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Microstructural Characterization of Cu-Al-Mn-Zn Alloy
Get PDFU okviru ovog diplomskog rada provedena je mikrostrukturna karakterizacija Cu-Al-Mn-Zn legure proizvedene na tri različita načina: taljenjem i lijevanjem u laboratorijskoj elektrolučnoj peći - ingot, postupkom brzog skrućivanja - traka i vertikalnim kontinuiranim lijevanjem - štap. Mikrostrukturna karakterizacija je obuhvaćala optičku mikroskopiju, pretražnu elektronsku mikroskopiju, energijsko disperzijsku spektrometriju, diferencijalno pretražnu kalorimetriju te je provedeno i mjerenje mikrotvrdoće. Sva ispitivanja su provedena na lijevanim i toplinski obrađenim uzorcima (900 °C/30min/voda). Navedena ispitivanja su provedena s ciljem utvrđivanja mogućnosti proizvodnje Cu-Al-Mn legure s prisjetljivosti oblika uz dodatak 3,2% Zn. Optičkom i pretražnom elektronskom mikroskopijom primijećena je prisutnost jednofazne mikrostrukture (α-faza). Energijsko disperzijskom spektrometrijom utvrđena je znatna heterogenost legura. Nakon toplinske obrade uočeno je djelomično poboljšanje homogenosti istraživanih legura. Toplinskom obradom nije se uspjela dobiti martenzitna mikrostruktura, tj. i nakon kaljenja mikrostruktura se sastojala samo od α-faze. DSC analizom određene su temperature egzotermnih i endotermnih pikova na krivuljama zagrijavanja i hlađenja. Mikrotvrdoća Cu-Al-Mn-Zn legure proizvedene u vakuumskoj elektrolučnoj peći je iznosila 685,6 HV10. Nakon toplinske obrade dolazi do znatnog smanjenja mikrotvrdoće legure proizvedene vertikalnim kontinuiranim lijevanjem (517,5 HV10), dok legura proizvedena u vakuumskoj elektrolučnoj peći zadržava približno istu vrijednost mikrotvrdoće (693,6 HV10).Within this graduate thesis the microstructural characterization of Cu-Al-Mn-Zn alloy was performed in three different methods: melting and casting in a laboratory electric arc furnace - ingot, rapid solidification method - ribbon, and with vertical continuous casting - bar. Microstructural characterization included optical microscopy, scanning electron microscopy, energy dispersion spectrometry, differential scanning calorimetry and measurement of microhardness. Investigation was performed on as-cast and heat-treated samples (900 °C/30min/water quenching). The above-mentioned investigations were carried out to determine the possibility of producing Cu-Al-Mn shape memory alloy with the addition of 3.2% Zn. Optical and scanning electron microscopy showed the presence of single phase microstructure (α-phase). Energy dispersion spectrometry determined a considerable heterogeneity of the alloy. After heat treatment, partial improvement of the homogeneity of the investigated alloys was observed. Martensitic microstructure was not obtained by heat treatment, i.e. even after the quenching microstructure consisted of α-phase only. By DSC analysis exothermic and endothermic peak temperatures on heating and cooling curves were determined. Microhardness of Cu-Al-Mn-Zn alloy produced in vacuum electric arc furnace was 685.6 HV10. After heat treatment, a substantial reduction in the microhardness of the alloy produced by vertical continuous casting (517.5 HV10) is achieved, while the alloy
produced in vacuum electric arc furnace retains approximately the same value of microhardness (693.6 HV10)
Influence of Mn on the corrosion behavior of CuAlMn alloy in NaCl solution
Get PDFThe corrosion behavior of different CuAlMn shape memory alloys (Cu-12%Al-4%Mn, Cu-12.3%Al-5.2%-Mn and Cu-12%Al-6%Mn) in 0.9% NaCl solution at pH = 7.4 and T = 37°C was investigated using open circuit potential measurements, polarization and electrochemical impedance spectroscopy methods. It has been found that the corrosion resistance of the tested samples at open circuit potential increases with increasing Mn content in the alloy, i.e. growing in the order of: Cu-12%Al-4% Mn 0.1 V), the corrosion rate increases with Mn content in the alloy, and light microscopy investigations reveal pits on the surface of Cu-12.3%Al-5.2%-Mn and Cu-12%Al-6%Mn alloys, while Cu-12%Al-4%Mn surface is almost clear of any corrosion damage
Effect of phase change materials on heat dissipation of a multiple heat source system
