Alaa Abd El-Rehim - Academia.edu (original) (raw)

Papers by Alaa Abd El-Rehim

Research paper thumbnail of Effect of Strain on the Electronic Structure and Phonon Stability of SrBaSn Half Heusler Alloy

Molecules

This paper presents the strain effects on the structural, electronic and phonon properties of a n... more This paper presents the strain effects on the structural, electronic and phonon properties of a newly proposed SrBaSn half Heusler compound. Since it is stable considering chemical thermodynamics, we tested its strength against uniform strain w.r.t phonon spectrum and it produces a direct bandgap of 0.7 eV. The direct bandgap reduces to 0.19 eV at −12% strain beyond which the structure is unstable. However, an indirect gap of 0.63 eV to 0.39 eV is observed in the range of +5% to +8% strain and afterwards the strain application destabilizes the structure. From elastic parameters, the ductile nature of this material is observed.

Research paper thumbnail of Modelling the Effect of Cu Content on the Microstructure and Vickers Microhardness of Sn-9Zn Binary Eutectic Alloy Using an Artificial Neural Network

Crystals, 2021

The present study aims to clarify the impact of Cu addition and aging conditions on the microstru... more The present study aims to clarify the impact of Cu addition and aging conditions on the microstructure development and mechanical properties of Sn-9Zn binary eutectic alloy. The Sn-9Zn alloys with varying Cu content (0, 1, 2, 3, and 4 wt.%) were fabricated by permanent mold casting. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were utilized to investigate the influence of Cu concentration on the microstructure of pre-aged Sn-9Zn-Cu alloys. The main phases are the primary β-Sn phase, eutectic α-Zn/β-Sn phases, and γ-Cu5Zn8/η-Cu6Sn5/ε-Cu3Sn intermetallic compounds. Vickers microhardness values of Sn-9Zn alloys increased with additions of 1 and 2 wt.% Cu. When the concentration of Cu exceeds 2 wt.%, the values of microhardness declined. Besides, the increase in the aging temperature caused a decrease in the microhardness values for all the investigated alloys. The variations in the microhardness values with Cu content and/or aging temperature were interpret...

Research paper thumbnail of The joint effect of naphthalene-system and defects on dye removal by UiO-66 derivatives

Microporous and Mesoporous Materials, 2021

Research paper thumbnail of Influence of Sb2O3 Nanoparticles Addition on the Thermal, Microstructural and Creep Properties of Hypoeutectic Sn–Bi Solder Alloy

Here we investigate the effects (thermal, microstructural, and creep properties) of adding Sb2O3 ... more Here we investigate the effects (thermal, microstructural, and creep properties) of adding Sb2O3 nanoparticles to a hypoeutectic Sn-5 wt% Bi solder alloy. The Sb2O3-containing solder alloy was prepared by mechanically incorporating 0.5 wt% Sb2O3 nanoparticles into the Sn-5 wt% Bi solder alloy. The addition of nano-sized Sb2O3 particles to the Sn–Bi solder alloy increases the melting temperature, but only slightly. The main phases of the investigated solder alloys include the β-Sn and Bi-rich phases in addition to the crystalline phase of Sb2O3 nanoparticles. No other intermetallic compounds were observed in the β-Sn matrix. The tensile creep experiments have been carried out in the 303–363 K temperature interval under constant stresses ranging from 5.1 to 7.64 MPa. The creep parameters of both solders increased gradually with increasing creep temperature up to 333 K, after which they increased rapidly with relatively higher values. The creep parameters of the Sb2O3-containing solder...

