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Wear properties of ECAP-processed ultrafine grained Al-Cu alloys
Abd El Aal, M.I.,El Mahallawy, N.,Shehata, F.A.,Abd El Hameed, M.,Yoon, E.Y.,Kim, H.S. Elsevier Sequoia 2010 Materials science & engineering. properties, micro Vol.527 No.16
The wear properties of equal channel angular pressing (ECAP) Al-2, 3 and 5%Cu alloys under dry sliding conditions using different sliding distances and loads were investigated by pin-on-disc dry sliding wear tests. The wear mass loss decreased remarkably as the number of ECAP passes and Cu content increased, being affected more by the sliding distance than by the applied load under the experimental conditions. The wear mechanism was observed to be adhesive and delamination initially, and an abrasive mechanism also appeared as the sliding distance increased. The analysis of the wear surface indicates a transfer of Fe from the rotating disc to the Al-Cu alloy pin with increases in the sliding distance, the applied load, the number of passes and the copper content.
Tensile Properties and Fracture Characteristics of ECAP-Processed Al and Al-Cu Alloys
Mohamed Ibrahim Abd El Aal,Nahed El Mahallawy,Farouk A. Shehata,Mohamed Abd El Hameed,윤은유,이정환,김형섭 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.5
In the present paper, billets of pure Al, and cast-homogenized Al-2 wt.%, 3 wt.%, and 5 wt.% Cu alloys were successfully processed by equal channel angular pressing (ECAP) up to 10 passes without fracture at room temperature using a die with a channel angle of 110o. Giant strains imposed on workpieces lead to extreme dislocation densities, microstructural refinement, and finally ultrafine grained materials. Tensile tests were employed to examine the fracture modes and fracture surface morphologies of the ECAP-processed Al and Al-Cu alloy samples. In particular, the effects of the number of ECAP passes and the Cu content were investigated.
Recycling of AlSi8Cu3 alloy chips via high pressure torsion
Abd El Aal, M.I.,Yoo Yoon, E.,Seop Kim, H. Elsevier Sequoia 2013 Materials science & engineering. properties, micro Vol.560 No.-
In this paper, AlSi8Cu3 alloy chips were consolidated via HPT at an applied pressure 8GPa for 10 revolutions at room temperature. The microstructure and hardness of the HPT consolidated chips were investigated and compared with those of the HPT processed solid AlSi8Cu3 alloy samples and cold compacted chip samples. The HPT process successfully resulted in fully densified bulk samples with a higher microhardness due to the finer Al matrix grains and Si particles sizes with more grain boundaries with high angles and more homogeneous deformation than those in the HPT processed solid AlSi8Cu3 alloy samples due to the higher imposed total strain.
Abd El Aal, Mohamed Ibrahim,Yong Um, Ho,Yoo Yoon, Eun,Seop Kim, Hyoung Elsevier 2015 Materials science & engineering. properties, micro Vol.625 No.-
<P><B>Abstract</B></P> <P>In this paper, billets of Al-1080 were successfully processed by ECAP up to 1 pass, and a combination of ECAP + extrusion with extrusion ratios of 2 and 8 through a newly designed integrated die at room temperature. The combination of ECAP + extrusion processes was observed to produce finer grain sizes with greater fractions of high angle grain boundaries (HAGBs) than the ECAP. The average grain size was further decreased and the fraction of high angle grain boundaries (HAGBs) was increased with the increase of the extrusion ratio. Direct extrusion after ECAP enhanced the mechanical properties (tensile strength and hardness) with conserving reasonable degree of ductility (elongation %). ECAP and ECAP + extrusion processed samples, showed large dimple size in the tensile fracture surfaces with clear ductile fracture mode.</P>
El Gaby, Mohamed S.A.,Kamal El Dean, Adel M.,Gaber, Abd El Aal M.,Eyada, Hassan A.,Al Kamali, Ahmed S.N. Korean Chemical Society 2003 Bulletin of the Korean Chemical Society Vol.24 No.8
Condensation of 4-cyano-5,6-dimethyl-3-pyridazinone 1 with aromatic aldehydes gave the novel styryl derivatives 2a-c. Refluxing of compound 2a with phosphorus oxychloride furnished 3-chloropyridazine derivative 3. Compound 3 was reacted with thiourea and produced pyridazine-3(2H)thione 4. Thieno[2,3-c]- pyridazines 5a-e were achieved by cycloalkylation of compound 4 with halocompounds in methanol under reflux and in the presence of sodium methoxide. Also, refluxing of compound 4 with N-substituted chloroacetamide in the presence of potassium carbonate afforded thienopyridazines 6a-e. Cyclization of compound 6 with some electrophilic reagents as carbon disulfide and triethyl orthoformate furnished the novel pyrimido[4',5':4,5]thieno[2,3-c]pyridazines 12 and 13a-c, respectively. Diazotisation of compound 6 with sodium nitrite in acetic acid produced the pyridazino[4',3':4,5]thieno[3,2-d][1,2,3]triazines 14a-c. Ternary condensation of compound 1, aromatic aldehydes and malononitrile in ethanol containing piperidine under reflux afforded the novel phthalazines 16a-c. Compound 3 was subjected to some nucleophilic substitution reactions with amines and sodium azide and formed the aminopyridazines 17a, b and tetrazolo[1,5-b]-pyridazine 19, respectively. The structures of the synthesized compounds were established by elemental and spectral analyses.