No full textThis paper experimentally investigates heat dissipation of a heat pipe with phase change materials (PCMs) cooling in a multiple heat source system. Two heat sources are fixed at one end of the heat pipe. Considering that a heat sink cannot dissipate all the heat generated by two heat sources, various PCMs are used due to a large latent heat. Different materials in a container are wrapped outside of the middle heat pipe to take away the heat from the evaporation section. The experimental tests obtain temperature data of heat source, evaporation section, and energy storage characteristics of PCMs are also determined under constant and dynamic values of the heat source powers. It is found that under this multiple heat source system structure, the phase change material RT35 maintains temperature variations of the evaporation section at a lower temperature and shortens the required time to reach the equilibrium temperature under a heating power of 20 W
Change of microstructure of Nb microalloyed steel at start of the plastic flow during the cold deformation
No full textMicrostructure has significant impact on the properties and behavior of materials, so it is a subject of intensive investigation nowdays. In this paper, special attention is paid to study on the beginning of the plastic material flow in Nb microalloyed steel during the cold deformation. Specific behavior of this steel can present a significant problem during the metalworking in terms of inhomogeneous deformations appearance. Due to many available methods now it is possible to observe what is happening during the deformation of certain material. Hence, investigation of material flow and stress distribution in deformation zone is growing up today. Therefore, the aim of this work was to establish the change of microstructure of low carbon steel microalloyed with niobium at start of the plastic flow during the cold deformation. For that purpose Nb microalloyed steel was hot rolled into strip and then static tensile test was carried out. Thermography method was used to study the changes of temperature during the deformation. Microstructure before and after deformation was observed by scanning electron microscope. These investigations showed the fine grained ferrite-pearlitic microstructure and its significant changes at start of the plastic flow during the cold deformation
Influence of Niobium Content on Strain Amount in Lüders Bands in Niobium Microalloyed Steel
No full textIn this paper, the influence of niobium content on strain amounts in various areas of Lüders bands propagation was investigated. The tests were simultaneously performed by a static tensile test and a digital image correlation in microalloyed steel with the same base chemical composition but with different addition of 0.035% and 0.06% of niobium. Strain changes were determined by a qualitative and quantitative analysis using a digital image correlation in the area of maximum strain amount behind the Lüders band front (position 1), on the Lüders band front (position 2) and in front of the Lüders band front (position 3). Different deformation behavior of Lüders bands was found in the examined samples with different addition of microalloying element niobium. The area behind the Lüders band front (position 1) showed the highest strain amounts in relation to the other two examined areas. The steel with 0.035% of niobium indicates higher strain amounts in the area of maximum strain behind the Lüders band front (position 1) compared to the steel with 0.06% of niobium which is associated with dislocation density and grain size. This difference is lower on the Lüders band front (position 2) and in front of the Lüders band front (position 3). There were no significant changes in the strain amount with the change of niobium content
Traditional and Modern Carbon Materials
No full textUgljik je osnovni element života na Zemlji, ima veliku obitelj ugljičnih materijala, od tradicionalnih (klasičnih) do suvremenih. Ugljični materijali su materijali sastavljeni od ugljika pri čemu se isključuju spojevi ugljika s drugim elementima. Bez ugljičnih materijala je nezamisliv život današnjeg čovjeka.
Moderniziranim tehnologijama dobivaju se iz nekad tradicionalnih ugljičnih materijala proizvodi koji, zahvaljujući svojim svojstvima, zauzimaju značajno mjesto u suvremenom svijetu.
