Abstract
A series of Al-Cu-Ni alloys of various compositions were made and annealed at 800°C. The equilibrium phases were studied by metallography, X-ray diffraction (XRD) analysis, and electron probe microanalysis. The isothermal section of the ternary Al-Cu-Ni system at 800°C was then determined based on these experimental results and the available phase relationship knowledge of the three constituent binary systems. No ternary compound was found. All three phases, AlNi 3 , AlNi, and Al 3 Ni 2 , have very high ternary solubility, especially the AlNi phase, which almost reaches the binary Al-Cu side. However, no continuous solid solution was formed between the AlNi phase and any of the binary AlCu phases. Interfacial reactions of Al/Ni, Al/Cu, Al-Cu/Ni, and Al-Ni/Cu at 800°C were investigated by using reaction couple techniques. The results showed that Al 3 Ni and Al 3 Ni 2 phases were formed in the Al/Ni couples; β-AlCu 4 , γ 1 -Al 4 Cu 9 , and ε 2 -Al 2 Cu 3 phases were formed in the Al/Cu couples. As for the results in the Al-2 at. pct Ni/Cu, Al-5 at. pct Ni/Cu, and Al-2 at. pct Cu/Ni, Al-4.5 at. pct Cu/Ni, and Al-6 at. pct Cu/Ni were similar to those in the binary Al/Cu and Al/Ni couples, respectively. A different reaction path was found in the Al-7.5 at. pct Cu/Ni couples, and an AlNi solid solution layer was formed instead of the Al 3 Ni and Al 3 Ni 2 phases.