1. Influence of base plate preheating on laser powder bed fusion–processed EN AW-7075 aluminium aloyNejc Velikajne, Jože Medved, Črtomir Donik, Irena Paulin, 2026, izvirni znanstveni članek Povzetek: The influence of base plate temperature (25, 100, 200, and 400 °C) on the laser powder bed fusion processing of EN AW 7075 was systematically investigated using microstructural characterisation (LM, SEM, EBSD, GROD), chemical analysis, hardness testing, and thermal simulations across a broad range of process parameters. Moderate preheating at 100 °C and 200 °C showed no significant reduction in crack density or changes in grain morphology compared to processing without preheating. At the highest studied temperature—400 °C—a transition to columnar crack networks was observed, accompanied by modified grain orientation, pronounced stress relaxation, and reduced hardness. Independent of preheating temperature, consistent evaporation of Zn (~1 wt.%) and Mg (~0.3 wt.%) occurred during processing. Thermal simulations qualitatively supported the experimental observations, indicating increased thermal retention and displacement with increasing preheating temperature. The results demonstrate that base plate preheating alone is insufficient to suppress hot cracking in EN AW 7075 and may promote alternative crack-growth mechanisms at elevated temperatures, highlighting the need for alternative alloy or process design strategies.
Ključne besede: laser powder bed fusion (LPBF), EN AW 7075, cracks, solidification rate, base plate preheat
Objavljeno v DiRROS: 25.03.2026; Ogledov: 346; Prenosov: 377
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2. Microstructural evolution and its impact on mechanical and corrosion performance of 316L ODS steels processed by mechanical alloying and pulse plasma sinteringAnna Dobkowska, Kalyan Das, Mirosław Jakub Kruszewski, Aleksandra Zielińska, Marlene González, Bogusława Adamczyk-Cieślak, Jiří Kubásek, Jan Pokorný, David Nečas, Črtomir Donik, Irena Paulin, Kamil Majchrowicz, Jarosław Mizera, Matjaž Godec, 2026, izvirni znanstveni članek Ključne besede: ODS steels, austenitic steels, corrosion, mechanical properties
Objavljeno v DiRROS: 02.03.2026; Ogledov: 389; Prenosov: 346
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3. Laser-engineered Inconel 625 for enhanced oxygen evolution electrocatalysisAngelja Kjara Surca, Marjan Bele, Črtomir Donik, Irena Paulin, Martin Šala, Jakob Starec Oman, Miha Osredkar, Mejrema Nuhanović, Jan Ocepek, Matjaž Godec, Goran Dražić, Nejc Hodnik, Luka Suhadolnik, 2026, izvirni znanstveni članek Objavljeno v DiRROS: 02.02.2026; Ogledov: 452; Prenosov: 377
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4. Towards increased strength and retained ductility of Zn-Mg-(Ag) materials for medical devices by adopting powder metallurgy processing routesJiří Kubásek, David Nečas, Vojtěch Hybášek, Eva Jablonská, Črtomir Donik, Irena Paulin, Peter Gogola, Martin Kusý, Jaroslav Fojt, Miroslav Čavojský, Jan Duchoň, Jaroslav Čapek, 2025, izvirni znanstveni članek Povzetek: The development of bioabsorbable zinc-based alloys with tailored mechanical properties and biocompatibility holds great promise for advancing medical implant technology. In this study, Zn-Mg and Zn-Mg-Ag alloys were synthesized using mechanical alloying (MA) followed by extrusion to achieve a combination of enhanced strength, ductility, and corrosion resistance. MA for 4 hours produced ultrafine-grained powders incorporating Mg₂Zn₁₁ intermetallic phases and oxide particles, which contributed to microstructure stabilization during subsequent processing. Extrusion consolidated these powders into dense materials with a uniform grain size of ~700 nm, exhibiting ultimate tensile strengths up to 435 MPa and elongation to fracture of ~12%, representing a significant improvement over conventional processing methods. The addition of silver further enhanced the antibacterial properties, demonstrating notable efficacy against Staphylococcus epidermidis, while maintaining non-cytotoxic behavior in vitro. Corrosion rates remained low, with uniform surface degradation and the formation of protective corrosion layers. This work highlights the efficacy of combining powder metallurgy techniques to bioabsorbable zinc-based alloys with exceptional mechanical performance, corrosion behavior and in vitro cytocompatibility, providing a pathway for next-generation biodegradable medical devices.