Ovaj završni rad daje sažet pregled općih svojstava, te postupaka proizvodnje i primjene čađe, metalurškog koksa i naftnog koksa kao tradicionalnih te ugljičnih vlakana, ugljičnih kompozita i grafena kao suvremenih ugljičnih materijala.Carbon is the basic element of life on Earth, has a large family of carbon materials, from traditional (classic) to contemporary. Carbon materials are materials made of carbon, excluding carbon compounds with other elements. Without carbon materials, the life of today´s man is unimaginable.
Modernized technologies are derived from some of the traditional carbon materials products that, thanks to their properties, occupy a worthy place in the modern world.
This work gives a concise overview of general properties and processes for the production and application of carbon black, metallurgical coke and petroleum coke, as traditional, and carbon fibers, carbon composites and graphene as modern carbon materials
Opinion paper about organic trace pollutants in wastewater: Toxicity assessment in a European perspective
Get PDFThis opinion paper focuses on the role of eco- toxicological tools in the assessment of possible impacts of emerging contaminants on the aquatic ecosystem, hence, on human health. Indeed, organic trace pollutants present in raw and treated wastewater are the pivot targets: a multidisciplinary approach allows defining the basic principles for managing this issue, from setting a proper monitoring campaign up to evaluating the optimal process treatment. Giving hints on trace pollutants fate and behavior, attention is focused on the choice of the bioassay( s), by analyzing the meaning of possible biological answers. Data interpretation and exploitation are detailed with the final goal of providing criteria in order to be able to select the best-targeted treatment options. The manuscript deals with conventional and innovative analytical approaches for assessing toxicity, by reviewing laboratory and field assays ; illustrative real scale and laboratory applications integrate and exemplify the proposed approach
Influence of medium on corrosion and microstructural properties of HTCS-130 tool steel for hot work
Get PDFIn this paper the corrosion resistance of tool steel for hot work in the industrial emulsion medium (Lenox Band-Ade semi-synthetic oil + water, in ratio 1:10), water and 3.5% NaCl medium was tested. By Tafel’s extrapolation from polarization curves it was established that the tested tool steel showed extremely high corrosion rate in water and 3.5% NaCl medium in contrast to medium of Lenox BandAde emulsion. The double higher corrosion rate of tool steel is recorded in the chloride medium as opposed to that obtained in water, indicating that the tested steel is more corrosion resistant in water. The obtained results were confirmed by the method of electrochemical impedance spectroscopy. The sample of tool steel in the Lenox Band-Ade emulsion medium showed far greater value of charge transfer resistance Rct than that obtained in the water medium and 3.5% NaCl, which means that the Lenox Band-Ade emulsion formed a thicker oxide layer that has the role of barrier in further penetration of aggressive ions from the solution. The conducted SEM analysis after electrochemical measurements in 3.5% NaCl medium indicate the occurrence of pitting corrosion caused by breaking the passive surface of the material as a result of the action of aggressive ions from the solution. The EDS analysis of formed pits has been shown the increased oxygen content, but also the higher presence of sodium and chlorine, which accumulate in the pits, and come from the medium. Molybdenum and tungsten showed the highest presence in white deposits on the sample surface, which represent parts that did not completely cover with oxide layer, which is why the smallest oxygen content was recorded at these sites. The obtained corrosion rate values in the water medium and the chloride medium indicate that the studied tool steel is poorly stable in water and chloride media, and because of that it can only be used in exceptional cases under conditions in which it will come into contact with water or chloride medium
Evoluation of microstructural and tensile properties of Al-Mg stabs cast with the semi-continuous process
