Production of composite 2024 Al-SiC and 6060 Al-SiC powders by the mechanical alloying
Jacek W. Kaczmar, Adam Kurzawa, Andrzej Janus Politechnika Wrocławska, Instytut Technologii Maszyn i Automatyzacji, ul. Łukasiewicza 3/5, 50-371 Wrocław
Quarterly No. 4, 2005 pages 61-66
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abstract Investigations of production of composite 2024 Al+SiC and 6060 Al+SiC composite powders based on Mechanical Alloying process are presented in the paper. Mechanical Alloying process, it is the high energy milling of soft matrix metal powders with the hard particles of the strengthening phase in the high energy ball mill-attritor. In the milling process the composite powder with particles composed of matrix material and strengthening particles of micron and submicron diameters are produced. Composite powders produced by mechanical alloying process are applied for further production of composite materials and elements. In order to produce the composite elements the processes of powder metallurgy are applied - pressing and sintering and cold and hot plastic processing - extrusion and forging. For production of composite powders containing 5, 10 and 15 vol.% of silicon carbide SiC characterized by powder mean diameters of 3 μm in the soft matrix powders of 2024 Al and 6060 Al, the attritor with the vertical rotor was applied. The goal of the investigations was to determine the milling time for the production of composite Al-SiC powders characterized by the homogeneous distribution of strengthening SiC powders in the matrix. For this purpose the powders were milled applying different milling times (t1 = 0.5, t2 = 1, t3 = 2 hours) and of rotor different rotation velocities (v1 = 90, v2 = 120 1/min). Microscopic investigations allowed to determine the stages of composite Al-SiC powders forming as the result of the sequential deformations of matrix powders by steel balls agitated by the rotor (Figs 2-4). The statistical evaluation of the distribution homogeneity of the SiC particles in the aluminium alloyed powders was performed determining the: variances σ2 for mean interparticle spacings, confidence intervals from the real mean interparticle spacings λ śr for 1 – α = 0.95 and the homogeneity coefficients ξ of SiC particles distribution. Statistical analysis has shown the effect of the milling time and milling rotation velocity as well as the relative volumetric content of SiC strengthening particles in the matrix on the process of composite Al-SiC particles forming and for achieving of homogeneous distribution of SiC particles in the matrices of 2024 Al and 6060 Al. Key words: Al-SiC composite materials, composite powders, mechanical alloying