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11.
VPLIV TOPLOTNE OBDELAVE NA LASTNOSTI HITRO STRJENIH TRAKOV NA OSNOVI ZLITIN Al- Mn
Tilen Marušič, 2011, undergraduate thesis

Abstract: Materiali igrajo pomembno vlogo v načinu našega življenja. S postopki različnih izdelav in obdelav, lahko izboljšamo njihove uporabne lastnosti. V diplomski nalogi bomo raziskali vpliv toplotne obdelave na lastnosti hitro strjenih trakov na osnovi zlitin aluminij - mangan. V prvem delu je predstavljena liteatura s področja aluminijevih zlitin in kvazikristalov, ter podan pregled standardov za merjenje trdote. Drugi del opisuje eksperimentalno delo, katerega smo izvedli, da smo lahko prišli do rezultatov. Sem spadajo merjenje mikrotrdote, metalografska priprava vzorcev, svetlobna in vrstična elektronska mikroskopija in XRD analiza. Rezultati so nam podali pomemben vpogled v pomen toplote obdelave aluminijevih zlitin dobljenih s hitrim strjevanjem in njihovo možnstjo uporabe. S stroškovno analizo in izračunom lastne cene trakov smo dobili oceno stroškov, kateri nastanejo pri proizvodnji teh trakov.
Keywords: hitro strjevanje, litje na vrteče kolo, kvazikristali, toplotna obdelava, svetlobna mikroskopija, vrstična elektronska mikroskopija, analiza stroškov, kalkulacije
Published: 12.01.2012; Views: 1885; Downloads: 177
.pdf Full text (14,11 MB)

12.
MOŽNOSTI POVEČANJA TRAJNOSTI UDARNIH PLOŠČ ROTORJA V MLINIH ZA MLETJE PREMOGA Z NAVARJANJEM
Matjaž Macerl, 2012, undergraduate thesis

Abstract: V Termoelektrarni Trbovlje za proizvodnjo električne energije kot energent uporabljamo rjavi premog, ki ga meljemo v ventilatorskih mlinih. Rotor mlina je premera 2600 mm in ima na obodu nameščenih 10 do 12 udarnih plošč. Njihova obraba predstavlja velike stroške tekočega kot tudi remontnega vzdrževanja. V nalogi sem predstavil materiale udarnih plošč, ki so se uporabljali v preteklosti. Uvajajo se novi materiali za udarne plošče z navarom iz varilne žice. Uporabljenih oz. predstavljenih je več različnih materialov varilne žice za navarjanje. V praksi se uporabljajo trije do štirje materiali, ki so se izkazali za uporabne. V nalogi želim prikazati namen uporabe ustreznih navarov na udarnih ploščah mlinov, oziroma koliko se posledično s takim načinom vzdrževanja zmanjšajo stroški menjave rotorjev zaradi podaljšanja trajnosti dobe trajanja.
Keywords: udarna plošča, obrabna odpornost, trdota, udarna žilavost, mikrostruktura, abrazija
Published: 22.05.2012; Views: 1190; Downloads: 128
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13.
MODEL INTELIGENTNEGA SISTEMA ZA PODPORO ODLOČANJU PRI IZBIRI POLIMERNIH MATERIALOV V PROCESU RAZVOJA IZDELKOV
Urška Sancin, 2012, doctoral dissertation