Research paper thumbnail of Nanomaterial-based biosensors for COVID-19 detection

Critical Reviews in Solid State and Materials Sciences, 2021

The COVID-19 pandemic continues to afflict millions of people without respite. The relentless sur... more The COVID-19 pandemic continues to afflict millions of people without respite. The relentless surge in infections is due to insufficient supplies of appropriate vaccines, the long incubation period and high prevalence of SARS-CoV-2, and the lack of widespread detection and diagnosis. The development of low-cost rapid detection and sensing platforms will prove vital in the race to efficiently detect and diagnose COVID-19. Nanomaterial-based biosensors and detectors are particularly promising in this regard, with the potential to play a significant role in inhibiting the spread of COVID-19 by early detection. In this review, various schemes for the detection and diagnosis of COVID-19 are elaborated, with special emphasis on the unique advantages of nanomaterials for these niche applications. Moreover, smart nanomaterials, i.e., nanomaterials that respond to external stimuli by changing their physicochemical properties, are reviewed and evaluated for novel applications related to COVID-19 detection and diagnosis. The prospects of the reviewed materials and systems are discussed in detail, and a roadmap for future research and development is proposed.

Research paper thumbnail of Effect of Bi Content on the Microstructure and Mechanical Performance of Sn-1Ag-0.5Cu Solder Alloy

Crystals, 2021

The purpose of this work is to explore the impact of 0.5, 1.5, 2.5 and 3.5 wt.% Bi additions on t... more The purpose of this work is to explore the impact of 0.5, 1.5, 2.5 and 3.5 wt.% Bi additions on the microstructure and mechanical performance of Sn-1Ag-0.5Cu solder alloy. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were utilized to examine the microstructure of the present solders. Creep measurements have been used for the preliminary assessment of mechanical properties. The steady-state creep rate, έst, diminished as the Bi’s concentration increased and reached 2.5 wt.%, with this trend altering above this point. Furthermore, increasing the aging or testing temperature caused the έst values to increment for all the investigated solders. έst variations with different Bi content and aging temperature were observed by examining the Sn-Ag-Cu solders’ structural evolutions. The mean value of the activation energy of all investigated solder alloys was found to be ∼52 kJ/mol. This value is appropriate to that quoted for the dislocation climb through the core diffusion ...

Research paper thumbnail of Simulation and Prediction of the Vickers Hardness of AZ91 Magnesium Alloy Using Artificial Neural Network Model

Crystals, 2020

In this study, an artificial neural network (ANN) model was used to simulate and predict the Vick... more In this study, an artificial neural network (ANN) model was used to simulate and predict the Vickers hardness of AZ91 magnesium alloy. The samples of AZ91 alloy were aged at different temperatures (Ta = 100 to 300 °C) for different durations (ta = 4 to 192 h) followed by water quenching at 25 °C. The age-hardening response of the samples was investigated by hardness measurements. The microstructure investigations showed that only discontinuous precipitates formed at low aging temperatures (100 and 150 °C), while continuous precipitates invaded all the samples at a high aging temperature (300 °C). Both discontinuous and continuous precipitates formed at the intermediate aging temperatures (200 and 250 °C). X-ray diffraction (XRD) analysis revealed that the microstructure comprised two phases: The α-Mg matrix and intermetallic β-Mg17Al12 phase. The alteration of the crystalline lattice parameters a, c, and c/a ratio with the aging time at various aging temperatures was also investigat...

Research paper thumbnail of Modification of ZIF-8 with triethylamine molecules for enhanced iodine and bromine adsorption

Inorganica Chimica Acta, 2020

Abstract We report a new way to enhance halogen capping properties of ZIF-8 and to protect its st... more Abstract We report a new way to enhance halogen capping properties of ZIF-8 and to protect its structure in a slightly acidic medium. We observed that triethylamine additive in hydrothermal conditions results in modification of the ZIF-8 structure. Triethylamine molecules, which are trapped inside pores, increase the rate of iodine sorption both from hexane and methanol solutions. Moreover, the solution of iodine in methanol has an acidic medium, and it leads to the decomposition of non-modified ZIF-8 sample, while sample obtained in water with triethylamine preserve structure and effectively adsorb iodine. However, bromine molecules were capped by both ZIF-8 samples after 5 min of contact. It makes an eco-friendly scalable hydrothermal synthesis of ZIF-8 more attractive because it combines high crystallinity and porosity of obtained materials with modifications allowed to enhance iodine capping properties and chemical stability.

