diplomsko delo
Domen Nussdorfer (Author), Jože Medved (Mentor)

Abstract

Aluminij je tretji najpogostejši element in najpogostejša kovina v zemeljski skorji. Je mehka lahka kovina srebrnobele barve z zelo dobrimi metalurškimi lastnostmi, kot so npr. odpornost proti koroziji, majhna gostota, električna prevodnost, žilavost in nemagnetnost. Aluminijeve zlitine imajo bistveno boljše mehanske lastnosti kot primarni aluminij. Zato pogosto nadomeščajo materiale, kot so plastika, les, jeklo, baker ... in so zelo popularne v industriji vozil, gradbeništvu, elektrotehniki, gospodinjstvu ... Odpadni aluminij, ki ga porabniki zavržejo, zbiramo in shranjujemo na deponijah, kjer ga kasneje predelajo oziroma reciklirajo. Reciklaža aluminija je proces, ki omogoča odpadni aluminij ponovno uporabiti za izdelavo novih izdelkov. Aluminij lahko recikliramo večkrat, ne da bi izgubil svoje lastnosti, zato so stroški pri predelavi sekundarnih surovin bistveno manjši, saj porabimo le približno 5 % energije, ki je potrebna za pridobivanje primarnega aluminija iz boksita. Predelava aluminijevih sekundarnih surovin sestoji iz priprave surovin, sortiranja, taljenja, legiranja, obdelave taline, čiščenja taline in litja. Namen diplomskega dela je bil ugotoviti vpliv specifične površine sekundarnega aluminija na lastnosti taline zlitine EN AW 5182. Obravnavana zlitina spada v skupino aluminijevih zlitin 5XXX, katerih glavni legirni element je magnezij. Je dobro korozijsko obstojna in ima dobre mehanske lastnosti. Za preiskavo izdelanih zlitin smo uporabili: enostavno termično analizo (ETA), rentgensko fluorescenčno analizo (XRF), diferenčno vrstično kalorimetrijo (DSC), termodinamsko modeliranje zlitin (Thermo-Calc) in vrstični elektronski mikroskop (SEM) z energijsko disperzijskim spektrometrom (EDS). S pomočjo termodinamičnega izračuna smo predvideli, katere faze se lahko pojavljajo v mikrostrukturi in kako nanje vpliva velikost specifične površine dodanega sekundarnega materiala. S pomočjo enostavne termične analize smo izrisali ohlajevalne krivulje vseh petih zlitin in določili njihove karakteristične točke. Iz rezultatov sklepamo, da se z dodajanjem sekundarnega materiala zmanjšuje talilna entalpija. Z materialom, ki ima veliko specifično površino, vnesemo v talino več nečistoč kot z materialom z majhno specifično površino. Nečistoče pa v talini znižajo temperature karakterističnih točk in posledično je potrebne manj energije za taljenje. Iz slik mikrostruktur, posnetih z vrstičnim elektronskim mikroskopom, smo identificirali in primerjali dobljene faze, določene z energijsko disperzijskim spektometrom, s fazami, ki smo jih dobili iz termodinamičnega izračuna.

Keywords

aluminijeva zlitina EN AW 5182;reciklaža;specifična površina;enostavna termična analiza;diferenčna vrstična kalorimetrija;termodinamika;

Data

Language: Slovenian
Year of publishing:
Typology: 2.11 - Undergraduate Thesis
Organization: UL NTF - Faculty of Natural Sciences and Engineering
Publisher: [D. Nussdorfer]
UDC: 669
COBISS: 148017667 Link will open in a new window
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Downloads: 3
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Other data

Secondary language: English
Secondary title: influence of specific surface of secondary raw materials of EN AW 5182 alloy on melt quality
Secondary abstract: Aluminium is the third most common element and the most common metal in the Earth's crust. It is a soft, light, silvery-white metal with very good metallurgical properties, such as corrosion resistance, low density, electrical conductivity, toughness and non-magnetism. Aluminium alloys have significantly better mechanical properties than primary aluminium. Therefore, they often replace materials such as plastic, wood, steel, copper, etc., and are very popular in the automotive industry, construction, electrical engineering, households and so on. Aluminium scrap that consumers throw away is collected and sent to landfills, where it is later processed or recycled. Aluminium recycling is a process by which aluminium scrap can be reused to make new products. Aluminium can be recycled many times without losing its properties, so the cost of processing secondary raw materials is much lower, because we use only about 5% of the energy required to extract primary aluminium from bauxite. Processing of aluminium scrap includes preparation of the raw material, sorting, melting, alloying, melt treatment, cleaning of the melt and casting. The aim of the thesis was to determine the influence of the specific surface area of secondary aluminium on the melt properties of the alloy EN AW 5182. The considered alloy belongs to the 5XXX series aluminium alloys, the main alloying element is magnesium. It exhibits good corrosion resistance and good mechanical properties. The following were used to study the alloys produced: simple thermal analysis (ETA), X-ray fluorescence analysis (XRF), differential scanning calorimetry (DSC), thermodynamic modeling of the alloy (Thermo-Calc) and a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS). Using thermodynamic calculations, we predicted which phases may occur in the microstructure and how they are affected by the size of the specific surface area of the added secondary material. Using a simple thermal analysis, we plotted the cooling curves of all five alloys and determined their characteristic points. From the results, we conclude that the addition of secondary material decreases the enthalpy of reaction, so that less energy is expended for melting. For a material with a large specific surface area, more impurities are introduced into the melt than for a material with a small specific surface area. However, the impurities in the melt lower the temperatures of the characteristic points, so less energy is required for melting. Using images of the microstructures taken with a scanning electron microscope, we identified the phases determined with an energy dispersive spectrometer and compared them with those obtained from thermodynamic calculations.
Secondary keywords: aluminium alloy EN AW 5182;recycling;specific surface area;simple thermal analysis;differential scanning calorimetry;thermodynamics;
Type (COBISS): Bachelor thesis/paper
Study programme: 0
Thesis comment: Univ. v Ljubljani, Naravoslovnotehniška fak., Oddelek za materiale in metalurgijo
Pages: XIX, 54 str.
ID: 18509038