Abstract: Proces razvoja izdelka je kompleksen proces, znotraj katerega mora inženir sprejemati mnogo pomembnih odločitev, ki se ne nanašajo le na konstrukcijo, ampak na vse faze dobe trajanja izdelka. Izbira materiala je v sklopu procesa konstruiranja izrednega pomena, saj izbrani material v začetnih fazah razvoja izdelka znatno vpliva na vse prihodnje aktivnosti v procesu, ter na posledice, ki jih ima izdelek na okolico v njegovi celotni dobi trajanja. Pri svojem delu konstrukterji mnogokrat naletijo na dileme v procesu odločanja, pri čemer so mladi, neizkušeni inženirji na začetku kariere, kot tudi mala in srednje velika podjetja, v zapostavljenem položaju, saj pomanjkanje izkušenj posledično pomeni slabši izdelek ali najem strokovnjaka. Vpliv izdelka na okolje je definiran z različnimi parametri ekološkega spektra, ki jih lahko nadzorujemo v procesu izbire materiala. Eden takih je recikliranje, ki je pereča problematika polimernih materialov, saj je delež reciklirane plastike bistveno manjši od deleža drugih materialov. Kvarni vpliv človeka na okolje in izkoriščanje neobnovljivih virov tako kažeta na pomembnost težnje k trajnostnemu razvoju. Z razvojem modela sistema za podporo odločanju pri izbiri polimernih materialov z upoštevanjem okoljskega vidika smo v sklopu doktorske disertacije skušali doprinesti k znanosti tega področja ter predvsem razviti računalniško podporo pri konstruiranju okolju prijaznih izdelkov iz polimernih materialov v inženirski praksi.
Keywords: proces razvoja izdelka, konstruiranje za okolje, izbira materiala, sistem za podporo odločanju, polimerni material, človeško znanje
Published: 06.07.2012; Views: 1773; Downloads: 217
.pdf Full text (2,14 MB)

14.
Characterization of Cu-Al-Ni melt-spun ribbons using a focussed ion beam (FIB)
Franc Zupanič, Elfride Unterweger, Albert C. Kneissl, Ivan Anžel, Gorazd Lojen, 2007, original scientific article

Abstract: This work investigates the possibilities for applying a focussed ion beam (FIB) for the metallographic preparation and characterization of Cu-Al-Ni melt-spun ribbons. Two alloys were selected for this reason: CuAl13Ni4 and CuAl15Ni4. The microstructure of the first alloy was fully martensitic and the microstructure of the second consisted of two phases: martensite and ▫$\gamma_2$▫. It was discovered that with FIB-etching the microstructures of both alloys can be clearly revealed on polished cross-sections of the melt-spun ribbons, as well as on their wheel-side and air-side surfaces. However, better results were obtained when the etched surface was smoother, and finer details were visible when using smaller ion currents. In addition, a study was made into the influence of platinum deposition on the quality of 3D-cross sections. It was found that Pt-deposition is necessary when the edge of the trench should be straight and sharp, and the surface of the 3D cross-section smooth. However, in this case, the microstructure of the ribbons free surface cannot be seen.
Keywords: focussed ion beam, FIB, metallography, melt-spinning, shape memory alloy, Cu-Al-Ni
Published: 31.05.2012; Views: 898; Downloads: 18
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15.
Composition and morphology of diborides in Al-Ti-B alloys after annealing at 1873 K
Franc Zupanič, 2008, original scientific article

Abstract: In the investigation, Al-Ti-B alloys with different Ti/B ratios were annealed at 1873 K for 10 hours. Under this condition diboride particles were in contact with molten aluminium. During annealing considerable growth of remaining unmelted diboride particles took place. The composition of diboride particles shifted extremely close to the composition of pure TiB2 regardless of the Ti/B ratios in the alloys, indicating that in equilibrium almost pure TiB2 coexisted with a melt. Diboride particles were bound with well-defined crystal facets. Types and relative size of the facets depended on the Ti/B ratio. It is strongly indicated that an excess of Ti (B) in the melt over that needed to form TiB2 stabilizes crystal planes having planar arrangement of Ti (B) atoms.V tej raziskavi smo več zlitin Al-Ti-B, ki so imele različna razmerja Ti/B, žarili 10 ur pri 1873 K. V teh razmerah so bili delci diborida v kontaktu z aluminijevo talino. Med žarjenjem so diboridni delci močno zrasli. Njihova sestava se je v vseh raziskanih zlitinah močno približala sestavi čistega TiB2, kar kaže, da je v termodinamskem ravnotežju s talino praktično čisti TiB2. Diboridni delci so bili obdani s kristalnimi fasetami. Vrsta in relativna velikost faset je bila močno odvisna od razmerja Ti/B. Obstajajo trdni dokazi, da presežek Ti (B) nad vrednostjo, ki je potrebna za tvorbo TiB2, stabilizira kristalne ravnine, ki imajo ravninsko razporeditev Ti (B) atomov.
Keywords: Al-Ti-B alloys, diboride phase, high-temperature annealing, morphology, microstructure
Published: 31.05.2012; Views: 985; Downloads: 15
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16.
Development of an Al-Mn-Be-Cu alloy with improved quasicrystalline forming ability
Franc Zupanič, Tonica Bončina, Niko Rozman, Ivan Anžel, Werner Grogger, Christian Gspan, Ferdinand Hofer, Boštjan Markoli, 2008, original scientific article