Research paper thumbnail of MW synthesis of ZIF-65 with a hierarchical porous structure

Microporous and Mesoporous Materials, 2019

Research paper thumbnail of Effect of superimposed oscillations on creep behaviour of Al – 2 4·.5Cu and Al – 2 4·5Cu – 2 0·1In (wt-%) alloys containingθ′ precipitates

Materials Science and Technology, 2007

ABSTRACT The behaviour of both transient and steady state creep of Al24.5Cu and Al24.5Cu20.1In ( ... more ABSTRACT The behaviour of both transient and steady state creep of Al24.5Cu and Al24.5Cu20.1In ( wt-%) alloys was investigated using a constant stress where torsional oscillations of different frequencies and shear strain amplitudes were operated at various working temperatures. An augment in both transient and steady state creep rates was observed by increasing both frequency and shear strain amplitude of the applied oscillations. The mean values of the activation energy of both alloys for both creep stages were found to be equal to that quoted for dislocation intersection mechanism.

Research paper thumbnail of Effect of cyclic stress reduction on high temperature creep characteristics of solid solution Al−2·9 wt-%Mg alloy

Materials Science and Technology, 2011

Research paper thumbnail of Effect of Cyclic Stress Reduction on the Creep Characteristics of AZ91 Magnesium Alloy

Acta Metallurgica Sinica (English Letters), 2015

The creep deformation behavior of aged AZ91 magnesium alloy under the cyclic stress reduction has... more The creep deformation behavior of aged AZ91 magnesium alloy under the cyclic stress reduction has been investigated in the temperature range 353–383 K. The microstructural evolution of the AZ91 magnesium alloy at different heat treatment conditions has been studied using optical microscopy and scanning electron microscopy. The minimum strain rate, \( \dot{\varepsilon}_{\hbox{min} } \), was found to be higher under cyclic stress reduction condition than that under static creep condition for the same maximum stress. Cyclic creep acceleration is interpreted using the interaction of moving dislocations with the existing β-phase (Mg17Al12) precipitates. The mean value of the activation energy of secondary creep stage was found to be equal to that quoted for lattice self-diffusion of magnesium mechanism.

Research paper thumbnail of Plastic deformation of Al-4.5 wt% Cu and Al-4.5 wt% Cu-0.1 wt% In alloys under the effect of cyclic stress reduction

physica status solidi (a), 2004

The plastic deformation behavior of Al − 4.5 wt% Cu and Al − 4.5 wt% Cu − 0.1 wt% In alloys under... more The plastic deformation behavior of Al − 4.5 wt% Cu and Al − 4.5 wt% Cu − 0.1 wt% In alloys under cyclic stress reduction was investigated by studying the creep behavior. The influence of cyclic stress reduction of increasing amplitudes and frequencies was systematically examined at various working temperatures. Both transient and steady-state creep were found to be higher under cyclic stress reduction conditions than under static conditions for the same peak stress. An enhancement of the creep rate was observed above either threshold stress or threshold frequency. A dislocation intersections mechanism was assumed as the rate-controlling mechanism for both creep stages.

