Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Patryk Wrześniowski"

The interaction characteristics of liquid magnesium and selected magnesium alloys with open-celled glassy carbon foams DOI:10.15199/28.2018.2.3

  1. INTRODUCTION In the last decades, the developments in the technologies of carbon materials have caused new products usable as components in composite materials. In that group, we can find carbon fibers, glassycarbon particles, carbon nanotubes and graphene. At first, they were extremely expensive, but with time, they became cheaper and can be now commercially applied. Among the carbon materials, a new one has appeared, i.e. the glassy carbon open-celled foams (Cof), which, so far, have found applications as a sound absorption material, a biomaterial, a catalyst support or a thermal management material [1÷4]. The Cof are built of cells with walls containing windows and their geometry is commercially characterized by ppi (pores per inch), which means that the pore size increases with a ppi decrease [3, 5÷7]. That type of macrostructure gives the opportunity for carbon foams to be infiltrated by liquid media and to form interpenetrating phase composites [7÷9]. The research works focused on metal matrix composites report that continuous carbon fibers can be infiltrated by magnesium alloys, and magnesium matrix composites with dispersed carbon reinforcements as short fibers, particles and nanotubes can be processed by different powder technologies and casting methods [10÷16]. However, the results of wettability measurements are not unequivocal. If the equilibrium contact angle θ is less than 90°(socalled “good wettability state"), a spontaneous infiltration of molten magnesium into the porous fibres and open-celled preforms can be expected. The contact angle θ between the molten magnesium and the porous graphite as well as the vitreous carbon determined by Shi et al. [17] by the sessile drop method at 700°C in a chamber filled with argon and magnesium vapor was 80° and 74°, respectively. However, the works of other authors [18÷21] showed values higher than 90° as well as poor wettability. The contact angle estima[...]

Wear resistance of composites with Mg-Zn-RE-Zr alloy matrix and open-celled carbon foam DOI:10.15199/28.2019.2.3

  1. INTRODUCTION Magnesium and its alloys are currently used in the automotive industry for such parts as an inner door, tailgate, steering wheel core and column, seat frame, or wheel rims [1, 2]. Recent studies on development of magnesium alloys and magnesium matrix composites have focused on energy saving, weight reduction, and limiting environmental impact [2]. Nowadays, most magnesium components in the automotive industry are made of AM alloys (e.g.: inner door manufactured from AM50 alloy) or AZ alloys (e.g.: supports manufactured from AZ91D alloy). It was reported that some BMW engine blocks were also produced from magnesium alloys (six-cylinder inline combustion engine made from AJ62 alloy [2]). Magnesium-aluminium alloys can be characterized by good castability [2÷4], because of that, they can be applied in a high-pressure die casting (HPDC) process [1÷4]. However, creep properties of those alloys are lower than magnesium alloys containing rare earth elements (RE), because of that, that type of alloy is more often applied for wheel rims or gearboxes. Because of zirconium presence (applied in order to grain refinement [5]), those alloys can be sand casted [6, 7]. Wear properties are especially important when magnesium alloys are applied for critical automobile parts such as air intake, transmission, or suspension system [8÷11]. Literature shows that reinforcing magnesium matrix composites with glassy carbon particles (Gcp) or short carbon fibers (Csf) improves wear resistance of composites [12÷15], while some decrease of density was noticed [13÷15]. However, application of particles or short fibers as reinforcement can cause technological problems because of stability loss by Mg-C suspension, related to differences in components densities [16]. The segregation of carbon reinforcement in composite occurs in the form of two zones: Gcp - a rich zone (top of suspension, effect of less Gcp density) and an α-Mg zone. App[...]

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