of ten and nine three-phase regions, respectively. It is observed that Ti can completely substitute Hf in the CuHf2 phase, indicating formation of a continuous solid solution Cu(Ti,Hf)2. Hf can substitute about 20% Ti in the phase CuTi, while solubility of Ti in Cu10Hf7 and Cu51Hf14 phases reaches to 14 and 11 at.% at 800 °C, respectively. The Cu8Hf3 phase in existence at 800 °C was proved to be unstable at 700 °C. In addition, the elastic modulus and hardness of solid solution Cu(Ti,Hf)2 were determined by using nano-indentation techniques.