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.
Abstract.Mixtures of aluminium and other metal 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 produced in the consecutive steps of the treatment were investigated by different methods. In the case of the AI-Ni powder system the presence of intermetallic phases confirmed that phase forming solid state reactions start during the first, mechanofusion step. After milling the powder mixture in the Hosokawa equipment, crystalline A13Ni could be detected by TEM. A second intermetallic phase, AI~Ni 2 was also observed after a heat treatment at 750 K. In A1-Cu-Fe and A1-Cu-Co powder composites, produced by milling, binary and ternary phases could be found only after plasma spraying. That means that in these cases the thermodynamic and kinetic requirements of the reactions could not be fulfilled by this mild milling. Nevertheless, the considerably large specific surface of the metal-metal interfaces, formed during the milling process in the ternary composites, makes it possible to produce multi-phase coatings from these composites. It means that only two technological steps are required (milling -plasma spraying). All of the other known technologies consist of three steps: alloy preparation -milling -plasma spraying or alloy preparationatomisation -plasma spraying.Similarities and differences between the reactions taking place in thin films and thin and/or small milled particles are discussed.Key words: A1 alloys, mechanofusion, solid state reactions, intermetallic compounds, QC phases.Mechanical alloying (MA) [1], mechanical milling (MM) and mechanical grinding (MG) are terms, used in the literature for different milling processes, depending on the applied energy, the milling apparatus and the state of the materials to be milled (composition, structure etc.). The phrase mechanofusion (MF) was introduced by Japanese researchers [-2, 3] to describe the process of producing coated powders in a special type of mill. * Dedicated to Professor Dr. rer. nat. Dr. b.c. Hubertus Nickel on the occasion of his 65th birthday ** To whom correspondence should be addressed In order to produce solid state reactions in mixtures of metal powders the mechanical alloying (MA) and mechanofusion processes (MF) can be used. In the course of these treatments the applied mechanical energy is transferred by steel or ceramic balls and/or the moving (rotating) or fixed elements (walls, stator etc.) of the equipment. In consequence of the repeated collisions, the particles are flattened, cold worked, cold welded, crushed, rewelded and dispersed. By the repeated flattening and rewelding of the particles a characteristic layered structure is built up. During these processes the interfaces between the chemically different powders are steadily growing, interdiffusion is going on and new intermetallic phases may develop. As a result of further milling these phases a...
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