Temperature effect on the microstructural development of Al-Ni layered binary couples produced by an unconventional method

In this work, the authors have used an unconventional experimental route that consists of (i) deposition of a nickel coating onto an aluminium substrate and (ii) the subsequent heat treatment of created couple in order to produce intermetallic-layered structures, hypereutectic or bulk aluminide intermetallic alloys. The procedure was conducted by controlling chemical concentrations in the Al-rich corner of Al-Ni binary system. The couple was prepared by high velocity oxyfuel spraying of 99.0 wt.% Ni powder onto the surface of 99.999 wt.% Al sheet. The specimens for heat treatment were manufactured immediately after the spraying. The heat treatment was carried out in a differential thermal analysis apparatus by using the temperature range of 600-1200 °C, thus considering the solid state, transient liquid as well as liquid phase of aluminium, with a constant heating/cooling rate of 5 °C/min in an argon atmosphere. Microstructural development of produced alloys was studied by conventional metallography and scanning electron microscopy. Formed intermetallic layers and compounds were evaluated by using energy dispersive microanalysis and image analysis techniques. The development of a novel ultra-fine eutectic alloy is reported.