Solid state reactions in Al-Ni composites made by mechanofusion

Mixtures of aluminium and nickel powders were milled in a Hosokawa AM-15F mechanofusion system in order to produce composite materials with coated or layered microstructure. These composites were then annealed or used in plasma spraying experiments. The intermetallic phases formed in the consecutive steps of the treatment were investigated by means of different methods: electron probe microanalysis (EPMA), transmission electron microscopy (TEM), electron diffraction (ED), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). The-presence of the intermetallic phases confirmed that phase forming solid state reactions start during the mechanofusion treatment. After milling the powder mixture in the Hosokawa equipment, the crystalline Al3Ni could be detected by TEM. A second intermetallic phase, Al3Ni2 was also observed after a heat treatment at 750 K. The microanalytical capabilities of TEM are essential for these investigations. The similarities and the differences between the reactions taking place in the thin films and the thin and/or small milled particles are discussed.