1. Fatigue and fracture characterisation of copper-brazed 316L stainless steelTonica Bončina, Franc Zupanič, Branko Nečemer, Roman Satošek, Erik Rihter, Srečko Glodež, 2026, original scientific article Abstract: This study focuses on the mechanical, fatigue and metallographic characterisation of copper-brazed 316L stainless steel for the potential use in different plate heat exchangers (PHE) applications. The quasi-static and fatigue tests have been performed on the specially designed copper-brazed tensile specimens to obtain the engineering stress–strain diagram and the fatigue life curve of the analysed brazed joint. Furthermore, a comprehensive metallographic investigation has been done, focusing on (i) material characterisation of asreceived stainless steel 316L, (ii) characterisation of the brazed joint and (iii) fractographic analyses of fractured surfaces by quasi-static and fatigue loading. The obtained experimental results may be beneficial for designing copper-brazed plate heat exchangers in the future.
Keywords: brazed joint, fatigue, experimental testing, metallographic investigation
Published in DKUM: 28.11.2025; Views: 0; Downloads: 2
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2. Metallography of quasicrystals in AL-alloysTonica Bončina, Franc Zupanič, 2025, review article Abstract: Quasicrystals are ordered phases without periodicity. They are often found in aluminium and other alloys. They can appear in different sizes. Therefore, several metallographic and characterisation techniques are required to fully determine their shape, size, crystallography, and chemical composition. This review paper gives special attention to identifying quasicrystals in aluminium alloys using classical metallographic techniques, such as etching, deep etching, and particle extraction, which allow the investigation of larger areas by light and scanning electron microscope, giving additional information by combining with complementary high-resolution techniques.
Keywords: metallography, quasicrystals, aluminium, microstructure, microscopy
Published in DKUM: 27.11.2025; Views: 0; Downloads: 2
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3. Mikrostruktura in lastnosti zlitin na osnovi Al-Mn-Cu, obdelanih s trenjem in mešanjem : doktorska disertacijaMatjaž Macerl, 2025, doctoral dissertation Abstract: V doktorskem delu so bile raziskane mikrostrukture in lastnosti dveh zlitin iz sistema Al-Mn-Cu, obdelanih s trenjem in mešanjem (FSP) in varjenih s trenjem in mešanjem ( FSW), ki imata v mikrostrukturi ali kvazikristalne faze, ki so nastale pri strjevanju, ali mešanico kvazikristalnih in L12-Al3X izločkov, ki nastanejo pri umetnem staranju.
Z visokohitrostnnim dvovaljnim litjem zlitine Al94Mn2Cu2Be smo uspešno izdelali lite trakove, pri katerem v mikrostrukturi nastane v meddendritnem prostoru kvazikristalni evtektik. Primarni delci kvazikristalnega aproksimanta Al15Mn3Be2 so nakopičeni predvsem v sredini traku in s tem zmanjšajo žilavost zlitine. Mikrostrukturo zlitine sestavlja -Al, ikozaedrični kvazikristal IQC, θ-Al2Cu, Be4Al (Mn, Cu) in Al15Mn3Be2.
Obdelava s trenjem in mešanjem FSP je močno spremenila mikrostrukturo zlitine Al94Mn2Cu2Be2 v območju mešanja. Veliki primarni delci Al15Mn3Be2 in kvazikristalni evtektik so se zdrobili in pretvorili v stabilno fazo 1-Al29Mn6Cu4. Večji vnos energije pri FSP in FSW je privedel do zmanjšanja trdote v območju mešanja, povečala se je natezna trdnost, udarna žilavost, kritične vrednosti lomne žilavosti JIC in KJIC ter odpornost proti napredovanju razpoke.