Research paper thumbnail of The variation of work-hardening characteristics of Al–1wt% Si and Al–1wt% Si–0.1wt% Zr–0.1wt% Ti alloys

Physica B: Condensed Matter, 2002

Research paper thumbnail of Effect of torsional oscillations on the stress–strain behavior of Al–5wt% Mg alloy

Materials Science and Engineering: A, 2011

The microstructure and mechanical properties of a precipitation hardenable Al–5wt% Mg alloy subje... more The microstructure and mechanical properties of a precipitation hardenable Al–5wt% Mg alloy subjected to low frequency torsional oscillations and aging treatments are reported in the present work. The stress–strain response was examined at different frequencies (1.53–3.3Hz) and at constant shear strain amplitude (φ=5.69×10−4). An excessive in the softening was observed by increasing both frequency of the applied oscillations and deformation

Research paper thumbnail of Transient and steady state creep of age-hardenable Al–5 wt% Mg alloy during superimposed torsional oscillations

Journal of Materials Science, 2012

ABSTRACT An experimental study has been conducted to assess the effect of imposed small torsional... more ABSTRACT An experimental study has been conducted to assess the effect of imposed small torsional oscillations on the creep behavior of Al-5 wt% Mg alloy during phase transformation. A series of tensile tests were conducted on the material with different levels of torsional oscillations and with different aging and matrix temperatures. The carefully designed experiments prove that increasing the shear strain amplitude of torsional oscillations and/or testing temperatures resulted in an increase of both transient and steady state creep parameters. The changes in work-hardening behavior of the samples with aging temperatures were rationalized in view of type, size, and distributions of phases existing in the original matrix. The results clearly show that the mechanism operating in the creep process was the precipitate-dislocation intersection. The microstructure of the samples studied was investigated by transmission electron microscopy.

Research paper thumbnail of The enhancement of creep in Al–22 wt% Ag alloy by cyclic stressing

Journal of Materials Science, 2010

Research paper thumbnail of Effect of grain size on the primary and secondary creep behavior of Sn–3 wt.% Bi alloy

Journal of Materials Science, 2007

Research paper thumbnail of Effect of Cu addition on the microstructure and mechanical properties of AlCoCrFeNiTi0.5 solid-solution alloy

Journal of Alloys and Compounds, 2008

The effect of 0.5, 1, 1.5 and 2 wt% Cu addition on the microstructure and mechanical properties o... more The effect of 0.5, 1, 1.5 and 2 wt% Cu addition on the microstructure and mechanical properties of Al-30 wt% Zn alloy has been investigated by stress-strain tests carried out in the temperature range from 508 to 608 K. The work-hardening parameters of the test alloys decreased with increasing the deformation temperature and exhibited discontinuity at 548 K, resulting two deformation temperature regions, the low-temperature region (below 548 K) and high-temperature region (above 548 K). The activation energy of fracture mechanisms has been calculated and found to be 19.6 and 33.2 kJ/mol at the low and high temperature regions respectively. The operating mechanisms of work-hardening of the test alloys were confirmed by the analysis of X-ray diffraction patterns.

Research paper thumbnail of Effect of structure transformation on the creep characteristics of Sn–3wt% Bi alloy

Journal of Alloys and Compounds, 2007

... Nada [10] studied the effect of Pb-addition and irradiation with gamma rays on the mechanical... more ... Nada [10] studied the effect of Pb-addition and irradiation with gamma rays on the mechanical and thermal properties of Sn–5 wt% Bi alloys prepared by melt spinning technique. ... [8] GS Al-Ganainy, MR Nagy, BA Khalifa and R. Afifi, Phys. Stat. Sol. (a) 158 (1996), p. 463. ...

Research paper thumbnail of Effect of Strain on the Electronic Structure and Phonon Stability of SrBaSn Half Heusler Alloy

Molecules

This paper presents the strain effects on the structural, electronic and phonon properties of a n... more This paper presents the strain effects on the structural, electronic and phonon properties of a newly proposed SrBaSn half Heusler compound. Since it is stable considering chemical thermodynamics, we tested its strength against uniform strain w.r.t phonon spectrum and it produces a direct bandgap of 0.7 eV. The direct bandgap reduces to 0.19 eV at −12% strain beyond which the structure is unstable. However, an indirect gap of 0.63 eV to 0.39 eV is observed in the range of +5% to +8% strain and afterwards the strain application destabilizes the structure. From elastic parameters, the ductile nature of this material is observed.

