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Influence of Heat Treatments on Microstructure of Electron Beam Additive Manufactured Ti-6Al-4V Alloy : magistrsko delo
Damir Skuhala, 2020, master's thesis

Abstract: Additive manufacturing of metallic parts is increasing in popularity and starting to emerge as a new competitive manufacturing process. Printed structures from Ti-6Al-4V titanium alloy, produced by electron beam additive manufacturing (EBAM), possess columnar prior β grains and layer bands, alongside an ultrafine lamellar microstructure, which is prone to low ductility and thus requiring thermal post-processing. Several heat treatments were performed in α + β and β field, in one or multiple stages. The results showed that bi-lamellar microstructure can be obtained, and that selection of annealing temperature and cooling rate determines the morphology, thickness, and distribution of both primary and secondary α features. Mechanical properties were evaluated on three selected heat treatments. Annealing of the As-built condition was performed at 710°C (HT1) and 870°C (HT2), resulting in lamellar microstructure with basketweave morphology. In two-stage heat treatment (HT3), the temperature in the first stage has exceeded β transus, while in the second, annealing was performed again at 870°C. The microstructure was characterized as a mixture of lamellar and bi-lamellar with large α colonies inside the rearranged prior β grains. Air cooling was performed in all HT from the final annealing stage. Strength and hardness have decreased with increasingly coarser microstructural features, while fracture toughness was improved, except in HT1, where the decrease in the fracture toughness was mainly attributed to reduced intrinsic toughening. As-built and HT1 conditions were effected by microstructural texture, causing inconsistent fracture morphology, reduced crack roughness and scattering in results. The influence of texture was decreased by coarser microstructure in HT2, while crack tortuosity was increased. Very unpredictable fracture behaviour was observed in HT3 due to large α colonies, as their orientation determines the areas of ductile or cleavage crack propagation.
Keywords: Titanium alloys, Ti-6Al-4V, additive manufacturing, EBAM, heat treatments, microstructural optimization, mechanical properties, fracture toughness
Published in DKUM: 11.05.2020; Views: 739; Downloads: 150
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1st International FibreNet Science for the Public Day : Book of Abstracts
2019, proceedings

Abstract: First international conference in the scope of FibreNet project funded by European Commission. The conference brings the FibreNet together international representatives from industry and academia to discuss opportunities and strengths related to bio-based fibre products. In three consecutive sessions, fifteen international PhD students will present their research results, guide you along the value-chain of fibre-based products and give you the opportunity to discuss the future of bio-based materials.
Keywords: biobased materials, mechanical properties, paper, packaging, dissemination of research result
Published in DKUM: 08.01.2020; Views: 653; Downloads: 32
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Book of abstracts
2018, other monographs and other completed works

Keywords: mechanical engineering, metalurgy, material properties
Published in DKUM: 22.05.2018; Views: 571; Downloads: 0

An evaluation of marine sediments in terms of their usability in the brick industry : case study Port of Koper
Patrik Baksa, Franka Cepak, Rebeka Kovačič Lukman, Vilma Ducman, 2018, original scientific article

Abstract: A dredging process is essential for the development of harbours and ports, allowing the functional daily operation of the port. The management of dredged material represents a worldwide challenge, especially considering unwanted deposition of material. Because of their chemical, petrographic, mineralogical and homogeneity composition, marine sediments could represent an appropriate raw material for the brick industry, particularly for the production of clay blocks, roofing and ceramic tiles. In this study dredged material from Port of Koper was tested for such use, thus various analyses were carried out in order to determine if the dredged material is environmentally friendly and suitable for use in the brick industry. These included: chemical analysis, mineralogical analysis, particle size analysis, chloride content analysis and tests of firing in a gradient furnace. Furthermore, tests of mechanical properties, as well as tests of the frost-resistance of the samples were carried out. On the basis of the primary analyses and samples prepared in a laboratory, it was confirmed that marine sediments from the Port of Koper, without any additives are only conditionally suitable as a source material for producing brick products, because without additives they exhibit too much shrinkage on drying and firing, as well as high water absorption, this can be improved by the incorporation of suitable additives, for example, virgin clay or other suitable waste material. The approach described herewith can also be followed to assess sediments from other ports and rivers regarding its potential use in clay brick sector.
Keywords: dredge marine sediment, recycling, clay bricks, mechanical properties, chemical analysis
Published in DKUM: 21.12.2017; Views: 1644; Downloads: 131
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Tailoring the mechanical and thermal properties of dicyclopentadiene polyHIPEs with the use of a comonomer
E. H. Mert, Christian Slugovc, Peter Krajnc, 2015, original scientific article