Abstract: An Al94Mn2Be2Cu2 cast alloy was developed displaying increased quasicrystalline formation ability at moderate cooling rates. The as-cast microstructure consisted of a mainly icosahedral phase in the Al-matrix. The microstructure remained stable during uniform heating to 580 °C and isothermalannealing at 400 °C. Most of the icosahedral phase was preserved even after 24 h annealing at 500 °C. For that reason, this alloy presents a promising basis for further development of cast Al-alloys containing quasicrystals.
Keywords: alluminium alloys, casting, quasicrystals, TEM, SEM
Published: 31.05.2012; Views: 1206; Downloads: 71
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17.
Metallographic techniques for the characterization of quasicrystalline phases in aluminium alloys
Tonica Bončina, Boštjan Markoli, Ivan Anžel, Franc Zupanič, 2008, original scientific article

Abstract: Several Al-alloys strengthened by quasicrystalline phases have been developed over the last few years showing the considerable potential for practical application. Therefore there is a strong need for developing new metallographic methods or adapting the traditional ones in order to identify and characterize quasicrystalline phases in a reliable, quick and economical way. This paper describes different techniques: the classical metallographic method, deep etching, particle extraction technique and cross-sectioning using focused ion beam (FIB), and discusses their advantages and disadvantages when identifying quasicrystalline particles. It was discovered that particle extraction techniques are very powerful methods for the identification of phases according to their morphology, and preparation of quality samples for X-ray diffraction (XRD). Transmission electron microscopy (TEM) analyses are also possible provided the extracted particles are thin enough.
Keywords: alluminium alloys, quasicrystal, metallography, deep etching, particle extraction
Published: 31.05.2012; Views: 1297; Downloads: 79
URL Link to full text

18.
Characterization of cast Al86Mn3Be11 alloy
Tonica Bončina, Boštjan Markoli, Franc Zupanič, 2009, original scientific article

Abstract: An Al86Mn3Be11 alloy cast into copper mould was subjected to metallographic investigation. The as-cast microstructure consisted of a quasicrystalline icosahedral phase (i-phase), Be4AlMn phase and, occasionally, a hexagonal phase. Al-rich solid solution represented the dominant phase. The chemical compositions of phases were determined using AES. The composition of the Be4AlMn slightly deviated from the stoichiometric composition, whereas the composition of the i-phase was approximately Al52Mn18Be30, containing an appreciable amount of Be. The average composition of the hexagonal phase was Al66Mn21Be13. Deep etching and particle extraction provided a deep insight into the three-dimensional morphology of the i-phase and the hexagonal phase, whereas Be4AlMn was slightly attacked by the etchant. The i-phase was present predominantly in the form of dendrites and a rodlike eutectic phase. The hexagonal phase was primarily in the form of hexagonal platelets, whereas Be4AlMn was rather irregular in shape. The morphology of the i-phase can be explained by predominant growth in 3-fold directions and the lowest energy of the 5-fold planes, leading to the faceting and adopting a pentagonal dodecahedron shape. The brightnesses of phases in the backscattered electron images were rationalized by determining their backscattering coefficients. TEM investigation showed considerable phason strain in the i-phase, and the polycrystalline nature of the Be4AlMn phase.
Keywords: aluminium alloys, deep etching, metallography, particle extraction, quasicrystal
Published: 31.05.2012; Views: 1190; Downloads: 63
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19.
The solidification path of the complex metallic Al-Mn-Be alloy
Boštjan Markoli, Tonica Bončina, Franc Zupanič, 2010, published scientific conference contribution