Research paper thumbnail of Modelling the Effect of Cu Content on the Microstructure and Vickers Microhardness of Sn-9Zn Binary Eutectic Alloy Using an Artificial Neural Network

Crystals, 2021

The present study aims to clarify the impact of Cu addition and aging conditions on the microstru... more The present study aims to clarify the impact of Cu addition and aging conditions on the microstructure development and mechanical properties of Sn-9Zn binary eutectic alloy. The Sn-9Zn alloys with varying Cu content (0, 1, 2, 3, and 4 wt.%) were fabricated by permanent mold casting. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were utilized to investigate the influence of Cu concentration on the microstructure of pre-aged Sn-9Zn-Cu alloys. The main phases are the primary β-Sn phase, eutectic α-Zn/β-Sn phases, and γ-Cu5Zn8/η-Cu6Sn5/ε-Cu3Sn intermetallic compounds. Vickers microhardness values of Sn-9Zn alloys increased with additions of 1 and 2 wt.% Cu. When the concentration of Cu exceeds 2 wt.%, the values of microhardness declined. Besides, the increase in the aging temperature caused a decrease in the microhardness values for all the investigated alloys. The variations in the microhardness values with Cu content and/or aging temperature were interpret...

Research paper thumbnail of The joint effect of naphthalene-system and defects on dye removal by UiO-66 derivatives

Microporous and Mesoporous Materials, 2021

Research paper thumbnail of Influence of Sb2O3 Nanoparticles Addition on the Thermal, Microstructural and Creep Properties of Hypoeutectic Sn–Bi Solder Alloy

Here we investigate the effects (thermal, microstructural, and creep properties) of adding Sb2O3 ... more Here we investigate the effects (thermal, microstructural, and creep properties) of adding Sb2O3 nanoparticles to a hypoeutectic Sn-5 wt% Bi solder alloy. The Sb2O3-containing solder alloy was prepared by mechanically incorporating 0.5 wt% Sb2O3 nanoparticles into the Sn-5 wt% Bi solder alloy. The addition of nano-sized Sb2O3 particles to the Sn–Bi solder alloy increases the melting temperature, but only slightly. The main phases of the investigated solder alloys include the β-Sn and Bi-rich phases in addition to the crystalline phase of Sb2O3 nanoparticles. No other intermetallic compounds were observed in the β-Sn matrix. The tensile creep experiments have been carried out in the 303–363 K temperature interval under constant stresses ranging from 5.1 to 7.64 MPa. The creep parameters of both solders increased gradually with increasing creep temperature up to 333 K, after which they increased rapidly with relatively higher values. The creep parameters of the Sb2O3-containing solder...

Research paper thumbnail of Nanomaterial-based biosensors for COVID-19 detection

Critical Reviews in Solid State and Materials Sciences, 2021

The COVID-19 pandemic continues to afflict millions of people without respite. The relentless sur... more The COVID-19 pandemic continues to afflict millions of people without respite. The relentless surge in infections is due to insufficient supplies of appropriate vaccines, the long incubation period and high prevalence of SARS-CoV-2, and the lack of widespread detection and diagnosis. The development of low-cost rapid detection and sensing platforms will prove vital in the race to efficiently detect and diagnose COVID-19. Nanomaterial-based biosensors and detectors are particularly promising in this regard, with the potential to play a significant role in inhibiting the spread of COVID-19 by early detection. In this review, various schemes for the detection and diagnosis of COVID-19 are elaborated, with special emphasis on the unique advantages of nanomaterials for these niche applications. Moreover, smart nanomaterials, i.e., nanomaterials that respond to external stimuli by changing their physicochemical properties, are reviewed and evaluated for novel applications related to COVID-19 detection and diagnosis. The prospects of the reviewed materials and systems are discussed in detail, and a roadmap for future research and development is proposed.

