Surface microgeometry of aluminium matrix composites after electrodischarge machining
Maria Trzaska*, Dionizy Biało**, Jan Perończyk*** *Politechnika Warszawska, Wydział Inżynierii Materiałowej, ul. Wołoska 141, 02-507 Warszawa **Politechnika Warszawska, Wydział Mechatroniki, Instytut Inżynierii Precyzyjnej i Biomedycznej, ul. św. A. Boboli 8, 02-525 Warszawa ***Politechnika Warszawska, Wydział Inżynierii Produkcji, Instytut Technologii Maszyn, al. Niepodległości 222, 00-663 Warszawa
Annals 4 No. 11, 2004 pages 278-283
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abstract The paper deals with the problems of influence of electrodischarge machining (EDM) on the surface microgeometry of aluminium matrix composites. The composites with Al + 20% Si + 3% Cu + 1% Mg matrix and with particles reinforcing phase Al2O3, SiC and Si3N4 were manufactured from powders in compaction, sintering and hot extrusion processes. Volume fraction of reinforcing phase in composites was 5% (Tab. 1). Generator RLC type was used to perform EDM process (Fig. 1). Kerosene was used as a dielectric. During EDM process different energies of single discharge in the range of 0,044 • 10−3 to 2,268 • 10−3 J (Tab. 2) were utilised. The following parameters were determined: productivity of EDM process and surface roughness Ra. It was shown that energy of the single discharge influences mainly on the EDM process running (Fig. 2). The higher was energy of the single discharge the higher were the productivity of the process and roughness of the composite surfaces. State of the composite surface after EDM was estimated on the base of the scanning microscope images (Figs. 3, 4). It has been noticed that at the material surface after EDM small, solid remelted areas occured. Their dimensions are growing up with increasing of the energy of a single discharge. This phenomenon signifficantly influences on the surface roughness parameters. Moreover the type of the material of reinforcing phase influences the productivity of EDM process (Fig. 2). The speed of machining is the highest for the matrix material. Presence of the electrical non-conductive phases Al2O3 and Si3N4 in the matrix deereases the machining productivity. In the range of EDM process parameters which were used during the investigations, the influence of the type of the reinforcing phase material on surface roughness was not noticed (Fig. 5). Key words: electrodischarge machining, aluminium matrix composite, surface microgeometry