1. Microstructure and indentation properties of single-roll and twin-roll casting of a quasicrystal-forming Al-Mn-Cu-Be alloyFranc Zupanič, Matjaž Macerl, Toshio Haga, Tonica Bončina, 2022, original scientific article Abstract: In this investigation, strips of an experimental Al-Mn-Cu-Be alloy were manufactured by
high-speed single-roll and twin-roll casting to stimulate the formation of a quasicrystalline phase
during solidification. The strips were characterised by light microscopy, scanning and transmission
electron microscopy, microchemical analysis, and X-ray diffraction. Indentation testing was used to
determine the mechanical responses of the strips in different areas. A smooth surface was achieved
on both sides of the twin-roll-cast strip, while the free surface of the single-roll-cast strip was rough.
The microstructures in both strips consisted of an Al-rich solid solution matrix embedding several
intermetallic phases Θ-Al2Cu, Be4Al (Mn, Cu), Al15Mn3Be2 and icosahedral quasicrystalline phase
(IQC). The microstructure of the single-roll-cast strip was more uniform than that of the twin-roll-cast
strip. Coarse Al15Mn3Be2 particles appeared in both alloys, especially at the centre of the twinroll strip. These coarse particles adversely affected the strength and ductility. Nevertheless, both
casting methods provided high-cooling rates, enabling the formation of metastable phases, such as
quasicrystals. However, improvements in alloy composition and casting procedure are required to
obtain enhanced microstructures and properties.
Keywords: single-roll casting, twin roll casting, microstructure, quasicrystal, hardness, aluminium, characterisation
Published in DKUM: 24.03.2025; Views: 0; Downloads: 0
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2. Microstructure and surface topography study of nanolayered TiAlN/CrN hard coatingPeter Panjan, Peter Gselman, Matjaž Panjan, Tonica Bončina, Aljaž Drnovšek, Mihaela Albu, Miha Čekada, Franc Zupanič, 2022, original scientific article Abstract: The microstructure and surface topography of PVD hard coatings are among the most
important properties, as they significantly determine their mechanical, tribological and other properties. In this study, we systematically analyzed the microstructure and topography of a TiAlN/CrN
nanolayer coating (NL-TiAlN/CrN), not only because such coatings possess better mechanical and
tribological properties than TiAlN and CrN monolayer coatings, mainly because the contours of the
individual layers, in the cross-sectional STEM or SEM images of such coatings, make it easier to
follow topographic and microstructural changes that occurred during its growth. We investigated
the effects of the substrate rotation modes on the microstructure and surface topography of the
NL-TiAlN/CrN coating, as well as on the periodicity of the nanolayer structure. The influence of the
substrate material and the ion etching methods were also studied, while special attention was given to
the interlayer roughness and influence of non-metallic inclusions in the steel substrates on the growth
of the coating. The topographical features of the NL-TiAlN/CrN coating surface are correlated with
the observations from the cross-sectional TEM and FIB analysis. Selected non-metallic inclusions,
covered by the NL-TiAlN/CrN coating, were prepared for SEM and STEM analyses by the focused
ion beam. The same inclusions were analyzed prior to and after deposition. We found that substrate
rotation modes substantially influence the microstructure, surface topography and periodicity of the
NL-TiAlN/CrN layer. Non-metallic inclusions in the substrates cause the formation of shallow craters
or protrusions, depending on their net removal rates during the substrate pretreatment (polishing
and ion etching), as compared to the matrix.
Keywords: magnetron sputtering, nanolayer hard coatings, growth defects, surface topography, interlayer roughness, non-metallic inclusion, focused ion beam (FIB), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM)
Published in DKUM: 19.03.2025; Views: 0; Downloads: 1
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3. Mehanska karakterizacija in metalografska analiza lotnih spojev za toplotne izmenjevalce : magistrsko deloErik Rihter, 2024, master's thesis Abstract: V magistrskem delu smo ugotovili lastnosti toplotnih izmenjevalcev iz nerjavnega jekla in bakrene folije s pomočjo mehanskih preizkusov, metalografske in fraktografske analize ter meritvami mikrotrdote. Za rezultate dinamičnih testov smo izračunali koeficient in eksponent trdnosti pri utrujanju. Metalografsko analizo smo naredili na vzorcu osnovnega materiala, nepretrganega spoja in pretrganih preizkušancev mehanskih preizkusov. Na vzorcih dinamičnih preizkušancev smo izvedli tudi fraktografsko analizo. Meritve mikrotrdote HV0,1 smo opravili na nerjavnem jeklu, v okolici spoja in na utrujanih vzorcih. Z mikrostrukturnimi analizami in meritvami mikrotrdote smo ugotovili, da pride do utrjevanja materiala glede na amplitudo obremenjevanja.
