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Dry sliding wear behaviour of Cu based composite materials reinforced with alumina fibers

Naplocha K., Granat K., Kaczmar J. W.

Archives of Materials Science and Engineering

2013

Vol. 59, nr 2

53--60

Purpose: Parameters for new manufacturing route of Cu casting reinforced with alumina fibers were elaborated. There was observed improvement of hardness and wear properties of composite materials comparing to the unreinforced copper and this indicates for the proper applied process parameters. Design/methodology/approach: Manufacturing of composite materials involves two stages, preparation of porous preforms and next their infiltration with molten Cu. Preforms exhibits semi-oriented arrangement of fibers and their open porosity makes possible the production of composite materials with 10 and 20% by volume of Al2O3 fibers (Saffil). Wear tests were carried out applying the pin-on-disc concept at constant sliding velocity and under two different pressures. Specimens were pressed against the cast iron counterpart prepared from standard brake disc material. Findings: Reinforcing of pure Cu with ceramic fibers results in the significant increase of hardness both by reducing the grain size and creating high level of residual stresses due to thermal mismatch of composite components. Fibers improves effectively wear resistance and under lower pressure of 0.2 MPa, in relation to unreinforced Cu, composite with 20% of fibers exhibits 6 times lower volume lost. Under smaller pressure wear process proceeded with plastic deformation of subsurface, cracking of reinforcement and transferring such segments to friction surface. Wear products containing hard fragments of alumina fibers as well as iron and copper oxides are transferred between surfaces and abrade weared parts. Thus only after friction against composite with 10% of fiber wear of iron counterpart was relatively small. Research limitations/implications: Reinforcing of Cu by squeeze casting method requires application of the die from high temperature resistant steel tool. Preform preheated to high temperature before infiltration, should be transferred to the mold very quickly in order to keep temperature. Practical implications: Reinforced copper , locally reinforced, exhibit high hardness and wear resistance under applied pressures. Production of electronic devices where simultaneously the high thermal and electric conductivity and good wear resistance are required can be potential area of future applications. Originality/value: Investigations are valuable for persons, who are interested in Cu cast composite materials reinforced locally with ceramic fiber performs.

Compression creep of short fibre reinforced magnesium alloy AE42

Dieringa H., Hort N., Kainer K.

Kompozyty

2003

R. 3, nr 7

275-278

Magnesium alloys are gaining increasing interest for automotive applications. Due to their low density and good specific strength cast parts are already in use, such as steering columns, steering wheels or fuel tank covers. Low creep properties at elevated temperatures are limiting applications at temperatures higher than 130°C. Magnesium based mmc's show clearly decreasing creep rates compared to its matrix alloys. In the present paper a 20 vol.-% SaffilŽ short fibre reinforced AE42 magnesium alloy is investigated. Compression creep tests at 200°C with a load of 100 MPa were performed. Creep curves and microstructural changes in the matrix alloy as well as in the mmc are discussed.

Stopy magnezu cieszą się rosnącym zainteresowaniem w motoryzacji. Ze względu na mały ciężar właściwy i dobrą wytrzymałość części odlewane są już stosowane jako kolumny kierownic, koła kierownic czy pokrywy do zbiorników paliwa. Niska odporność na pełzanie w podwyższonych temperaturach ogranicza ich zastosowania w temperaturach wyższych niż 130°C. Tymczasem kompozyty o osnowie metalowej na bazie magnezu wykazują wyraźnie zmniejszone prędkości pełzania w porównaniu ze stopem osnowy. Niniejszy artykuł omawia badania stopu magnezu AE42 zbrojonego krótkimi włóknami SaffilŽ w ilości 20% obj. Przeprowadzono badania pełzania przy ściskaniu w temperaturze 200°C pod obciążeniem 100 MPa. Omówiono krzywe pełzania i zmiany mikrostrukturalne w osnowie oraz w kompozycie.