Otpornost na opštu koroziju serije legura cink-aluminijum koje su modifikovane silicijumom i stroncijumom

The resistance to corrosion of the series of zinc-aluminum casting alloys modified with silicon and strontium was studied in a sodium chloride solution. It was shown that general corrosion was the main form of corrosion of Zn25Al-Si-Sr alloys in the test solution. The corrosion process takes place through the anodic dissolution of the alloys, while the cathodic reaction is controlled by diffusion of oxygen in the test solution. Three different electrochemical techniques were applied to determine the corrosion current density, which is the electrochemical indicator of corrosion rate. The value of corrosion current density for each Zn25Al-Si-Sr alloy was calculated using the value of polarization resistance, obtained by electrochemical impedance spectroscopy or by linear polarization resistance technique. The value of corrosion current density was also determined directly from Tafel plots, which were recorded by linear sweep voltammetry. As the content of silicon and strontium in the tested alloys increases, the value of corrosion current density increases gradually. The results obtained by different electrochemical techniques are in good agreementOtpornost na koroziju serije legura cink-aluminijum za livenje, koje su modifikovane silicijumom i stroncijumom, ispitana je u rastvoru natrijum hlorida. Pokazano je da je opšta korozija glavni oblik korozije Zn25Al-Si-Sr legura u navedenom rastvoru. Proces korozije odvija se kao anodno rastvaranje legura, dok je katodna reakcija kontrolisana difuzijom kiseonika u rastvoru. Tri različite elektrohemijske tehnike primenjene su za određivanje gustine struje korozije, koja je elektrohemijski pokazatelj brzine korozije. Vrednost gustine struje korozije za svaku Zn25Al-Si-Sr leguru izračunata je na osnovu vrednosti polarizacione otpornosti, koja je određenai spektroskopijom elektrohemijske impedanse ili tehnikom linearne polarizacije. Vrednost gustine struje korozije je takođe određena direktno iz Tafelovih dijagrama, koji su registrovani pomoću voltametrije sa linearnom promenom potencijala. Sa povećanjem sadržaja silicijuma i stroncijuma u ispitivanim legurama vrednost gustine struje korozije postepeno raste. Rezultati dobijeni različitim elektrohemijskim tehnikama su u dobroj saglasnos

Corrosion behavior of the as-cast and heat-treated ZA27 alloy

Corrosion behaviour of the as-cast and heat-treated ZA27 alloy was examined. The alloy was prepared by conventional melting and casting route and then thermally processed by applying T4 heat treatment regime (solutionizing at 370 °C for 3 hours followed by water quenching and natural aging). Corrosion rate of the as-cast and heat-treated ZA27 alloy was determined in 3.5 wt. % NaCl solution through immersion test using both weight loss method and polarization resistance measurements. It was shown that applied thermal treatment resulted in increased ductility of the heat-treated alloy and had a small beneficial effect on the corrosion resistance of ZA27 alloy

The influence of corrosion on the microstructure of thermally treated ZA27/SiCp composites

The influence of corrosion on the microstructure of ZA27/SiCp composites was examined. The composites were produced by compo casting technique and then subjected to the thermal treatment (T4 regime). Microstructural examinations were performed after 30-day exposure of thermally treated composites in the sodium-chloride solution. Corrosion processes have occurred in the composite matrix. Corrosion did not affect SiC particles in the composites. The local progress of corrosion in depth of the composite matrix was noticed in micro-cracks. Corrosion resistance of ZA27/SiCp composites was evaluated based on the mass loss of composite samples during the immersion test. It was found that corrosion resistance of the composites decreased with increase in content of SiC particles. The applied thermal treatment had a negative influence on the corrosion resistance of ZA27/SiCp composites

Corrosion behavior of compocasted ZA27/SiCp composites in sodium chloride solution

The corrosion behavior of particulate ZA27/SiCp composites in an aerated sodium chloride solution was studied. The composites were synthesized via compocasting with addition of 1, 3 and 5 wt.% SiC particles in the matrix alloy. Composite samples were immersed for 30 days in the 3.5 wt.% NaCl solution open to the atmospheric air. Surface appearance and microstructure of the composites were examined by means of optical microscopy and scanning electron microscopy, while corrosion rates of the composites were determined using the weight loss method. It was revealed that SiC particles were not influenced by corrosion. General uniform corrosion occurred in the composite matrices, mainly in the region of the η phase. Local corrosion was noticed in micro-cracks and near clusters of particulate reinforcements. Results of microstructural examinations and immersion test indicate a slightly lower corrosion resistance of the ZA27/SiCp composites compared to that of the matrix alloy

