Effect of Magnesium Addition on the Cell Structure of Foams Produced From Re-melted Aluminum Alloy Scrap

Closed-cell foams were produced from re-melted aluminum alloy scrap that contained 0.13 wt pct Mg magnesium in the as-received state and higher levels after adding 1, 2, or 5 wt pct Mg. The excess Mg gave rise to the fragmentation of long oxide filaments present in the scrap alloy into smaller filaments and improved its distribution and wetting by the Al matrix. Foaming the re-melted scrap alloy containing 1, 2, and 5 wt pct Mg excess showed stability and good expansion in comparison to the scrap alloy containing 0.13 wt pct Mg only, but the cells became non-equiaxed when the Mg concentration was high (≥2 wt pct excess) due to cell wall rupture during solidification. Compressibility and energy absorption behavior were studied for scrap alloy foams containing 1 wt pct Mg excess, which is the optimum level to obtain good expansion, stability, and uniform cell size. Foams with densities in the range of 0.2 to 0.4 g cm−1 produced by holding at the foaming temperature for different times were used for the investigation. A uniform cell structure led to flatter stress plateaus, higher energy absorption efficiencies, and reduced “knockdown” in strength compared with commercial foams made by gas bubbling. The mechanical performance found is comparable to that of commercial foams made by a similar method but the expected costs are lower

Tribological characterization of high porosity aluminum based composite materials

The present work aims to study the effect of the reinforcing phase on dynamic coefficient of friction and mass wear of specimen with different compositions under various friction conditions. Porous materials with different compositions and reinforcing phase are obtained by replication method applying salt (NaCl) space holder. The reinforcing phase is Fly Ash (FA) particles. The microstructure of the obtained materials is observed and the tribological properties such as mass losses and the dynamic coefficient of friction are determined. A comparison of the tribological properties between nominally nonporous matrix, porous matrix and porous composite are presented in this study

Prace studialne nad teoretycznymi i praktycznymi aspektami projektowania materiałów lżejszych od powietrza

This paper discusses some theoretical aspects of the design of ultralight materials. Potential application of syntactic foams in the fabrication of composites lighter than air is also analyzed. Carbon allotropic forms (fullerenes, colossal carbon tubes) and some non-carbon matters are considered as components of ultralight composites. Calculations for the size of fullerenes, the number of carbon atoms in their structure and thickness of reinforcing phase are presented. It is concluded that 3D carbon molecules (fullerenes) and colossal carbon tubes are the most promising components for design of ultralight metallic materials which can be lighter than air.W artykule omówiono wybrane teoretyczne aspekty projektowania ultralekkich materiałów kompozytowych. Przeanalizowano potencjalne zastosowanie pian syntektycznych w produkcji kompozytów lżejszych od powietrza. Uwzględniono alotropowe odmiany węgla (fulereny, "kolosalne" nanorurki węglowe), jak również niektóre substancje niewęglowe mogące znaleźć zastosowanie jako komponenty ultralekkich kompozytów. Podano wzory, które pozwalają obliczyć wielkość fulerenów, liczbę atomów węgla w ich strukturze i grubość ścianek fazy zbrojącej. Stwierdzono, że cząsteczki węgla 3D (fulereny) i nanorurki węgla o makrorozmiarach stanowią najbardziej obiecujące substancje do projektowania ultralekkich materiałów o gęstości mniejszej od gęstości powietrza

Sterowanie strukturą w hipotetycznych gazarach gradientowych

Development of instruments for micro- and macrostructure design in functionally graded materials is a challenge for the modern industry. In this path, mathematical modeling and numerical simulation are extremely helpful techniques for design and investigations of functionally graded materials. The aim of this paper is to show the possibility for production of gasars with graded porous structure. This is done by means of comprehensive mathematical model of fered by the authors in a previous work. The way to control the structure by means of processing parameters is discussed on the basis numerical experiments related to copper/hydrogen system.Rozwój metod projektowania mikro- i projektowanie makrostruktury materiałów określanych mianem funkcjonalnych gradientowo stanowi wyzwanie dla nowoczesnego przemysłu. Modelowanie matematyczne i symulacja numeryczna są technikami niezmiernie pomocnymi w zakresie wyznaczania wytycznych technologicznych dla opracowania i przewidywania właściwości danej klasy materiałów. Celem danej pracy jest analiza możliwości wytwarzania nowego rodzaju materiałów - hipotetycznych gazarów - charakteryzujących się gradientową strukturą porowatą. Opierając się na wynikach poprzednich praca autorów, zaproponowano model matematyczny, umożliwiający sterowanie strukturą mediów porowatych o ukierunkowanej strukturze por. Poczynione założenia przedyskutowano na podstawie numerycznych eksperymentów dotyczących układu miedź - wodór. Stwierdzono, że podstawowymi parametrami technologicznymi procesu wytwarzania gazarów o strukturze gradientowej jest parcjalne ciśnienie gazu, wywierane na ciekły metal przed i w trakcie krzepnięcia. Zmiana ciśnienia prowadzi do zasadniczych zmian w ilości zarodków i por w odniesieniu do jednostki powierzchni. Uzyskiwana porowatość może się wahać w szerokim zakresie 0-40%, co pozwala na wytworzenie materiału o wysokim gradiencie właściwości

High porosity fly ash/Ni/P composite produced by electroless deposition

The aim of the present study is to create a composite material possessing useful properties enabling the waste fly ash to be utilized. To obtain the final material, fly ash is subjected to separation by size and density. The innovative approach to making the composite material is the use of chemical nickel deposition by which the free particles are bonded as a solid body. Deposition of nickel was carried out by two stages: first Ni-coating of the particles and second – bonding of the particles by nickel deposition. Structure of this material is near to syntactic foam. Some properties of the obtained material as a porosity, density, and permeability with regard to its application have been investigated

Tribological Characterization of Aluminum/Babbitt Composites and Their Application to Sliding Bearing

The present work studies the tribological properties of new hybrid material composed from high porosity open cell aluminum alloy (AlSi10Mg) skeleton and B83 babbitt infiltrated into it. The porous skeleton is obtained by replication method applying salt (NaCl) as space holder. The reinforcing phase of the skeleton consists of Al2O3 particles. The skeleton contains Al2O3 particles as reinforcement. The microstructure of the obtained materials is observed and the tribological properties are determined. A comparison between tribological properties of nominally nonporous aluminum alloy, high porosity open cell skeleton, babbitt alloy and the hybrid material is presented. It is concluded that new hybrid material has high wear resistivity and is a promising material for sliding bearings and other machine elements with high wear resistivity