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Browsing Journal Articles by Author "Abdelwahed, M"

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    Microstructural, mechanical, and thermal characterization of constitutive layers in copper-steel functionally graded material manufactured via laser directed energy deposition
    (2025-08) Romano, T; Abdelwahed, M; Bertolo, V; Cecotti, T; Skhosane, Besabakhe S; Mahadevan, G; Popovich, V; Hermans, M; Taha MA; Pityana, Sisa S; Maurizio Vedani
    Copper-steel functionally graded materials combine the thermal conductivity of copper with the mechanical strength of steel. This study examines the microstructural, mechanical, and thermophysical properties of the constitutive layers of copper-4130 steel functionally graded material fabricated via laser directed energy deposition, considering four intermediate compositions: 100% 4130, 75% 4130 – 25% Cu, 50% 4130 – 50% Cu, and 25% 4130 – 75% Cu. It was observed that the amount of Cu-rich terminal liquid governs crack formation and backfilling during solidification, while Cu-Fe liquid phase separation and Marangoni convection within the melt pool generate macrostructures composed of alternating Cu- and Fe-rich phases. Increasing Cu content progressively enhances thermal diffusivity due to the formation of interconnected copper regions. The application of quenching and tempering treatments induced softening of Cu-containing samples due to Cu recrystallization and diffusion from supersaturated Fe-rich phases. Although solidification cracking was only observed in 75% 4130–25% individual samples, the analysis of a complete multilayer structure revealed that interlayer mixing causes local compositional variations, extending cracking susceptibility beyond this region. These findings provide insights into the key factors governing laser directed energy deposition of copper-steel functionally graded materials, supporting process optimization and predictive model development to enhance manufacturability.
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    Microstructural, mechanical, and thermal characterization of constitutive layers in copper-steel functionally graded material manufactured via laser directed energy deposition
    (2025-08) Romano, T; Abdelwahed, M; Bertolo, V; Cecotti, T; Skhosane, Besabakhe S; Mahadevan, G; Popovich, V; Hermans, M; Taha MA; Pityana, Sisa S; Maurizio Vedani
    Copper-steel functionally graded materials combine the thermal conductivity of copper with the mechanical strength of steel. This study examines the microstructural, mechanical, and thermophysical properties of the constitutive layers of copper-4130 steel functionally graded material fabricated via laser directed energy deposition, considering four intermediate compositions: 100% 4130, 75% 4130 – 25% Cu, 50% 4130 – 50% Cu, and 25% 4130 – 75% Cu. It was observed that the amount of Cu-rich terminal liquid governs crack formation and backfilling during solidification, while Cu-Fe liquid phase separation and Marangoni convection within the melt pool generate macrostructures composed of alternating Cu- and Fe-rich phases. Increasing Cu content progressively enhances thermal diffusivity due to the formation of interconnected copper regions. The application of quenching and tempering treatments induced softening of Cu-containing samples due to Cu recrystallization and diffusion from supersaturated Fe-rich phases. Although solidification cracking was only observed in 75% 4130–25% individual samples, the analysis of a complete multilayer structure revealed that interlayer mixing causes local compositional variations, extending cracking susceptibility beyond this region. These findings provide insights into the key factors governing laser directed energy deposition of copper-steel functionally graded materials, supporting process optimization and predictive model development to enhance manufacturability.
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    Microstructure evolution and properties development of in situ processed Ni–Ti alloys by laser directed energy deposition
    (2025-09) Abdelwahed, M; Skhosane, Besabakhe S; Ishola, M; Casati, R; Vedani, M; Pityana, Sisa L; Taha, MA
    This investigation proposes a flexible technique for in situ fabrication of Ni–Ti structures using laser directed energy deposition, in which nickel and titanium powders are separately fed and melted together during laser processing. The proposed mechanism enables controlled flows of powders facilitating a fine-tuning of the desired chemical composition, when compared to the conventional use of pre-mixed feedstocks, in an endeavor toward the laser processing of pseudoelastic Ni–Ti alloys. The results highlighted the possibility of fabricating a wide range of tailored Ni–Ti compositions and microstructures, depending on the powder flow ratios. The developed alloys were classified as either Ni-rich or Ti–rich compositions, in which the Ni-rich alloys were composed of different fractions of B2-NiTi austenite, NiTi/Ni3Ti eutectics, and Ni3Ti intermetallic with a minor presence of NiTi2/Ni2Ti4Ox. While the Ti–rich compositions were mainly dominated by NiTi austenite with a fraction of NiTi2/Ni2Ti4Ox dendrites. Under identical laser processing parameters, the findings showed that the in situ alloyed Ni47.6Ti52.4 composition exhibited a comparable microstructure and pseudoelastic behavior similar to that obtained from a laser processed pre-alloyed powder. The output of the investigation highlights the potential use of the in situ alloying mechanism as a cost-effective and flexible approach for fabricating Ni–Ti alloys with desired compositions and properties.
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    On Microstructure Evolution and Mechanical Behavior of Near Equiatomic Nickel Titanium (NiTi) Alloys Fabricated by Laser Deposition of Elemental Powders
    (2025-07) Zain, EM; Abdelwahed, M; Youssef, AF; Elsabbagh, AM; Pityana, Sisa L; Taha, MA
    Elementary powder of nickel (Ni) and titanium (Ti) were deposited on the surface of a Ti-6Al-4V alloy substrate by direct laser deposition. By varying laser parameters such as power and scan speed, we investigated how these factors affect phase formation, hardness, elastic modulus, and elastic recovery. Microstructural analysis revealed dendritic structure in most specimens, with variations in the formation of second phase precipitates, such as TiNi2 and TiNi3, depending on the processing conditions. Specimens processed with higher laser energy had fewer dendritic structures. A nanoindentation test was carried out to assess the hardness and elastic recovery of the specimens, showing differences in mechanical properties linked to the processing parameters, and it revealed that specimens processed with higher laser energy exhibited superior mechanical properties, with a recovery index reaching 30% in some cases that includes laser power of 1.25 Kw and scan speed of 1.5 m/min. When the optimized laser parameters were used, more homogeneous phases were formed, enhancing both hardness and elasticity. This study shows that direct laser deposition can be adjusted to improve the performance of NiTi alloys for applications that need high strength and elasticity.