Vpliv vakuumskega taljenja na potek strjevanja elektroliznega aluminija in zlitine AA6082

Prijatelj, Klara (author), Medved, Jože (mentor)

Aluminij je s svojo nizko gostoto, visoko duktilnostjo, dobro korozijsko odpornostjo, visoko toplotno in električno prevodnostjo postal ena od najbolj uporabljenih kovin v zadnjem stoletju. Ko so odkrili industrijski proces za elektrolizno redukcijo aluminijevega oksida v čisti aluminij, se je uporaba aluminija močno povečala. Od takrat nas aluminij spremlja v vsakodnevnem življenju in včasih se niti ne zavedamo, da je prisoten. Elektrolizni aluminij čistosti 99,7 mas. % spada v skupino aluminijevih zlitin 1XXX in ima dobro korozijsko odpornost. Aluminijeva zlitina AA6082, ki spada v skupino 6XXX, je srednje trdna zlitina, ima odlično korozijsko odpornost in se uporablja v raznih aplikacijah. Namen diplomskega dela je bil ugotoviti vpliv taljenja v vakuumu na potek strjevanja elektroliznega aluminija in zlitine AA6082 v primerjavi z rezultati taljenja in litja na zraku. Za taljenje smo uporabili vakuumsko indukcijo peč, za preiskave pa smo uporabili rentgensko fluorescenčno analizo (XRF), enostavno termično analizo (ETA) ter diferenčno vrstično kalorimetrijo (DSC). Po opravljenih analizah smo primerjali ohlajevalne krivulje posameznih zlitin ter ogrevalne in ohlajevalne DSC krivulje. Ugotovili smo, da sta vzorca, ulita v vakuumu, potrebovala skoraj dvakrat več časa za strjevanje ter, da je bila ohlajevalna hitrost manjša, kot pri vzorcih, ki smo jih ulili na zraku. Opazimo tudi, da so temperature likvidus in solidus višje pri vzorcih, ki se strjujejo v vakuumu, kot pri vzorcih ulitih na zraku. Z DSC analizo zlitine AA1070 smo zaznali premenske temperature faz Al13Fe4 ter primarnih zmesnih kristalov αAl. Pri zlitini AA6082 smo zaznali premenske temperature faz Al18Fe2Mg7Si10, Mg2Si, Al15Si2Mn4 ter primarnih zmesnih kristalov αAl. Ugotovili smo, da se več entalpije porabi ter sprosti pri obeh zlitinah, ki smo ju ulili v vakuumu.

• Language: Slovenian
• Keywords: Zlitina AA1070, zlitina AA6082, taljenje in litje v vakuumu, enostavna termična analiza, DSC
• Work type: Bachelor thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2018
• PID: 20.500.12556/RUL-101829
• COBISS.SI-ID: 1736287
• Publication date in RUL: 08.07.2018

Secondary language

• Language: English
• Title: Influence of vacuum melting on the solidification path of primary aluminium and AA 6082 alloy

Abstract

With low density, high ductility, good corrosion resistance, high thermal and electrical conductivity, aluminium has become one of the most frequently used metal in the last century. When the industrial process for the electrolysis reduction of aluminium oxide in pure aluminium was discovered, the use of aluminium increased significantly. Since then, aluminium has been following us in everyday life and sometimes we are not even aware of its presence. Electrolysis aluminium of 99.7 wt. % purity belongs to the group of aluminium alloys 1XXX and it has good corrosion resistance. Aluminium alloy AA6082, which belongs to the group 6XXX, is a medium hard alloy, has excellent corrosion resistance and is used in various applications. The purpose of the diploma work was to determine the influence of melting in vacuum on the course of solidification of electrolysis aluminium and alloy AA6082 compared to the results of melting and casting in the air. We used vacuum induction furnace for melting and X-ray fluorescence analysis (XRF), simple thermal analysis (ETA) and differential scanning calorimetry (DSC) for the investigations. After analyses we compared the cooling curves of individual alloys and the heating and cooling DSC curves. We found that the samples, cast in vacuum, needed almost twice as much time for solidification and that the cooling rate was lower than in the samples we poured in the air. It is also observed that the liquidus and solidus temperature is higher at the samples cast in vacuum than in samples cast in air. By DSC analysis of the AA1070 alloy we detected the transformation temperatures of the phases Al13Fe4 and the primary crystals of αAl. At alloy AA6082 we detected the transformation temperatures of the phases Al18Fe2Mg7Si10, Mg2Si, Al15Si2Mn4 and primary crystals of αAl. We have found that more enthalpy is consumed and released at two alloys that were cast and solidified in vacuum.

• Keywords: Alloy AA1070, alloy AA6082, melting and casting in vacuum, simple thermal analysis, DSC