The surface structure of the AlSi7Mg-SiC composite after abrasion test
Marian Mitko, Szczepan Tomczyński Politechnika Częstochowska, Katedra Odlewnictwa, al. Armii Krajowej 19, 42-200 Częstochowa
Annals 3 No. 8, 2003 pages 363-365
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abstract The paper presents the results of tribological examinations, as well as the examinations of the working surface structure after abrasion tests performed for the AlSi7Mg/SiC composite. The composite has been obtained by die-casting of the mixture of the liquid metal matrix and SiC particles (10 vol.%) of 63÷100 μm size. The metal matrix in the obtained material closely adhere to the particles, which are evenly distributed in its volume (Fig. 1). The composite exhibits much more advantageous tribological properties than the matrix itself. The abrasive wear Zc is reduced by over a half, and the coefficient of dry friction f increases by over 30% as compared with the pure matrix alloy (Table 1). The structure of the specimens surface after abrasion test has been examined by means of Joel JSM 5400 scanning electron microscope at magnifications from 35× to 1500× (Fig. 3). The presence of hard SiC particles of sharp edges increases friction between the mating surfaces, and the energy expenditure due to scratching and spalling of the metal matrix, and pulling out the reinforcing particles significantly increases the value of the coefficient of dry friction. On the other hand, the surface-close hard SiC particles, projecting from the matrix surface, and the crushed particles formerly pulled out from the matrix and rolling between the co-operating surfaces decrease the abrasive wear of the investigated composite. Key words: casting, casting composites, tribological properties