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Impact strength of squeeze casting AlSi13Cu2–CF composite

Zyska A., Konopka Z., Łągiewka M.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 2

49--52

EN

The paper presents the results of research on microstructure and impact strength of AlSi13Cu2 matrix composite reinforced by Ni-coating carbon fibers (CF) with a volume fraction of 5%, 10% and 15%. The composite suspensions were prepared using by stirring method and subsequently squeeze casted under different pressures of 25, 50, 75 and 100 MPa. As part of the study, fiber distribution in aluminum matrix was evaluated and variation in impact strength of composite as a function of the carbon fibers volume fraction and pressure applied were determined. It has been found that the presence of Ni coating on carbon fibers clearly improves their wettability by liquid aluminum alloy and in combination with the stirring parameters applied, composite material with relatively homogeneous structure can be produced. Charpy's test showed that the impact strength of composite reaches the highest value by carrying out the squeeze casting process at 75 MPa. In the next stage of research, it was found that the impact strength of composites increases with the increase of carbon fibers volume fraction and for 15% of fibers is close to 8 J/cm2. Observations of fracture surfaces have revealed that crack growth in the composites propagates with a quasi-cleavage mechanism. During the creation of the fracture, all fibers arranged perpendicular to its surface were sheared. At the same time, the metal matrix around the fibers deformed plastically creating characteristic ductile breaks. The fracture surface formation through the fibers indicates a cohesive and strong connection of the reinforcement with the matrix. In addition to the phenomena mentioned, debonding the fiber-matrix interfaces and the formation of voids between components were observed on the fracture surface.

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The influence of graphite particles on solidification of composite suspension during flow

Konopka Z., Łągiewka M., Zyska A.

Archives of Foundry Engineering

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2007

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Vol. 7, iss. 2

135-138

EN

The measurements concerning the temperature field of the composite suspension with AlMg10 alloy matrix reinforced with graphite particles during its flow in a runner-like mould cavity have been performed for the purpose of investigating the influence of the graphite particles on the solidification kinetics. Applying the derivative differential thermal analysis method, the kinetics of solidification heat release has been calculated for examined composites. The time-dependent quantity of solid phase crystallized over the period of flow has been determined on this basis. The dependence of the solid phase quantity upon the momentary length of the experimental casting has apportioned the length of the solidification zone in the casting and the critical fraction of solid phase at which the flow stops. The solidification zone is longer and the critical fraction of solid phase at the stream front is lower for composite containing 10% of graphite particles than for the one with 20% of graphite. The composite reinforced with 20% of graphite particles flows at a significantly lower rate and exhibits reduced castability as compared with the composite with 10% of graphite. It is caused by the higher solidification rate in the initial stage of the process. The obtained results allow for supposing that graphite particles intensify composite solidification by changing the kinetics of the process.

3

Struktura powierzchni kompozytu AlSi7Mg-SiC po ścieraniu

Mitko M., Tomczyński S.

Kompozyty

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2003

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R. 3, nr 8

363-365

PL

Przedstawiono wyniki badań własności trybologicznych oraz struktury powierzchni roboczych po próbach ścierania kompozytów typu stopu AlSi7Mg-SiC. Kompozyty otrzymano przez odlewanie do kokil ciekłej mieszaniny osnowy metalowej z cząstkami SiC (10% obj.) o frakcji 63-100 mikrometra. W kompozycie osnowa metalowa ściśle przylega do cząstek. SiC, które są w niej rozmieszczone równomiernie (rys. 1). Kompozyt wykazuje znacznie korzystniejsze własności tribologiczne w porównaniu ze stopem swojej osnowy. Zużycie ścierne Zc zmniejsza się o ponad połowę, a współczynnik tarcia suchego f wzrasta o ponad 30% w porównaniu ze stopem osnowy kompozytu (tab. 1). Strukturę powierzchni próbek po ścieraniu oceniano na mikroskopie skaningowym Joel JSM 5400 przy powiększeniach od 35 do 1500 razy (rys. 3). Obecność twardych i o ostrych krawędziach cząstek SiC zwiększa tarcie pomiędzy współpracującymi powierzchniami, energia zużyta, wyrywanie cząstek zbrojących, zarysowywanie i złuszczenia odrywanych fragmentów osnowy metalowej znacznie zwiększa wartość współczynnika tarcia suchego. Natomiast przypowierzchniowe i wystające ponad powierzchnię osnowy twarde cząstki SiC oraz rozkruszone cząstki, wcześniej wyrwane z osnowy, tocząc się pomiędzy współpracującymi powierzchniami, obniżają zużycie ścierne badanego kompozytu.

EN

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-lOO [micro]m size. The metal matrix in the obtained material closely adhere to the particles, which arę 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 nas been examined by means of Joel JSM 5400 scanning electron microscope at magnifications from 35x to 1500x (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.