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Abstract: A complementary characterisation of the Al-alloy EN AW-5454 was carried out, intended for obtaining the laser hybrid welding parameters of subassemblies in the automotive industry. The investigation included a microstructural examination and the determination of the alloy’s properties using several analytical methods (HV5 hardness measurement, tensile test, Charpy impact toughness, fracture mechanics analysis). Samples were prepared in the longitudinal and transverse directions of a cold-rolled sheet of EN AW-5454 with thicknesses of 3.5 mm and 4 mm. The measured hardness on the thinner sheet was 5% higher than on the thicker sheet. The tensile and yield strength were nominal, while the elongations were smaller by 2.2–3.2% for the longitudinal samples and by 2.7–13.7% for the transverse samples. The smaller deviations from the nominal values are for the thinner sheet metal. A precise topographical analysis showed the brittle fractures of the samples. The Charpy impact toughness results on the thicker plate showed a 20% greater work needed to break it in the longitudinal direction than in the transverse direction. With the thinner sheet metal, 40% greater work was needed. SEM (scanning electron microscope) analysis has shown that the intermetallic Al6(Mn,Fe) particles in the longitudinal samples were mostly intact, with evidence of tough areas on the upper part of the fracture, indicating a better toughness than the specimens in the transverse direction. More crushed intermetallic particles were observed at the fractures of the transverse samples, and their distribution appeared to be more oriented in the direction of rolling. Fracture mechanics SENB (single edge notch bending) tests and their analysis showed that the resistance of the material to crack propagation in the longitudinal sample was about 50% greater than that in the transverse sample. SEM analysis of the fractures showed that the state of the intermetallic particles in the fracture mechanics testing and the fracture mechanism differed from the one in the Charpy fractures.
Keywords: Al-alloy EN AW-5454, characterisation, microstructure, properties
Published in DKUM: 02.12.2024; Views: 0; Downloads: 0
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Abstract: It is well known that Selective Laser Melting (SLM) does not provide the same mechanical properties in all directions of the part. This is due to the microstructural grain orientation and pore shape in SLM products. Therefore, depending on the direction of the pressure applied to the SLM product, a different manufacturing orientation is required to achieve the best mechanical properties. Changing the microstructural grain orientation is difficult through SLM, but a process to reduce the size and number of the pores can be discovered through different combinations of manufacturing parameters. In prosthodontics, pressure is usually applied in the vertical direction, which leads to compression and bending of crowns with bridges. The compressive load can be easily absorbed in the crowns, but the bending force has a significant effect here. Therefore, a product with high tensile strength and high ductility is needed to survive longer. Considering these requirements, this study determined the best parameters for laser processing by SLM method to reduce porosity and improve mechanical strength and ductility of Co-CrW-Si alloy products. The result is a relative product density of 100% for cubic specimens and a yield strength, ultimate tensile strength, and elongation at break of the tensile specimens of 900 MPa, 1200 MPa, and 15%, respectively, obtained in specimen build-up in the Z direction with a laser power of 60 W and a scanning speed of 450 mm/s. Eventually, the best orientation for the production of dental prosthetic elements using the SLM process was determined.
Keywords: cobalt-chromium alloy, dental implant, density, tensile strength, ductility, selective laser melting
Published in DKUM: 03.07.2024; Views: 78; Downloads: 8
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Abstract: The impact of the microstructural properties of a Ti6Al4V alloy on its electrochemical properties, as well as the effect of the α- and β-phases present within it, is still unclear. With the introduction of new, emerging technologies, such as selective laser melting and post heat treatments, the effect of the microstructure on an alloy's corrosion properties has become increasingly interesting from a scientific perspective. When these alloys are produced through different methods, despite an identical chemical composition they have diverse microstructures, and consequently display varying resistance to corrosion. In the present research study, Ti–6Al–4V alloy specimens produced by three different processes, leading to the formation of three different microstructures were investigated: heat treated specimen fabricated by selective laser melting, wrought and cast specimens. The impact of the microstructure of these alloys when immersed in artificial saliva was studied through the use of various electrochemical techniques, by microscopical examinations, and time-of-flight secondary ion mass spectrometry. Corrosion properties were investigated by the measurement of open circuit potential, linear polarization, and potentiodynamic curve measurements followed by microscopical examinations, and time-of-flight secondary ion mass spectrometry examination was conducted to reveal spatial distribution of alloying species on oxide film. It was found that the difference between specimens containing an α+β microstructure was small and not dependent on the aspect ratio of the β-phase, alloy grain size, and vanadium partitioning coefficient, but rather on the size, shape, and content of this phase.
Keywords: Ti6Al4V, dental alloy, microstructure, corrosion resistance, heat treatment, ToF-SIMS
Published in DKUM: 07.05.2024; Views: 198; Downloads: 13
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Keywords: anodizing, corrosion resistance, oxide nanotubes, Ti–13Zr–13Nb alloy, zeta potential
Published in DKUM: 04.04.2024; Views: 193; Downloads: 7
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Keywords: lightweight design, multi-material car body, aluminum alloy, wood veneer, aluminum-wood joints, hybrid joining, static strength, fatigue performance
Published in DKUM: 28.03.2024; Views: 223; Downloads: 13
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