Get PDFU okviru ovog diplomskog rada provedena su ispitivanja na šest aluminijskih blokova aluminijske legure EN AW-5083 lijevanih polukontinuiranim postupkom izravnog hlađenja (eng. Direct Chill). Cilj ovog rada bio je odrediti kako brzina hlađenja, ovisno o položaju uzoraka u bloku, utječe na promjenu broja zrna po jedinici ispitivane površine i vlačna svojstva (vlačnu čvrstoću, granicu razvlačenja i istezanje) lijevanih blokova. U eksperimentalnom dijelu provedena su mjerenjaveličine, tj. broja zrna po jedinici ispitivane površine i vlačnih svojstava na odgovarajućim mjestima unutar poprečno izrezanih ploča s početka i kraja izlivenih blokova. Polazište za određivanje utjecaja brzine hlađenja je statistički plan pokusa („latinski kvadrat“). Ispitivanjem mikrostrukture unutar ispitivanih ploča uočena je nejednolika raspodjela istoosnih zrna, bez pojave stubičastih zrna i transkristalizacijske zone. Iz grafičkih prikaza utjecaja pojedinih varijabli za sve mjerene veličine potvrđen je očekivani utjecaj brzine hlađenja na razvoj i raspodjelu broja zrna čija vrijednost raste od sredine prema svim rubovima blokova što se na isti način manifestira i na promjeni vlačnih svojstava. Statističkom obradom rezultata ustanovilo se da je najznačajniji izvor varijabilnosti visina, odnosnoširina ploče. Relativno visoki koeficijenti korelacije između ploča s početka i kraja ispitivanih blokova (r = 0,66 do 0,77) upućuju na relativno zadovoljavajuću kemijsku, mikrostrukturnu i mehaničku homogenost ispitivanih blokova. Dobiveni rezultati upućuju na relativnu konzistentnost i ponovljivost postupka taljenja, obrade taline i lijevanja blokova aluminijske legure EN AW-5083.Within this thesis six aluminium alloy EN AW-5083 slabs cast with the semi-continuous, vertical direct water cooling process (Direct Chill) have been evaluated. It has been determined how the cooling rate influenced size and number of grains per unit area and tensile properties (tensile strength, yield strength and elongation) of slabs. In the experimental part of this work examinations of microstructural and tensile properties on specified places withing the cross sectioned 300 mm thick place( „slice“ ) on the beginning and the end of the cast slabs were performed. The base for determining influence of the cooling rate was statistical examination plan („latin square“). Microstructure examination in the „slices“ it revealed the unequal distribution of equiaxed grains, without the columnar crystal zone. Graphic figures showed influence of different sources of variability and effect of cooling rates on growth and number of grains distribution. Number of grains grows from center to the rears of ingots. Change of microstructural properties is followed by the change of tensile properties. By statistical processing of obtained results it has been established that the slice height (ingot thickness) is the most significant variability source. Relatively high correlation coefficients between the slices for the beginning and the end of examined ingots for grain numbers and tensile properties (from 0,66 to 0,77) indicate relatively acceptable chemical, microstructural and mechanical homogeneity of the investigated cast slabs. Obtained results reference the relative consistency and repeatability of the melting process, melt treatment and casting of the EN AW-5083 aluminium alloy slabs
Preparation of water for human consumption
Get PDFVoda predstavlja osnovu života na Zemlji. U prirodi kruži u hidrološkom ciklusu između zraka, tla i vodenih tokova (mora, rijeka i jezera). Tijekom hidrološkog ciklusa vrlo često biva zagađena i kao takva nije pogodna za ljudsku potrošnju. Stoga se takva voda mora pripremiti odgovarajućim postupcima.
U ovom radu biti će prikazani najčešći postupci pripreme vode za ljudsku potrošnju kao što su taloženja, koagulacije i flokulacije, filtracije i dezinfekcije.Water represents the basis of life on Earth. In nature it circulates in a hydrological cycle between air, soil and water (sea, river and lake). During the hydrological cycle often becomes contaminated because of which is not suitable for human consumption. Therefore, such water must be prepared by appropriate procedures. This paper presents the most common methods for preparing water for human consumption, such as precipitation, coagulation and flocculation, filtration and disinfection