Ključne besede: zinc, bioabsorbable materials, mechanical alloying, spark plasma sintering, microstructure
Objavljeno v DiRROS: 05.08.2025; Ogledov: 817; Prenosov: 478
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5. Influence of laser beam shape and post heat-treatment on the microstructure and mechanical properties of nickel-based alloy IN718 manufactured by laser powder bed fusionMatjaž Godec, Narges Mirzabeigi, Črtomir Donik, Danijela Anica Skobir Balantič, Simon Malej, Irena Paulin, Bojan Podgornik, Jonas Grünewald, Tobias Novotny, Florian Bayer, Francisco Ruiz-Zepeda, Katrin Wudy, 2025, izvirni znanstveni članek Povzetek: This study examines the effect of Gaussian and ring-shaped laser beam profiles on the microstructural development and mechanical properties of the PBF-LB/M processed nickel-based alloy Inconel 718 in its as-built and post-heat-treated conditions. Beam shaping was employed to achieve a faster build rate without compromising material properties. One of the objectives was to optimise heat treatment conditions for the beam-shaped profile. The post-heat-treatment process included four different solution annealing temperatures (954 °C, 984 °C, 1034 °C and 1154 °C), followed by two-step ageing, respectively. The microstructure evolution was revealed using scanning electron microscopy (SEM) equipped with energy-dispersive X-ray diffraction (EDS). The mechanical properties in all investigated conditions were evaluated based on tensile tests at room temperature. Using a Gaussian laser beam profile results in a fine-grained microstructure without a strong columnar orientation, while the ring beam profile produces a distinct columnar structure with larger nanodendritic grains and dislocation cells. Both beam profiles exhibit a similar proportion of Laves phase. After post-heat treatment, the Gaussian beam profile generally provides 3-7 % higher mechanical properties. The differences in mechanical properties between horizontal and vertical building directions are greater for ring-shaped laser beam profiles. Heat-treatment temperature above 1034 °C leads to recrystallisation, grain growth and the formation of carbonitrides which reduce mechanical properties. Based on the results, the proposed optimal heat-treatment temperature for both investigated laser beam shapes is 984 °C. At this temperature, tensile strength equalises between horizontal and vertical build directions while yield strength increases, which is beneficial for most applications.
Ključne besede: PBF-LB/M, beam shaping, IN718, heat treatment, mechanical properties
Objavljeno v DiRROS: 07.07.2025; Ogledov: 1061; Prenosov: 538
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6. Tailoring the mechanical properties of PBF-LB/M Inconel 718 through post-processing: hip and heat treatmentsČrtomir Donik, Irena Paulin, Bojan Podgornik, Borut Žužek, Federico Uriati, Katrin Wudy, Matjaž Godec, 2025, izvirni znanstveni članek Ključne besede: PBF-LB/M, IN718, SEM, post-processing-heat treatment, mechanical properties
Objavljeno v DiRROS: 18.06.2025; Ogledov: 1050; Prenosov: 698
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7. Površinska kemija naravnih oksidnih plasti na uporabljenih in novih vzorcih stegneničnih komponent endoproteze kolka iz Ti-6Al-7Nb zlitine : diplomsko deloMatic Petrič, 2023, diplomsko delo Ključne besede: kolčne endoproteze, aseptično omajanje, periprostetična okužba, titanov oksid, polimeri, titanove zlitine, XPS, SEM, EBSD, diplomsko delo
Objavljeno v DiRROS: 18.04.2025; Ogledov: 849; Prenosov: 375
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8. Ultrafine-grained Zn–Mg–Sr alloy synthesized by mechanical alloying and spark plasma sinteringDavid Nečas, Jiří Kubásek, Jan Pinc, Ivo Marek, Črtomir Donik, Irena Paulin, Dalibor Vojtěch, 2022, izvirni znanstveni članek Ključne besede: metals and alloys, biomaterials, mechanical alloying, sintering, nanostructure, compression test
Objavljeno v DiRROS: 01.04.2025; Ogledov: 1156; Prenosov: 635
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9. Recent progress in oxide-dispersion-strengthened (ODS) alloys produced by additive manufacturingPaul J. McGuiness, Irena Paulin, Črtomir Donik, Anna Dobkowska, Jiří Kubásek, Jan Pokorný, Matjaž Godec, 2025, pregledni znanstveni članek Ključne besede: oxide-dispersion-strengthened alloys, additive manufacturing, recent progress and research
Objavljeno v DiRROS: 12.02.2025; Ogledov: 1144; Prenosov: 658
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10. Enhanced performance of austenitic oxide dispersion-strengthened 316L steel: a study on ▫$Y_2O_3$▫ reinforcement and corrosion behaviourJan Pokorný, Jiří Kubásek, Črtomir Donik, David Nečas, Vojtěch Hybášek, Jaroslav Fojt, Anna Dobkowska, Irena Paulin, Jaroslav Čapek, Matjaž Godec, 2025, izvirni znanstveni članek Povzetek: This study explores the mechanical and corrosion properties of yttria-reinforced 316L stainless steel. Powder precursor materials were prepared using mechanical alloying. Varying yttria (Y2O3) contents (1, 3, and 5 wt%) were used to assess its impact on the steel’s properties. X-ray diffraction and scanning electron microscopy confirmed the successful dispersion of Y2O3 within the matrix, with the formation of chromium carbides during spark plasma sintering (SPS). The mechanical properties, including hardness and compressive yield strength, improved with increasing Y2O3 contents, with the highest strength observed in the 316L-5Y2O3 sample. However, corrosion resistance decreased with higher yttria concentrations. The 3 wt% Y2O3 sample exhibited the highest corrosion rate due to localized corrosion in areas enriched with oxide particles and chromium carbides. Electrochemical testing revealed that carbide formation and Cr-depleted regions from SPS processing contributed to the corrosion behaviour. These findings suggest that while yttria reinforcement enhances mechanical strength, optimizing the Y2O3 content and processing methods is crucial to balance both mechanical and corrosion performance in ODS 316L stainless steel.
Ključne besede: mechanical milling, SPS, 316L, austenitic stainless steel, yttria, ODS steel, corrosion, EPR-SL
Objavljeno v DiRROS: 31.01.2025; Ogledov: 1106; Prenosov: 790
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