20.500.12556/RUL-161029 Vpliv mikrostrukturnih značilnosti na korozijske lastnosti aluminijevih zlitin utrjenih s kvazikristali diplomsko delo Influence of microstructural characteristics on the corrosion properties of aluminium alloys hardened with quasicrystals diploma work V diplomski nalogi je obravnavan vpliv mikrostrukturnih značilnosti na korozijske lastnosti aluminijevih zlitin, utrjenih s kvazikristali. Preiskovana je bila kvazikristalna zlitina Al-Mn-Cu-Mg-Si-Ti (z oznako QC). Kot referenca je bila uporabljena zlitina AlSi9Cu3 (s standardno oznako DIN226). Zlitini sta bili uliti v jekleno kokilo z nadzorovano ohlajevalno hitrostjo. Po pripravi vzorcev je bila opravljena karakterizacija mikrostrukture. Pri kvazikristalni zlitini je v mikrostrukturi prevladovala primarna faza s 5-števno simetrijo, ki predstavlja kvazikristalno fazo. Na zlitinah so bile opravljene meritve potenciala odprtega kroga, linearne polarizacije, impedančne spektroskopije in potenciodinamske polarizacije. Po 1 uri je zlitina QC dosegla potencial odprtega kroga -571,3±37,3 mV, zlitina DIN226 pa -544,8±22,6 mV. Pri meritvah linearne polarizacije je bila v zlitini QC gostota korozijskega toka 111,2±7,0 nA/cm2, pri zlitini DIN226 pa 92,9±31,8 nA/cm2. Meritve impedančne spektroskopije so pokazale vrednost impedance zlitine QC 247,8±15,6 kohm/cm2 in vrednost impedance zlitine DIN226 290,2±66 kohm/cm2. Pri meritvah potenciodinamske polarizacije je bila, s pomočjo Taflove ekstrapolacije, izmerjena vrednost gostote korozijskega toka za zlitino QC 145,1±18,0 nA/cm2 in za zlitino DIN226 145,8±28,2 nA/cm2. Zaradi neponovljivosti rezultatov so bile izračunane standardne deviacije. Z upoštevanjem le-teh je prišlo do sklepa, da ima kvazikristalna zlitina primerljivo dobre korozijske lastnosti kot komercialno zelo uspešna zlitina - AlSi9Cu3. Pri zlitini QC je korozija napadla predvsem fazo ?Al, v okolici delcev intermetalne spojine Al2Cu, in ne kvazikristalne faze, kar kaže na dobro korozijsko odpornost kvazikristalne faze. Za obe zlitini je bilo sicer značilno interkristalno napredovanje korozije. The influence of microstructural features on the corrosion properties of aluminium alloys hardened with quasicrystals is discussed in this Diploma work. The quasicrystalline alloy Al-Mn-Cu-Mg-Si-Ti (designated QC) was investigated. AlSi9Cu3 (DIN226 standard designation) was used as a reference. The two alloys were cast in a steel die with controlled cooling rate. After the preparation of the samples, the microstructure characterisation was carried out. In the quasicrystalline alloy, the microstructure was dominated by a primary phase with 5-fold symmetry, representing the quasicrystalline phase. Open-circuit potential, linear polarisation, impedance spectroscopy and potentiodynamic polarisation measurements were performed on the alloys. After 1 h, the QC alloy reached an open-circuit potential of -571,3±37,3 mV and the DIN226 alloy -544,8±22,6 mV. In the linear polarisation measurements, the corrosion current density was 111.2±7.0 nA/cm2 for alloy QC and 92.9±31.8 nA/cm2 for alloy DIN226. Impedance spectroscopy measurements showed an impedance value of 247,8±15,6 kohm/cm2 for alloy QC and 290,2±66 kohm/cm2 for alloy DIN226. The potentiodynamic polarisation measurements, using Tafel extrapolation, gave a corrosion current density value for the QC alloy of 145,1±18,0 nA/cm2 and for the DIN226 alloy of 145,8±28,2 nA/cm2. Due to the non-repeatability of the results, standard deviations were calculated. Taking these into account, it was concluded that the quasicrystalline alloy has comparably good corrosion properties to the commercially very successful AlSi9Cu3 alloy. In the case of the QC alloy, corrosion attacked mainly the αAl phase, in the vicinity of the Al2Cu intermetallic compound particles and not the quasicrystalline phase, indicating good corrosion resistance of the quasicrystalline phase. Both alloys were characterised by intergranular corrosion progression. kvazikristali korozija aluminijeve zlitine mikrostruktura elektrokemijske meritve quasicrystals corrosion aluminium alloys microstructure electrochemical measurements true false false T. Drevenšek Slovenski jezik Angleški jezik Diplomsko delo/naloga 2024-09-06 09:02:03 2024-09-06 09:02:06 2024-10-18 10:28:00 0000-00-00 00:00:00 2024 0 Ljubljana 0 Ljubljana XII, 42 f. 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 669 100823 212067587 22389.pdf 22389.pdf 1 FDCFBD63FC5B8FF2737E642B7B5510FA 8c4c74ad8dd71f1a61d36aac1db84546613b7464e958a4c4052798b74561ddf6 e8dc12e2-6c1d-11ef-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=189877 Naravoslovnotehniška fakulteta 0 0 0