Mikrostruktura posebnih bakrovih zlitin, izdelanih iz recikliranega materiala : magistrsko delo

Kresnik, Žan (author), Naglič, Iztok (mentor), Resnik, Andrej (comentor)

Kalupi za steklarsko industrijo se pogosto izdelujejo iz posebnih bakrovih zlitin, ki imajo odlično toplotno prevodnost in odpornost proti toplotni utrujenosti. Na najbolj obremenjenih mestih se na kalupe navarijo nikljeve ploščice ali vstavijo nikljevi vstavki, ki se prelijejo s talino. Po uporabi se izrabljeni kalupi v celoti reciklirajo in ponovno izdelajo s procesom ulivanja. V magistrskem delu smo karakterizirali mikrostrukturo petih vzorcev, izdelanih iz posebne bakrove zlitine (z interno oznako OMX), ki vsebuje 15-16,5 mas. % Ni, 9,5-10 mas. % Al, 7,5-9 mas. % Zn in do 1,25 mas. % Fe, pri čemer smo se osredotočili predvsem na nečistoče. Pri dveh kalupih, z navarjeno ploščico in zalitim vstavkom, smo analizirali tudi mikrostrukturi obeh nikljevih zlitin ter njunih spojev z osnovno bakrovo zlitino. Njuna karakterizacija je dodatno pojasnila vir nečistoč v bakrovih zlitinah OMX. Pri karakterizaciji so bile uporabljene metode svetlobne mikroskopije (LM), vrstične elektronske mikroskopije (SEM), energijsko disperzijske spektroskopije (EDS) in rentgenske fazne analize (XRD). Mikrostruktura vzorcev iz zlitine OMX je sestavljena iz enakoosnih dendritov primarne faze ß-AlNi, v vmesnem območju med dendriti pa se nahaja evtektski zlog (?Cu + ß-AlNi). Vzorci so vsebovali tudi precej nečistoč, zlasti boridov, bogatih s kromom in železom, pojavljali pa so se še razvejani kompleksni oksidi in svinec. Ugotovili smo, da količina železa v boridih znatno vpliva na njihovo obliko. Kemijska sestava in posledično mikrostruktura ploščic ter vstavkov se zelo razlikuje. Ugotovili smo, da na spoju med ploščico in osnovno bakrovo zlitino nastanejo boridi, ki se nato pojavljajo v zlitinah OMX. Spoj med vstavkom in bakrovo zlitino pa je vseboval več razvejanih oksidov na osnovi aluminija, kakršni se pojavljajo tudi v mikrostrukturi ulitkov iz bakrove zlitine OMX.

• Language: Slovenian
• Keywords: posebne bakrove zlitine, nikelj, boridi, karakterizacija mikrostrukture, vrstična elektronska mikroskopija, energijsko disperzijska spektroskopija
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: [Ž. Kresnik]
• Year: 2021
• Number of pages: XVI, 64 f.
• PID: 20.500.12556/RUL-131357
• UDC: 669
• COBISS.SI-ID: 84883459
• Publication date in RUL: 25.09.2021

KRESNIK, Žan, 2021, Mikrostruktura posebnih bakrovih zlitin, izdelanih iz recikliranega materiala : magistrsko delo [online]. Master’s thesis. Ljubljana : Ž. Kresnik. [Accessed 21 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=131357

Secondary language

• Language: English
• Title: Microstructure of special copper alloys produced from recycled material : master's thesis

Abstract

Molds for the glass industry can be made from special copper alloys that have excellent thermal conductivity and resistance to thermal fatigue. Nickel plates are welded or nickel inserts are engulfed by a molten alloy at the most structurally critical points of the molds. At the end of their service life, the used molds are recycled together with the nickel plates and inserts. The aim of the master’s thesis was to characterize the microstructure of five samples of the special copper alloy OMX containing 15-16,5 wt. % Ni, 9,5-10 wt. % Al, 7,5-9 wt. % Zn and up to 1,25 wt. % Fe, focusing on impurities. The microstructure of nickel plate and nickel insert and their joints with a special copper alloy were also investigated to further explain the source of impurities in OMX alloys. Characterization methods used in this work include optical microscopy (LE), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The microstructure of the OMX special copper alloy samples consists of equiaxed dendrites of primary phase β-AlNi and eutectic (αCu + β-AlNi). The samples also contained several impurities, especially chromium and iron rich borides, while complex oxides and lead were also found very frequently. The amount of iron in the borides was found to significantly affect their shape. The chemical composition and microstructure of the nickel plate and nickel insert are quite different. It was also found that borides form at the weld between the nickel plate and the special copper alloy, while aluminum-based oxides form most frequently near the joint between the insert and the special copper alloy.

• Keywords: special copper alloys, nickel, borides, characterization of microstructure, scanning electron microscopy, energy-dispersive X-ray spectroscopy