Abstract: The effect of adding a comonomer to dicyclopentadiene in high internal phase emulsions (HIPEs) on the properties of ring-opening metathesis polymerisation (ROMP) derived polyHIPEs has been investigated. With this aim, dicylopentadiene was copolymerised with norbornene in surfactant stabilized high internal phase emulsions. Morphological, mechanical and thermal properties of the resulting materials were investigated with regard to the monomer ratio. The interconnected pore structure was observed for the resulting poly(dicylopentadiene-co-norbornene) polyHIPEs. Furthermore, the new polyHIPE copolymers were found to have an improved thermal stability compared to the poly(dicylopentadiene) homopolymer.
Keywords: mechanical properties, emulsion templating, polyHIPE, dicyclopentadiene, norbornene
Published in DKUM: 07.08.2017; Views: 823; Downloads: 323
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Intelligent system for prediction of mechanical properties of material based on metallographic images
Matej Paulič, David Močnik, Mirko Ficko, Jože Balič, Tomaž Irgolič, Simon Klančnik, 2015, original scientific article

Abstract: This article presents developed intelligent system for prediction of mechanical properties of material based on metallographic images. The system is composed of two modules. The first module of the system is an algorithm for features extraction from metallographic images. The first algorithm reads metallographic image, which was obtained by microscope, followed by image features extraction with developed algorithm and in the end algorithm calculates proportions of the material microstructure. In this research we need to determine proportions of graphite, ferrite and ausferrite from metallographic images as accurately as possible. The second module of the developed system is a system for prediction of mechanical properties of material. Prediction of mechanical properties of material was performed by feed-forward artificial neural network. As inputs into artificial neural network calculated proportions of graphite, ferrite and ausferrite were used, as targets for training mechanical properties of material were used. Training of artificial neural network was performed on quite small database, but with parameters changing we succeeded. Artificial neural network learned to such extent that the error was acceptable. With the oriented neural network we successfully predicted mechanical properties for excluded sample.
Keywords: artificial neural network, factor of phase coherence between the surfaces, fracture toughness, image processing, mechanical properties, metallographic image, ultimate tensile strength, yield strength
Published in DKUM: 12.07.2017; Views: 889; Downloads: 365
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Weldability of microalloyed high strength steels TStE 420 and S960QL
Marko Dunđer, Tomaž Vuherer, Ivan Samardžić, 2014, original scientific article

Abstract: The paper presents research of weldability of microalloyed high strength steels TStE 420 and S960QL after weld thermal cycle simulation. Beside mechanical properties hardness and impact strength, the microstructures of characteristic weld thermal cycled structures for both steels are given. The results will contribure to determination of weakest points in Heat Affected Zone of both steels.
Keywords: weldabilty, high strength steels, mechanical properties, TStE 420, S960QL
Published in DKUM: 03.07.2017; Views: 1770; Downloads: 101
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Mechanical properties of the materials for bruxoguards
Vojkan Lazić, Aleksandra Špadijer Gostović, Nebojša Romčević, Igor Đorđević, Ana Todorović, Rebeka Rudolf, 2014, original scientific article

Abstract: The aim of this study is to investigate the mechanical properties of polymethyl methacrylate (PMMA) and thermoplastic polycarbonate (TPC) materials in order to produce night bruxoguards. For this purpose we used a static tensile test. In the next step the microstructures of PMMA and TPC were observed. Within this framework special attention was paid to the examination of the tensile-test tube fracture surfaces for both materials. This approach revealed that PMMA is a brittle and TPC is a plastic material. Certain mechanical properties and a review of the crucial areas confirmed that the TPC material is extremely favourable for making occlusal splints.
Keywords: polymers, mechanical properties, characterization, bruxoguards, polymethyl methacrylate, thermoplastic polycarbonate
Published in DKUM: 16.03.2017; Views: 1184; Downloads: 94
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Influence of the working technology on the development of alloys H13-w(Cu) 87.5 %
Uroš Artiček, Marko Bojinović, Mihael Brunčko, Ivan Anžel, 2014, original scientific article

Abstract: Most dies in the casting industry for injection moulding are machined from the premium-grade H13 tool steel. They provide excellent performance in terms of mechanical properties and service life; however, these dies are characterised by a relatively low thermal conductivity. The tool-and-die industry is interested in depositing a material of a high thermal conductivity onto steel in order to improve the thermal management and productivity. We have explored the possibility of using copper with a new technology. In this study, the microstructure evolution and mechanical properties are discussed using the Laser Engineered Net ShapingTM (LENSTM) technology. For a better understanding of the solidification, the microstructure of a LENS sample was compared with the microstructure of a reference alloy produced with the ingot-casting technology having the same chemical composition of H13-w(Cu) 87.5 %. We carried out light microscopy, scanning electron microscopy, an EDS microchemical analysis, the tensile test and microhardness testing. The results show a successful fabrication of LENS samples; their microstructure is more homogeneous compared to the castings; they show better mechanical properties and represent a good potential for further development and use.
Keywords: casting, laser engineered net shaping technology, microstructure, mechanical properties
Published in DKUM: 16.03.2017; Views: 1056; Downloads: 87
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