20.500.12556/DKUM-59225 Notranja oksidacija mikrolegiranega zlata za medicinske aplikacije Internal oxidation of microalloying gold for medical application V doktorski disertaciji je obravnavana problematike izdelave mikrolegiranega disperzijsko utrjenega zlata z disperzijo oksidov (La2O3), redko zemeljskega elementa (La) s procesom notranje oksidacije ter študija biokompatibilnosti materiala.. V prvem delu raziskav smo izdelali zlitino Au – 0,5 ut.% La, s postopkom klasičnega litja. Rezultati karakterizacije so pokazali, da že zelo majhna količina mikrolegirnega elementa lantana v zlati zlitini, povzroči tvorbo intermetane faze Au6La, ki pomembno izboljša mehanske lastnosti mikrolegiranega zlata, v primerjavi s čistim zlatom. V drugem delu smo s tehnologijo hitrega strjevanja in valjanja, izdelali trakove z metastabilno mikrostrukturo. S hitrim strjevanjem zlitine Au - 0,5 ut.% La smo dosegli spremembo morfologije strjevanja. Mikrostruktura hitro strjenih trakov sestoji iz zelo finih zrn αAu, s premerom do nekaj mikrometrov ter homogeno razporejeno intermetalno fazo (Au6La), po celotnem preseku traku. Izmerjena trdota trakov je pokazala, da se je v primerjavi z litim stanjem, trdota povečala za skoraj 20 %. Valjane trakove smo rekristalizacijsko žarili in ugotovili, da že majhen dodatek 0,5 % La, zvišuje temperaturo rekristalizacije do 200 K in povzroči rekristalizacijski zastoj. Karakterizacija materiala, je pokazala, da intermetalna faza Au6La v valjanih trakovih tvori neprekinjeno mrežo po mejah zrn, ki dodatno niža hitrost rekristalizacije. Sledila je notranja oksidacija zlitine v litem, valjanem in hitro strjenem stanju. Rezultati notranje oksidacije zlitine v litem ter valjanem stanju so pokazale, da proces notranje oksidacije poteče le po mejah kristalnih zrn z oksidacijo lantana iz intermetalne faze (Au6La). Med tem ko notranja oksidacija hitro strjenih trakov poteče s oksidacijo lantana iz trdne raztopine in tvorbo CNO ter delno po mejah zrn s oksidacijo lantana iz intermetalne faze (Au6La) . Na osnovi rezultatov smo identificirali mehanizem notranje oksidacije in postavili model notranje oksidacije zlitine Au- 0,5 ut.% La, ki rezultira v disperzijskem utrjanju mikrolegirane zlate zlitine v površinskem sloju, kljub temu, da je topnost kisika v kristalni mreži zlata zelo majhna. V zaključni fazi smo potrdili, da je material Au-0,5 ut.% La biokompatibilen, kar daje možnost njegove uporabe v obliki tankih nanosov na medicinske implantate. This Doctoral Dissertation presents the production of micro-alloyed dispersion hardened gold, by internal oxidation, with oxides of the rare earth element La (La2O3), which are dispersed homogeneously across the volume of gold. In the first stage, in order to achieve our objective, we produced an alloy of Au – 0.5 wt.% La with a classical casting procedure. The characterization results have shown that a very small amount of the micro-alloying element La in the Au alloy causes the formation of an intermetallic Au6La phase, which improves the mechanical properties of micro-alloyed gold in comparison with pure gold. In the second stage, using a technology of rapid solidification and rolling, we produced strips with a metastable microstructure. With rapid solidification of the alloy Au – 0.5 wt% La, we achieved a change in the solidification morphology. The microstructure of rapidly solidified ribbons consists of very fine grains with a diameter of up to a few micrometers were formed with a nanosized intermetallic phase, which is dispersed homogeneously throughout the volume of the strips. The measured hardness of the strips is 90 HV, which is 20 % higher when compared with the casted alloy. The rolled strips were recrystallization annealed, where we found that even a small addition of 0.5% La increased the recrystallization temperature by 200 K and caused a halt in recrystallization. Namely, the intermetallic phase Au6La in the rolled strips forms a continuous network across the grain boundaries, which further decreases the rate of recrystallization. The next step was to perform an internal oxidation in the as cast alloy, rapidly solidified and rolled strips. The results of internal oxidation of alloy in as cast and rolled state showed that the international oxidation occurred only at the grain bounders, with oxidation La from the intermetallic phase. On the other hand, during internal oxidation of rapidly solidified ribbons the internal oxidation zone was formed by oxidation of La from solid solution and partially with oxidation of La from intermetallic phase. Based on these results, we have identified the mechanism of internal oxidation and set up a model of internal oxidation for micro-alloyed gold in a metastable state, which results from dispersion hardening of the Au alloy, even though the solubility of oxygen in the crystal lattice of Au is very low. In the final stage we confirmed that the alloy Au-0.5 wt.% La is biocompatible, which gives it the possibility for use in the form of thin coatings on medical implants, improving their surface and tribological properties significantly. notranja oksidacija zlato zlitine zlato-lantan biokompatibilnost zlato-lantan zlitin internal oxidation gold gold lanthanum alloys gold lanthanum alloys biocompatibility true true false [T. Zupančič Hartner] Slovenski jezik Angleški jezik Doktorska disertacija 2016-05-09 23:32:45 2016-07-05 12:31:54 2022-06-20 03:06:00 2019-07-11 11:06:54 2016 0 [Mariborg 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 620.17/.18:669.21.055.094.3(043.3) 19655702 URN:SI:UM:DK:0S8CYQ7C EDOK_Zupancic_Hartner_Tjasa_2016.pdf EDOK_Zupancic_Hartner_Tjasa_2016.pdf 1 E283F5E61CDFE0B2B636F2D698755D8A 18864598cc26a0ee39b4f6944c4724cbf0c95401ee6f501d69c8ecec83d1a99b d4345b4a-7c0c-11eb-bb7a-00155d0001ca https://dk.um.si/Dokument.php?lang=slv&id=95949 Fakulteta za strojništvo 0 0 0