Keywords: toplotni izmenjevalec, lotni spoj, eksperimentalne raziskave, metalografska analiza, fraktografska analiza, mikrotrdota
Published in DKUM: 11.02.2025; Views: 0; Downloads: 21
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4. Dispersoids in Al-Mg-Si alloy AA 6086 modified by Sc and YFranc Zupanič, Sandi Žist, Mihaela Albu, Ilse Letofsky-Papst, Jaka Burja, Maja Vončina, Tonica Bončina, 2023, original scientific article Keywords: aluminijeve zlitine, toplotna obdelava, mikrostruktura, disperzoidi, dilatometrija, trdota, aluminium alloy, heat treatment, microstructure, dispersoids, dilatometry, DSC, hardness
Published in DKUM: 05.04.2024; Views: 183; Downloads: 21
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5. Comprehensive analysis of different coating materials on the POM substrateTonica Bončina, Srečko Glodež, Brigita Polanec, Lara Hočuršćak, Franc Zupanič, 2023, original scientific article Abstract: This study presents a comprehensive analysis of different coating materials on the POM substrate. Specifically, it investigated physical vapour deposition (PVD) coatings of aluminium (Al), chromium (Cr), and chromium nitride (CrN) of three various thicknesses. The deposition of Al was accomplished through a three-step process, particularly plasma activation, metallisation of Al by magnetron sputtering, and plasma polymerisation. The deposition of Cr was attained using the magnetron sputtering technique in a single step. For the deposition of CrN, a two-step process was employed. The first step involved the metallisation of Cr using magnetron sputtering, while the second step involved the vapour deposition of CrN, obtained through the reactive metallisation of Cr and nitrogen using magnetron sputtering. The focus of the research was to conduct comprehensive indentation tests to obtain the surface hardness of the analysed multilayer coatings, SEM analyses to examine surface morphology, and thorough adhesion analyses between the POM substrate and the appropriate PVD coating.
Keywords: POM, PVD coating, metal coating, adhesion analyses, indentation tests
Published in DKUM: 15.02.2024; Views: 304; Downloads: 38
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6. Fatigue behaviour of brazed joints for heat exchangersBlaž Hanželič, Jernej Kralj, Tonica Bončina, Branko Nečemer, Janez Kramberger, Roman Satošek, Srečko Glodež, 2024, original scientific article Abstract: The plate heat exchanger (PHE) is a component that provides heat to be transferred from hot water to domestic cold water without mixing them with high efficiency. Over the lifetime of the PHE, cyclic pressures act on the brazing points and the plates, and this may lead to fatigue failure. The fatigue behaviour of the PHE, designed using copper-brazed 316L stainless steel, was investigated in this study. First, the fatigue tests under the load ratio R = 0.1 were performed on the Vibrophore 100 testing machine to obtain the S-N curve of the analysed brazed joint. Based on the obtained experimental results, an appropriate material model of the analysed brazed joint has been created, which was validated with numerical calculation in the framework of a program code Ansys. A validated material model was then used for the subsequent numerical analysis of PHE. In order to carry out a numerical calculation using the finite element method (FEM), a three-dimensional model of the heat exchanger was created based on the previous scanning of PHE-geometry. Thereafter, the geometry was parameterised, which allowed us to perform parametric simulations (monitoring different responses depending on the input geometry). Numerical simulations were carried out in the framework of the Ansys 2023-R1 software, whereby the obtained results were analysed, and the responses were appropriately characterised according to previously determined load cases.