Research paper thumbnail of Effect of Bi Content on the Microstructure and Mechanical Performance of Sn-1Ag-0.5Cu Solder Alloy

Crystals, 2021

The purpose of this work is to explore the impact of 0.5, 1.5, 2.5 and 3.5 wt.% Bi additions on t... more The purpose of this work is to explore the impact of 0.5, 1.5, 2.5 and 3.5 wt.% Bi additions on the microstructure and mechanical performance of Sn-1Ag-0.5Cu solder alloy. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were utilized to examine the microstructure of the present solders. Creep measurements have been used for the preliminary assessment of mechanical properties. The steady-state creep rate, έst, diminished as the Bi’s concentration increased and reached 2.5 wt.%, with this trend altering above this point. Furthermore, increasing the aging or testing temperature caused the έst values to increment for all the investigated solders. έst variations with different Bi content and aging temperature were observed by examining the Sn-Ag-Cu solders’ structural evolutions. The mean value of the activation energy of all investigated solder alloys was found to be ∼52 kJ/mol. This value is appropriate to that quoted for the dislocation climb through the core diffusion ...

Research paper thumbnail of Simulation and Prediction of the Vickers Hardness of AZ91 Magnesium Alloy Using Artificial Neural Network Model

Crystals, 2020

In this study, an artificial neural network (ANN) model was used to simulate and predict the Vick... more In this study, an artificial neural network (ANN) model was used to simulate and predict the Vickers hardness of AZ91 magnesium alloy. The samples of AZ91 alloy were aged at different temperatures (Ta = 100 to 300 °C) for different durations (ta = 4 to 192 h) followed by water quenching at 25 °C. The age-hardening response of the samples was investigated by hardness measurements. The microstructure investigations showed that only discontinuous precipitates formed at low aging temperatures (100 and 150 °C), while continuous precipitates invaded all the samples at a high aging temperature (300 °C). Both discontinuous and continuous precipitates formed at the intermediate aging temperatures (200 and 250 °C). X-ray diffraction (XRD) analysis revealed that the microstructure comprised two phases: The α-Mg matrix and intermetallic β-Mg17Al12 phase. The alteration of the crystalline lattice parameters a, c, and c/a ratio with the aging time at various aging temperatures was also investigat...

Research paper thumbnail of Modification of ZIF-8 with triethylamine molecules for enhanced iodine and bromine adsorption

Inorganica Chimica Acta, 2020

Abstract We report a new way to enhance halogen capping properties of ZIF-8 and to protect its st... more Abstract We report a new way to enhance halogen capping properties of ZIF-8 and to protect its structure in a slightly acidic medium. We observed that triethylamine additive in hydrothermal conditions results in modification of the ZIF-8 structure. Triethylamine molecules, which are trapped inside pores, increase the rate of iodine sorption both from hexane and methanol solutions. Moreover, the solution of iodine in methanol has an acidic medium, and it leads to the decomposition of non-modified ZIF-8 sample, while sample obtained in water with triethylamine preserve structure and effectively adsorb iodine. However, bromine molecules were capped by both ZIF-8 samples after 5 min of contact. It makes an eco-friendly scalable hydrothermal synthesis of ZIF-8 more attractive because it combines high crystallinity and porosity of obtained materials with modifications allowed to enhance iodine capping properties and chemical stability.

Research paper thumbnail of MW synthesis of ZIF-65 with a hierarchical porous structure

Microporous and Mesoporous Materials, 2019

Research paper thumbnail of Effect of superimposed oscillations on creep behaviour of Al – 2 4·.5Cu and Al – 2 4·5Cu – 2 0·1In (wt-%) alloys containingθ′ precipitates

Materials Science and Technology, 2007

ABSTRACT The behaviour of both transient and steady state creep of Al24.5Cu and Al24.5Cu20.1In ( ... more ABSTRACT The behaviour of both transient and steady state creep of Al24.5Cu and Al24.5Cu20.1In ( wt-%) alloys was investigated using a constant stress where torsional oscillations of different frequencies and shear strain amplitudes were operated at various working temperatures. An augment in both transient and steady state creep rates was observed by increasing both frequency and shear strain amplitude of the applied oscillations. The mean values of the activation energy of both alloys for both creep stages were found to be equal to that quoted for dislocation intersection mechanism.