Abstract: The solidification paths of the Al86.1Mn2.5Be11.4 and Al84Mn5.1Be10.9 alloys, melt spun, cast into a copper mould and controlled cooled (during DSC) were investigated by means of light-optical microscopy (LOM), differential scanning calorimetry (DSC) combined with thermogravimetry (TG) or simultaneous thermal analysis (STA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and the X-ray diffraction (XRD) line in Elletra Trieste, Italy. The constitutions of samplesfrom both alloys were examined in all three states, i.e., after melt spinning, after casting into a copper mould and after differential scanning calorimetry. It was established that in the cast and controlled-cooled specimens the alloys consisted of an aluminium-rich ▫$alpha$▫Al-matrix, and the Al4Mn and Be4AlMn phases. In the case of casting and DSC the primary crystallization began with the precipitation of the Be4AlMn phase, followed by what can most likely be characterized as a uni-variant binary eutectic reaction L > (Be4AlMn + Al4Mn). The solidification process continued with an invariant ternary eutectic reaction, where the remaining melt (L) formed the heterogeneous structure (▫$alpha$▫Al + Al4Mn + Be4AlMn) or a ternary eutectic. When extremely high cooling rates were employed, as is the case with melt-spinning,the constituting phases of both alloys were precipitated in a very small form and the Be4AlMn phase was completely absent in the form of primary polygonal particles and replaced by the icosahedral quasicrystalline phase or the i-phase. There was also no evidence of the Al4Mn phase. The distribution, size and shape of all the constituents in the melt-spun alloys also varied from the contact surface towards the free surface of the ribbons. The smallest constituents were established at the contact surface, measuring less than 0.1 ▫$mu$▫m, to 0.5 ▫$mu$▫m at the free surface. The grains of the aluminium-rich matrix had mean diameters of less than 20 ▫$mu$▫m, close to the freesurface, down to 1 m at the contact surface.
Keywords: complex Al-Mn-Be alloys, metallography, solidification
Published: 31.05.2012; Views: 1240; Downloads: 55
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20.
Imobilizacija letečega pepela z zasteklitvijo
Natalija Orešek, Franc Berk, Niko Samec, Franc Zupanič, 2010, original scientific article

Abstract: Raziskali smo možnost imobilizacije letečega pepela iz sežiga komunalnih odpadkov. Leteči pepel smo skupaj s slovenskim odpadnim steklom stalili in ulili v kovinske kokile, da je nastal pretežno amorfen produkt, tj. steklo, ki smo ga toplotno obdelali, da se je tvorila steklokeramika. Leteči pepel je bil sestavljen iz delcev velikosti <1 m, ki se povezujejo v aglomerate velikosti okrog 180 m. Tali se pri temperaturi okoli 1300 °C in se v tekočem stanju dobro meša z odpadnim steklom. Steklo, nastalo pri litju, se pretvori v steklokeramiko pri žarjenju v temperaturnem območju med 700 °C in 950 °C, pri čemer se tlačna trdnost poveča za dvakrat. Vrednosti izluževanja težkih kovin iz vzorčnega letečega pepela prekoračujejo predpisane mejne vrednosti za odlaganje na odlagališčih za nevarne odpadke, medtem ko so vrednosti za nastalo steklo in steklokeramiko pod predpisanimi vrednostmi. Zasteklen leteči pepel lahko odložimo kot stabiliziran in nereaktiven odpadek na odlagališčih nenevarnih odpadkov, mogoče pa bi ga bilo tudi predelati in uporabiti v koristne namene.
Keywords: leteči pepel, zasteklitev, devitrifikacija, mehanske lastnosti, izluževanje
Published: 31.05.2012; Views: 1145; Downloads: 37
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