Keywords: brazed joint, fatigue, experimental testing, computational analyses, heat exchanger
Published in DKUM: 31.01.2024; Views: 316; Downloads: 62
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7. Fine martensite and beta-grain variational effects on mechanical properties of Ti–6Al–4V while laser parameters change in laser powder bed fusionSnehashis Pal, Tonica Bončina, Gorazd Lojen, Tomaž Brajlih, Erika Švara Fabjan, Nenad Gubeljak, Matjaž Finšgar, Igor Drstvenšek, 2024, original scientific article Keywords: martensite, Ti-6Al-4V, microstructure, tensile strenght, selective laser melting
Published in DKUM: 26.01.2024; Views: 285; Downloads: 22
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8. Wear Behaviour of Multilayer Al-PVD-Coated Polymer GearsTonica Bončina, Brigita Polanec, Franc Zupanič, Srečko Glodež, 2022, original scientific article Abstract: A comprehensive experimental investigation of the wear behaviour of coated spur polymer gears made of POM is performed in this study. Three different thicknesses of aluminium (Al) coatings were investigated and deposited by the Physical Vapour Deposition (PVD) process. The Al coating was deposited in three steps: By plasma activation, metallisation of the aluminium by the magnetron sputtering process, and plasma polymerisation. The wear of the gears was tested on an in-house developed testing rig for different torques (16, 20, and 24 Nm) and a rotational speed of 1000 rpm. The duration of the experiments was set to 13 h, when the tooth thickness and, consequently, the wear of the tooth flank were recorded. The experimental results showed that the influence of metallisation with aluminium surface coatings on the wear behaviour of the analysed polymer gear is not significantly important. The results also showed that the gears with a thicker aluminium coating showed greater wear than gears with a thinner coating or even without a coating. This is probably due to the fact that the aluminium particles that started to deviate during gear operation represented the abrasive material, which led to the faster wear of the contacting surfaces of the meshing gear flanks.
Keywords: polymer gears, aluminium PVD coating, Physical Vapour Deposition process, multilayer coating, wear
Published in DKUM: 15.11.2022; Views: 580; Downloads: 164
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9. VPLIV NIKLJA NA LASTNOSTI ALUMINIJEVIH BRONOV : diplomsko deloDenis Arnšek, 2019, undergraduate thesis Abstract: V diplomskem delu sem se ukvarjal s študijem vpliva različnega deleža niklja na mikrostrukturo in s tem na mehanske lastnosti aluminijevih bronov. Ugotovil in uporabil sem ustrezne metode metalografske priprave vzorcev iz brona in načine kvalitativne in kvantitativne metalografske analize. Določil sem vrste mikrostrukturnih sestavin in delež β-faze. Izvedli smo natezne preskuse pri sobni in povišani temperaturi, udarne preizkuse in meritve trdote. Ugotovil sem povezavo med deležem niklja in trdoto, ter povezavo z drugimi trdnostnimi lastnostmi (natezno trdnostjo in udarno žilavostjo pri sobni ter pri povišani temperaturi).
Keywords: Aluminijevi broni, metalografska analiza, mehanske lastnosti, delež niklja, delež β-faze
Published in DKUM: 07.05.2019; Views: 1465; Downloads: 104
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10. Effect of cooling rate on the microstructure of an Al94Mn2Be2Cu2 alloyTonica Bončina, Boštjan Markoli, Franc Zupanič, 2012, original scientific article Abstract: In this study the effect of the cooling rate on the microstructure of Al94 Mn2 Be2 Cu2 alloy was investigated. The vacuum induction melted and cast alloy was exposed to different cooling rates. The slowest cooling rate was achieved by the DSC (10 K·min^−1), the moderate cooling rate succeeded by casting in the copper mould (≈1 000 K·s−1) and the rapid solidification was performed by melt spinning (up to 10^6 K·s^−1). The microstructure of the DSC-sample consisted of α-Al matrix, and several intermetallics: τ1-Al29 Mn6 Cu4 , Al4 Mn, θ-Al2 Cu and Be4 Al(Mn,Cu). The microstructures of the alloy at moderate and rapid cooling consisted of the α-Al matrix, i-phase and θ-Al2 Cu. Particles of i-phase and θ-Al2 Cu were much smaller and more uniformly distributed in melt-spun ribbons.
Keywords: Al-alloy, metallography, microstructure, cooling rate, solidification
Published in DKUM: 03.07.2017; Views: 1019; Downloads: 104
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