Zlitina Al-Mn-Cu, mikrolegirana z elementi Be, Sc, Zr, Cr in V, označena z AlMnCu(M), je bila po litju v bakreno kokilo obdelana s FSP. Lite plošče smo varili med seboj in s komercialno zlitino EN AW 6082 s trenjem in mešanjem FSW. Največji delež v zlitini Al-Mn-Cu(M) je zavzemala faza α-Al. V meddendritnih prostorih so bile po litju identificirane faze Al4Mn, θ-Al2Cu, IQC in Al2Cu(Sc). Po toplotni obdelavi so nastali trije tipi izločkov: ikozaedrični kvazikristalni, dekagonalni kvazikristalni in L12-Al3(Sc, Zr). Toplotna obdelava je bistveno povečala trdoto in povzročila, da je bilo območje mešanja po FSP v toplotnoobdelanih vzorcih manjše kot v litih vzorcih. Trdota v območju mešanja se je zmanjševala z večjim vnosom energije. V območju mešanja je bila drobna disperzija faze τ1- Al29Mn6Cu4. Mikrolegirana zlitina Al-Mn-Cu(M) se je uspešno varila z zlitino EN AW 6082 v stanju T6. Območje mešanja je bilo nesimetrično in bolj pomaknjeno v zlitino EN AW 6082. Pri intenzivnejšem mešanju se je povečala trdota v območju mešanja.
Keywords: aluminijeve zlitine, kvazikristali, mikrostruktura, obdelava in varjenje s trenjem in mešanjem, mehanske lastnosti
Published in DKUM: 19.11.2025; Views: 0; Downloads: 14
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4. Strižna trdnost lotnih spojev toplotnih izmenjevalcev : magistrsko deloŽan Dvoršak, 2025, master's thesis Abstract: V magistrski nalogi smo obravnavali strižno trdnost lotnih spojev toplotnih izmenjevalcev, ki so bili izdelani iz nerjavnega jekla in spojeni s postopkom vakuumskega lotanja. V okviru naše raziskave so bili izvedeni statični in dinamični strižni testi, katerih rezultati so nam podali materialne lastnosti spoja in S-N diagram življenjske dobe. V nadaljevanju je bila izvedena metalografska analiza na nepretrganem vzorcu in vzorcu s statično ter dinamično obremenitvijo. Pri tem smo izvedli tudi meritev mikrotrdote na osnovnem materialu in v okolici spoja. Na vzorcih, ki so bili utrujani, pa smo izvedli še fraktografsko analizo v kombinaciji z EDS analizo mikrostrukture. S pomočjo analiz smo uspeli povezati mehanske lastnosti spojev z njihovo mikrostrukturo in opredeliti vpliv difuzije, utrjevanja ter morebitnih napak v spoju z njihovo nosilnostjo in življenjsko dobo.
Keywords: toplotni izmenjevalec, lotni spoj, statični in dinamični strižni testi, metalografska analiza, fraktografska analiza, mikrotrdota
Published in DKUM: 11.11.2025; Views: 0; Downloads: 11
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5. Načrtovanje in izvedba vgradnje steklenih okenc na kovinsko ohišje radarjaJernej Nejc Korenak, 2025, undergraduate thesis Abstract: V diplomskem delu je predstavljeno načrtovanje in izvedba vgradnje steklenega okenca na kovinsko ohišje radarja. Analizirani so bili različni materiali stekel in aluminijeve zlitine AA 5052, njihove mehanske, fizikalne in kemijske lastnosti ter načini spajanja stekla s kovino. Poseben poudarek je namenjen lepilnim spojem, kjer so bile preučene lastnosti epoksidnih, silikonskih in MS-polimernih lepil.
Razvit je bil tehnološki postopek vgradnje, ki vključuje pripravo površin, nanašanje lepila, umeščanje stekla in kontrolirano sušenje. Za preverjanje zanesljivosti spoja so bili izvedeni preizkusi v solni in temperaturni komori ter tlačni preizkusi.
Rezultati raziskave dokazujejo, da je z ustrezno izbiro materialov in postopkov mogoče doseči kakovosten, trden in zanesljiv spoj med steklom in aluminijem.
Keywords: lepljenje stekla, kontrola kakovosti, kakovost spoja
Published in DKUM: 09.10.2025; Views: 0; Downloads: 0 |
6. 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: 11
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7. 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: 7
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8. 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: 26
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9. 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: 31
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10. 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: 44
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