Mervat M. El-Eshmawy,Hala A. Abd El-Hafez,Walaa Othman El Shabrawy,Ibrahim A. Abdel Aal 대한당뇨병학회 2013 Diabetes and Metabolism Journal Vol.37 No.6
Background: Recent evidence has suggested an association between subclinical hypothyroidism (SCH) and microalbuminuria in patients with type 2 diabetes. However, whether SCH is related to microalbuminuria among subjects with prediabetes has not been studied. Thus, we evaluated the association between SCH and microalbuminuria in a cohort of prediabetic Egyptian adults. Methods: A total of 147 prediabetic subjects and 150 healthy controls matched for age and sex were enrolled in this study. Anthropometric measurements, plasma glucose, lipid profile, homeostasis model assessment of insulin resistance (HOMA-IR),thyroid stimulating hormone (TSH), free thyroxine, triiodothyronine levels, and urinary albumin-creatinine ratio (UACR) were assessed. Results: The prevalence of SCH and microalbuminuria in the prediabetic subjects was higher than that in the healthy controls (16.3% vs. 4%, P<0.001; and 12.9% vs. 5.3%, P=0.02, respectively). Prediabetic subjects with SCH were characterized by significantly higher HOMA-IR, TSH levels, UACR, and prevalence of microalbuminuria than those with euthyroidism. TSH level was associated with total cholesterol (P=0.05), fasting insulin (P=0.01), HOMA-IR (P=0.01), and UACR (P=0.005). UACR was associated with waist circumference (P=0.01), fasting insulin (P=0.05), and HOMA-IR (P=0.02). With multiple logistic regression analysis, SCH was associated with microalbuminuria independent of confounding variables (β=2.59; P=0.01). Conclusion: Our findings suggest that prediabetic subjects with SCH demonstrate higher prevalence of microalbuminuria than their non-SCH counterparts. SCH is also independently associated with microalbuminuria in prediabetic subjects. Screening and treatment for SCH may be warranted in those patients.
3D FEM simulations for the homogeneity of plastic deformation in Al–Cu alloys during ECAP
Mahallawy, Nahed El,Shehata, Farouk A.,Hameed, Mohamed Abd El,Aal, Mohamed Ibrahim Abd El,Kim, Hyoung Seop Elsevier 2010 Materials science & engineering. properties, micro Vol.527 No.6
<P><B>Abstract</B></P><P>Equal channel angular pressing (ECAP) is a material processing method that allows very high strains to be imposed, leading to extreme work hardening and microstructural refinement. To investigate the deformation homogeneity in the transverse direction, rigid-viscoplastic 3D finite element simulations were conducted for the different numbers of ECAP passes of Al with Cu contents 0–5%. The simulation results indicated that the material on the outer side of the die channel undergoes less deformation than that in the inner side due to the formation of a corner gap. It was also found that the homogeneity increased with increasing the number of ECAP passes and the copper content due to the decrease in the size of the corner gap. To verify the 3D finite element simulation results, the microhardness homogeneity across the transverse direction of the billet was measured. The same trend was observed: the homogeneity in hardness increased with increasing the number of ECAP passes and Cu contents from 0% to 5%. The homogeneity of deformation indicated by microhardness and by FEM results was higher for route A compared with route Bc and increases with the number of ECAP passes. The homogeneity in route A was higher than that in route Bc by 10% after 2 passes up to 8 passes.</P>
Ultrasonic relaxation in Zinc–Borate glasses
G.E. El-Falaky,M.S. Gaafar,N.S. Abd El-Aal 한국물리학회 2012 Current Applied Physics Vol.12 No.2
Borate glasses in the system (1 - x) [29Na2O - 4Al2O3 - 67B2O3] - x ZnO with (x ¼ 0, 5, 10, 15, 20, 25, 30,and 35 mol%), have been prepared by the melt quenching technique. The longitudinal ultrasonic attenuation of the prepared sample has been measured using the pulse echo technique at ultrasonic frequencies 2, 4, 6 and 8 MHz in the temperature range between 160 and 300 K. The results showed welldefined peak whose position shifts toward higher temperature with increasing frequency. The mean activation energy is strongly composition sensitive. The position and overall shape of the loss peaks in dependence on composition were analyzed in terms of an assumed loss of standard linear solid type with low dispersion, and a broad distribution of Arrhenius-type relaxation with temperature independent relaxation strength. The dependence of ultrasonic attenuation on temperature has been interpreted in terms of a thermally activated relaxation process which arises when ultrasonic waves disturb the equilibrium of an atom moving in a double-well potential in the glass network. The dependence of activation energy on composition suggests that the structure of these glasses changes at 15 mol% ZnO concentration.
Alaya, M.N.,Youssef, A.M.,Karman, M.,Abd El-Aal, H.E Korean Carbon Society 2006 Carbon Letters Vol.7 No.1
Activated carbons were obtained by activating wild cherry stones with different concentrations of phosphoric acid or zinc chloride at different temperatures. The adsorption of $N_2$ at 77 K and of $CO_2$ at 273 K was followed and the data were analyzes by considering different adsorption models. The activated carbons obtained measured high surface area with the most of the surface in all samples located in micropores. Fair agreement was found between the nitrogen surface areas calculated from the BET-, t-, ${\alpha}$- and DR- methods, although the first three are based on surface coverage whereas the latter is based on micropore filling. The carbon dioxide surface areas calculated by the DA equation were smaller than the comparable nitrogen areas. This was ascribed to domination of surface coverage mechanism, the absence of activated diffusion process. Based on this explanation the $CO_2$-surface areas as calculated by DA equation should be taken with great reservation.