Utjecaj tehnoloških parametara lijevanja na razvoj mikrostrukturnih i mehaničkih svojstava AlSi7Mg0,3 legure

master's thesis

• Title (english): Influence of the technological casting parameters on the microstructure and mechanical properties development of AlSi7Mg0,3 alloy
• Author: Ivana Gavranović
• Mentor: Zdenka Zovko Brodarac (mentor)
• Mentor: Tomislav Rupčić (pomoć pri izradi, neposredni voditelj)
• Mentor: Vanja Šuica (pomoć pri izradi, neposredni voditelj)
• Committee member: Natalija Dolić (predsjednik povjerenstva)
• Committee member: Zdenka Zovko Brodarac (član povjerenstva)
• Committee member: Ivan Jandrlić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Metallurgy; Sisak
• Defense date and country: 2019-09-24, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Metallurgy

Abstract

Aluminijske legure posjeduju izvrsna mehanička svojstva, fizikalno-kemijska i tehnološka svojstva te su zbog toga pronašle primjenu u automobilskoj, svemirskoj, kemijskoj i prehrambenoj industriji, ali i u elektrotehnici. Primjenu u automobilskoj industriji pronašle su zbog niske gustoće čime se smanjuje masa automobila te se doprinosi smanjenju potrošnje goriva čime se direktno utječe na smanjenje emisije CO2. Jedna od najčešće primjenjivanih legura u autoindustriji je AlSi7Mg0,3 legura. Legura se lijeva u trajne kalupe čime se osiguravaju optimalni uvjeti hlađenja i skrućivanja i postižu bolja mehanička svojstva. S obzirom na geometriju odljevka, lijevanje se provodi tehnologijom gravitacijskog lijevanja sa zakretanjem. U okviru ovog diplomskog rada pokazalo se da različite brzine hlađenja i punjenja kalupa mogu utjecati na razvoj mikrostrukture i mehanička svojstava odljevka. Metalografskim ispitivanjima, osim primarnih αAl dendrita i eutektika (αAl + βSi) uočene su i intermetalne faze na osnovi Fe i Mg. U radu je istražen utjecaj tri različita seta parametara na razvoj mikrostrukture i razvoj αAl u korelaciji s debljinom stijenke: I) optimalni parametri s hlađenjem alata, II) bez hlađenja alata i III) ubrzano punjenje alata. Ispitivanjima je utvrđen pozitivan utjecaj povećanje brzine hlađenja i skrućivanja na usitnjavanje mikrostrukturnih konstituenata, prvenstveno αAl do 25 mm debljine stijenke. Mehaničkim ispitivanjima utvrđene su razlike u vrijednostima vlačne čvrstoće i izduženja za slučajeve I, II i III. U prvom slučaju s optimalnim parametrima lijevanja postižu se najbolji rezultati mehaničkih svojstava. Fraktografskom analizom utvrđeni su uzroci lošijih mehaničkih svojstava u odljevku. Kako bi se utvrdio uzrok nastalih grešaka provedena je numerička simulacija odljevka te je utvrđena poroznosti nastala uslijed stezanja pri skrućivanju i neusmjereno skrućivanje u toplom mjestu.

Abstract (english)

Aluminum alloys have excellent mechanical properties, physical and chemical and technological properties and therefore found application in the automotive, aerospace, chemical and food industry, but also in electrical engineering. They have been used in the automotive industry because of their low density, which reduce the mass of cars and contributes to the reduction of fuel consumption, thereby directly reducing CO2 emissions. One of the most commonly used alloys in the automotive industry is AlSi7Mg0,3 alloy. The alloy has been poured into die which ensures optimal cooling and solidification conditions and better mechanical properties were achieved. Considering casting geometry, casting is poured by gravity tilt casting technology. Within this paper, has been shown that different cooling speed as well as pouring rates can affect development of casting microstructure and mechanical properties. Metallographic examination reveals primary αAl dendrites and eutectics (αAl + βSi) and other intermetallic phases based on Fe and Mg. In this paper the influence of three sets of parameters was investigated on microstructure development and development of αAl in correlation with wall thickness: I) optimal casting parameters with applied cooling casting die, II) casting parameters without cooling and III) casting parameters with faster pouring rate. A positive impact of increased cooling rate and solidification rate on refinement of microstructural constituents first of all at αAl till 25 mm of wall thicknesses. Mechanical testing revealed difference in tensile strength and elongation values for case I, II, and III. In first case with optimal parameters, the best mechanical properties are obtained. Lower mechanical properties caused by defects in casting were determinate by fractography analysis. In order to determine the cause of the defects, a numerical simulation of the casting was carried. Defects occurred in castings were determinated as shrinkage porosity and unidirectional solidification in hot spots.

• Keywords: AlSi7Mg0; 3 legura; parametri lijevanja; mikrostruktura; skrućivanje; poroznost
• Keywords (english): AlSi7Mg0; 3 alloy; casting parameters; wall thickness; microstructure; porosity
• Language: croatian
• URN:NBN: urn:nbn:hr:115:904147
• Study programme: Title: Graduate study program Metallurgy; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka metalurgije (magistar/magistra inženjer/inženjerka metalurgije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-10-10 11:06:25