Metallic — Intermetallic composites produced by vacuum casting and annealing of Ni and Al

The process of intermetallic layers formation in laminated Ni-Al composite has been investigated. Laminated composite consisting of alternating Ni and Al layers was fabricated by the method of vacuum casting. Ni₂Al₃ and NiAl₃ intermetallic compounds were formed on the Ni-Al interface as a result of subsequent heat treatment. Ni₂Al₃ phase is presented as a continuous layer, intermetallic NiAl₃ exists in eutectic composition with aluminum and as the precipitates of complex shape, which grew deep into the aluminum layer. The amount of NiAl₃ increases when the diffusion occurs in a liquid state (e.g. when the heat treatment temperature was about 720 °C). Optical and SEM microscopy examinations show that Ni₂Al₃ phase has a grain structure, the grain size of Ni₂Al₃ decreases closer to the nickel layer. The lower was the annealing temperature the smaller was Ni₂Al₃ grain size. Intermetallic layers thickness is directly related to the duration and temperature of annealing.