magistrsko delo
Anna Timicheva (Avtor), Jože Medved (Mentor), Maja Vončina (Komentor)

Povzetek

Kompoziti so trdni materiali sestavljeni iz matrice in utrjevalne faze. Zaradi svojih raznolikih in vrhunskih lastnosti se kompoziti z aluminijevo matrico (AMC) veliko uporabljajo v industriji in so še vedno predmet zanimanja številnih raziskovalcev. Med aluminijevimi kompoziti je kompozit ojačan z intermetalno spojino Mg2Si v obliki delcev (Al-Mg2Si) najbolj priljubljen zaradi nizke gostote in hkrati visoke trdote, visoke temperature tališča in nizkega koeficienta temperaturnega raztezka. Intermetalna ojačitvena Mg2Si faza se tvori »in-situ« pri procesu izdelave kompozita, ki je mogoč s preprostimi tehnikami litja. Grobi delci ojačitvene faze nepravilnih oblik v litem stanju, ki nastanejo pri »in-situ« izdelavi, znižajo predvsem natezno trdnost in duktilnost končnega kompozita. Mehanske lastnosti in mikrostrukturne nevšečnosti lahko izboljšamo s homogenizacijskim žarjenjem. Proces homogenizacije je toplotna obdelava, s katerim se odpravijo nizkotaljive evtektike in kristalne izceje, spremeni se oblika intermetalnih faz ter nastanejo enakomerno razporejeni, drobni utrjevalni izločki. Namen magistrskega dela je bil sintetizirati, homogenizirati in okarakterizirati vzorce kompozita Al-Mg2Si po 4, 12, 24, 48 in 96 urah žarjenja v električni uporovni peči pri 430 in 520 °C. Izrisali smo ravnotežni fazni diagram in Scheilove krivulje v programu Thermo-Calc. Izvedli smo tudi enostavno termično analizo (ETA) in izrisali ohlajevalne krivulje v programu Origin ter diferenčno vrstično kalorimetrijo (DSC). Izvedena je bila tudi mikrostrukturna karakterizacija za opredelitev vrste, deleža in morfologije faz v litem stanju in po homogenizaciji. Rezultati DSC in metalografske analize so pokazali, da so v litem in homogeniziranih vzorcih prisotne primarna Mg2Si faza, evtektiki (?Al + Al13Fe4),(?Al + Mg2Si) in (?Al + Mg2Si + ßSi). Samo vzorec v litem stanju vsebuje še evtektik (?Al + ß-Al3Mg2) pri nižji temperaturi, ki po homogenizaciji izgine. Poligonalne delci primarne Mg2Si faze se začnejo zaobljati po 24-ih urah homogenizaciji, po 96-ih urah pa so že opazno bolj zaobljene. Z večanjem časa homogenizacije postane tudi evtektik (?Al + Mg2Si) bolj droben in bolj okrogel.

Ključne besede

»in-situ« kompozit Al-Mg2Si;homogenizacija;DSC;primarna faza;evtektik;

Podatki

Jezik: Slovenski jezik
Leto izida:
Tipologija: 2.09 - Magistrsko delo
Organizacija: UL NTF - Naravoslovnotehniška fakulteta
Založnik: [A. Urh]
UDK: 669
COBISS: 230289667 Povezava se bo odprla v novem oknu
Št. ogledov: 156
Št. prenosov: 34
Ocena: 0 (0 glasov)
Metapodatki: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Ostali podatki

Sekundarni jezik: Angleški jezik
Sekundarni naslov: synthesis and homogenization of aluminium composite reinforced with Mg2Si
Sekundarni povzetek: Composites are solid materials consisting of a matrix and reinforcement. Due to their versatility and superior properties, aluminium matrix composites (AMC) are widely used in industry and are still the subject of interest for many researchers. Among aluminium composites, the composite reinforced with particles of the Mg2Si intermetallic phase (Al-Mg2Si) is the most popular due to its low density and high hardness at the same time, high melting temperature and low thermal expansion coefficient. The intermetallic reinforcing Mg2Si phase is formed "in-situ" in the composite manufacturing process, which is possible with simple casting techniques. Coarse particles of the reinforcement phase of irregular shapes in the as-cast state which are formed during "in-situ" production mainly reduce the tensile strength and ductility of the final composite. The mechanical properties and microstructural disadvantages can be improved by homogenization annealing. The homogenization process is a heat treatment that eliminates low-melting eutectics and crystalline precipitates, changes the shape of the intermetal phases, and creates uniformly distributed, fine hardening precipitates. The purpose of the master's thesis was to synthesize, homogenize and characterize Al-Mg2Si composite samples after 4, 12, 24, 48 and 96 hours of homogenization treatment in an electric resistance furnace at 430 and 520 °C. We plotted the equilibrium phase diagram and Scheil curves in the Thermo-Calc program. We also performed simple thermal analysis (ETA) and plotted cooling curves in the Origin program and differential scanning calorimetry (DSC). Microstructural characterization was also performed to define the type, proportion and morphology of phases in the as-cast and homogenized samples. The results of DSC and metallographic analysis showed that the primary Mg2Si phase, eutectics (αAl + Al13Fe4), (αAl + Mg2Si) and (αAl + Mg2Si + βSi) are present in the as-cast and homogenized samples. Only the sample in the as-cast state still contains the eutectic (αAl + β-Al3Mg2) at a lower temperature which disappears after homogenization. The polygonal particles of the primary Mg2Si phase begin to become rounder after 24 hours of homogenization and after 96 hours they are noticeably rounder. As the homogenization time increases, the eutectic (αAl + Mg2Si) also becomes finer and rounder.
Sekundarne ključne besede: "in-situ" Al-Mg2Si composite;homogenization;DSC;primary phase;eutectic;
Vrsta dela (COBISS): Magistrsko delo/naloga
Študijski program: 0
Konec prepovedi (OpenAIRE): 1970-01-01
Strani: XVI, 52 f.
ID: 25907320