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Keywords: ODS steels, austenitic steels, corrosion, mechanical properties
Published in DiRROS: 02.03.2026; Views: 81; Downloads: 73
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Keywords: bamboo fiber, SEM, magnesium hydroxide, durability, mechanical properties
Published in DiRROS: 02.10.2025; Views: 441; Downloads: 188
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Abstract: This study deals with the mechanical and microstructural characterization of geopolymers synthesized from locally available fly ash. A low calcium fly ash was activated using a sodium silicate solution. Samples were characterized by means of flexural and compressive tests, Fourier Transform Infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), and scanning electron microscopy(SEM). Porosity and pore size distributions were identified using mercury intrusion porosimetry and gas sorption. The compressive strength of the produced geopolymers, which is in the range of 1.6 to 53.3 N/mm2, is strongly related to the water content as well as SiO2/Na2O mass ratio of an alkali activator. The compressive strength significantly increased with decreases in the water content and increased silicon concentration used for the synthesis of geopolymers.
Keywords: geopolymers, fly ash, microstructure, mechanical properties
Published in DiRROS: 05.09.2025; Views: 546; Downloads: 261
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Keywords: ZK61 Mg alloys, extrusion, microstructure, mechanical properties
Published in DiRROS: 22.08.2025; Views: 660; Downloads: 304
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Abstract: 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.
Keywords: PBF-LB/M, beam shaping, IN718, heat treatment, mechanical properties
Published in DiRROS: 07.07.2025; Views: 676; Downloads: 334
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