Phase equilibria of the Cu-Nb-Ti system at 850 °C

The phase equilibria of the Cu-Nb-Ti system at 850 °C were investigated by a high-efficiency diffusion couple approach. The samples were studied by means of optical microscopy, scanning electron microscopy and electron probe microanalysis. At 850 °C, the phase TiCu2, the stability range of which is controversial in the literature, was observed. The solubilities of Nb in Ti2Cu, TiCu and Ti3Cu4 were determined to be 3.5, 3.1 and 4.6 at.%, respectively. The solubility of Nb in TiCu4 was negligibly small. The following three-phase equilibria were observed: Ti2Cu + TiCu + (Nb,Ti), TiCu + Ti3Cu4 + (Nb,Ti) and Ti3Cu4 + TiCu4 + (Nb,Ti).