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- 저자 : Atef Hamada (검색결과 3 건)
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Walaa Abdel‑Aziem,Atef Hamada,Takehiko Makino,Mohsen A. Hassan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6
The Micro/meso-forming of commercially pure aluminum, AA1070, processed at room temperature by equal channel angularpressing (ECAP) with a die channel angle of 90° through 4 deformation passes has been conducted. Microstructure features,such as grain size, misorientation angle distributions and the developed texture during the four deformation passes of micro/meso-ECAP have been investigated by Electron backscattering diffraction (EBSD) technique. Then, hardness measurementsover the cross-section of the processed samples were correlated with the EBSD analysis. EBSD scans revealed thatextended shear bands are formed and represent the microstructural feature induced during micro/meso-forming. Whereas,a non-uniform grain structure consisting of intensive low-angle grain boundaries was obtained in the first pass, a uniformultrafine-grained structure of high-angle grain boundaries (in the range of 1–2 μm) was achieved at the fourth pass. Consequently,a significant improvement in the hardness value to 65.3%, with respect to the starting material, was achieved due tothe enhancement of the fine grain structure. The texture analysis exhibited that the high plastic shear strain associated withmicro/meso-scale ECAP was capable to develop a weak texture in the flow plane compared to the starting texture.
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Peter Nyanor,Omayma El‑Kady,Hossam M. Yehia,Atef S. Hamada,Koichi Nakamura,Mohsen A. Hassan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5
Aluminum matrix composites reinforced with reduced graphene oxide (rGO) and hybrid of carbon nanotube (CNT) andrGO are fabricated by solution coating powder metallurgy process. The hardness, wear resistance and coefficient of thermalexpansion (CTE) of the reinforced aluminum composites and the associated microstructural changes with rGO range(0.2–0.6 wt%) and hybrids of 0.2 wt% CNT–rGO at different ratios have been investigated. The intensive microstructuralobservations show that rGO is adsorbed on Al particles and uniformly distributed in the Al matrix composites. The hardnessvalues of the composites increase significantly with rGO reinforcement exhibiting the maximum hardness at 0.4 wt% rGO.Compared with the hybrid composites CNT–rGO/Al counterparts fabricated by the same route and wt. percent of 0.2, thehardness values in the hybrid CNT–rGO increase considerably. Similar to the hardness, the results of wear tests also exhibitcorresponding variation in the values of the wear rates. The improvement in the wear resistance of the hybrid CNT–rGO /Alcomposite is pronounced in this work. Whereas the rGO reinforcements decrease significantly the wear rate of the aluminumbaseby 98%, the wear resistance of the corresponding hybrid CNT–rGO is significantly higher than that of the precedingcomposites. Maximum CTE reduction of 28% was recorded for hybrid CNT–rGO (1:1) reinforced composite.
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Peter Nyanor,Omayma El‑Kady,Hossam M. Yehia,Atef S. Hamada,Mohsen A. Hassan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.4
Aluminium (Al) matrix reinforced with carbon nanotubes (CNT), micron-sized titanium carbide (TiC) particles, and bimodal(nano + micron) hybrid TiC–CNT is fabricated by solution ball milling, followed by cold compaction and vacuum sinteringto improve the mechanical properties and reduce thermal expansion. The hardness, wear resistance, compressive strength andCTE of pure Al, 0.6 wt% CNT/Al, 10 wt% TiC/Al, and hybrid 10–0.6 wt% TiC–CNT/Al composites have been investigated inthis work. Analysis of strengthening mechanisms based on theoretical models, microstructure, and properties of constituentmaterials is performed. Microstructure analysis reveals an excellent distribution of the reinforcement phase and no new phaseformation in sintered composites. The hardness value of bimodal TiC–CNT reinforced Al composite is significantly higherthan monomodal TiC reinforced composite, reaching 2.3 times the hardness value of pure Al. Similarly, the wear resistanceimproved, and CTE reduced with CNT and TiC addition but is even significantly better in the hybrid reinforced composite. Experimental values of CTE show good agreement with the theoretical model. The strength and ductility of materials aremutually exclusive, but the compressive strength of pure Al has been doubled without significant loss in ductility throughthe use of bimodal-sized hybrid TiC–CNT reinforcement in this work.
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