| Mechanical activation effects were studied for metal matrix composites (MMC). Planetary mills of high accelerations were applied in super-high energy milling with the aim of obtaining an Aluminium alloy AA6061 containing a finely dispersed hard phase of NiTi or Al2O3. During separate milling of the components it was possible to diminish the particle size and obtain a narrow particle size distribution. The crystallite size attained for Al alloy can be as low as 40 nm. The time of milling in the planetary mills of 28 and 50 g accelerations is much lower than that in the milling devices of lower energy density. During the process of mechanical alloying in the planetary mill further reduction of the crystallite size took place, yielding nanoscale crystallite size for all components. A high degree of coverage of the reinforcement particles by aluminium was achieved. A sample of NiTi mechanically alloyed with AA6061 showed excellent matrix/particle interface and low porosity in the MMC powder. Fine dispersion of NiTi particles was obtained, and the reinforcement particles were well distributed in the matrix. The use of planetary mills of high accelerations can significantly accelerate mechanical alloying. |
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