Tribological behaviour of Al-based MMCs and their application in automotive industry

The use of different kind of composite materials is in constant growing over the years, because they have better physical, mechanical and tribological properties comparing to matrix materials. Composite materials based on light metals like Aluminium, Magnesium and Zinc, due to their low density, find application in many industries. In automotive industry they are used for pistons, cylinders, engine blocks, brakes and power transfer system elements. This paper considers the tribological properties of Al-based MMCs as a function of the manufacturing technologies and variation of shape, dimension and percentage of reinforcement material

Corrosion behavior of compocasted ZA27/SiCp composites in sodium chloride solution

The corrosion behavior of particulate ZA27/SiCp composites in an aerated sodium chloride solution was studied. The composites were synthesized via compocasting with addition of 1, 3 and 5 wt.% SiC particles in the matrix alloy. Composite samples were immersed for 30 days in the 3.5 wt.% NaCl solution open to the atmospheric air. Surface appearance and microstructure of the composites were examined by means of optical microscopy and scanning electron microscopy, while corrosion rates of the composites were determined using the weight loss method. It was revealed that SiC particles were not influenced by corrosion. General uniform corrosion occurred in the composite matrices, mainly in the region of the η phase. Local corrosion was noticed in micro-cracks and near clusters of particulate reinforcements. Results of microstructural examinations and immersion test indicate a slightly lower corrosion resistance of the ZA27/SiCp composites compared to that of the matrix alloy

Corrosion behavior of the as-cast and heat-treated ZA27 alloy

Corrosion behaviour of the as-cast and heat-treated ZA27 alloy was examined. The alloy was prepared by conventional melting and casting route and then thermally processed by applying T4 heat treatment regime (solutionizing at 370 °C for 3 hours followed by water quenching and natural aging). Corrosion rate of the as-cast and heat-treated ZA27 alloy was determined in 3.5 wt. % NaCl solution through immersion test using both weight loss method and polarization resistance measurements. It was shown that applied thermal treatment resulted in increased ductility of the heat-treated alloy and had a small beneficial effect on the corrosion resistance of ZA27 alloy

Tribological behaviour of Al-based MMCs and their application in automotive industry

The use of different kind of composite materials is in constant growing over the years, because they have better physical, mechanical and tribological properties comparing to matrix materials. Composite materials based on light metals like Aluminium, Magnesium and Zinc, due to their low density, find application in many industries. In automotive industry they are used for pistons, cylinders, engine blocks, brakes and power transfer system elements. This paper considers the tribological properties of Al-based MMCs as a function of the manufacturing technologies and variation of shape, dimension and percentage of reinforcement material

Erosive wear properties of ZA-27 alloy-based nanocomposites: Influence of type, amount, and size of nanoparticle reinforcements

Metal matrix nanocomposites (MMnCs) comprise a metal matrix filled with nanosized reinforcements with physical and mechanical properties that are very different from those of the matrix. In ZA-27 alloy-based nanocomposites, the metal matrix provides ductility and toughness, while usually used ceramic reinforcements give high strength and hardness. Tested ZA-27 alloy-based nanocomposites, reinforced with different types (SiC and Al2O3), amounts (0.2 wt.%, 0.3 wt.%, and 0.5 wt.%) and sizes (25 nm, 50 nm, and 100 nm) of nanoparticles were produced through the compocasting process with mechanical alloying pre-processing (ball milling). It was previously shown that the presence of nanoparticles in ZA-27 alloy-based nanocomposites led to the formation of a finer structure in the nanocomposites matrix and an improvement in the basic mechanical properties (hardness and compressive yield strength) through the enhanced dislocation density strengthening mechanism. Solid particle erosive wear testing demonstrated that these improvements were followed with an increase in the erosive wear resistance of tested nanocomposites, as well. Additionally, by analyzing the influences of type, amount, and size of nanoparticles on the erosive wear resistance of nanocomposites, it was demonstrated that there is an optimal amount of nanoparticles, which in our case is 0.3 wt.%, and that the presence of SiC nanoparticles and smaller nanoparticles in nanocomposites had more beneficial influence on erosive wear resistance