Research paper thumbnail of Effect of cyclic stress reduction on high temperature creep characteristics of solid solution Al−2·9 wt-%Mg alloy

Materials Science and Technology, 2011

Research paper thumbnail of Effect of Cyclic Stress Reduction on the Creep Characteristics of AZ91 Magnesium Alloy

Acta Metallurgica Sinica (English Letters), 2015

The creep deformation behavior of aged AZ91 magnesium alloy under the cyclic stress reduction has... more The creep deformation behavior of aged AZ91 magnesium alloy under the cyclic stress reduction has been investigated in the temperature range 353–383 K. The microstructural evolution of the AZ91 magnesium alloy at different heat treatment conditions has been studied using optical microscopy and scanning electron microscopy. The minimum strain rate, \( \dot{\varepsilon}_{\hbox{min} } \), was found to be higher under cyclic stress reduction condition than that under static creep condition for the same maximum stress. Cyclic creep acceleration is interpreted using the interaction of moving dislocations with the existing β-phase (Mg17Al12) precipitates. The mean value of the activation energy of secondary creep stage was found to be equal to that quoted for lattice self-diffusion of magnesium mechanism.

Research paper thumbnail of Plastic deformation of Al-4.5 wt% Cu and Al-4.5 wt% Cu-0.1 wt% In alloys under the effect of cyclic stress reduction

physica status solidi (a), 2004

The plastic deformation behavior of Al − 4.5 wt% Cu and Al − 4.5 wt% Cu − 0.1 wt% In alloys under... more The plastic deformation behavior of Al − 4.5 wt% Cu and Al − 4.5 wt% Cu − 0.1 wt% In alloys under cyclic stress reduction was investigated by studying the creep behavior. The influence of cyclic stress reduction of increasing amplitudes and frequencies was systematically examined at various working temperatures. Both transient and steady-state creep were found to be higher under cyclic stress reduction conditions than under static conditions for the same peak stress. An enhancement of the creep rate was observed above either threshold stress or threshold frequency. A dislocation intersections mechanism was assumed as the rate-controlling mechanism for both creep stages.

Research paper thumbnail of The variation of work-hardening characteristics of Al–1wt% Si and Al–1wt% Si–0.1wt% Zr–0.1wt% Ti alloys

Physica B: Condensed Matter, 2002

Research paper thumbnail of Effect of torsional oscillations on the stress–strain behavior of Al–5wt% Mg alloy

Materials Science and Engineering: A, 2011

The microstructure and mechanical properties of a precipitation hardenable Al–5wt% Mg alloy subje... more The microstructure and mechanical properties of a precipitation hardenable Al–5wt% Mg alloy subjected to low frequency torsional oscillations and aging treatments are reported in the present work. The stress–strain response was examined at different frequencies (1.53–3.3Hz) and at constant shear strain amplitude (φ=5.69×10−4). An excessive in the softening was observed by increasing both frequency of the applied oscillations and deformation

Research paper thumbnail of Transient and steady state creep of age-hardenable Al–5 wt% Mg alloy during superimposed torsional oscillations

Journal of Materials Science, 2012

ABSTRACT An experimental study has been conducted to assess the effect of imposed small torsional... more ABSTRACT An experimental study has been conducted to assess the effect of imposed small torsional oscillations on the creep behavior of Al-5 wt% Mg alloy during phase transformation. A series of tensile tests were conducted on the material with different levels of torsional oscillations and with different aging and matrix temperatures. The carefully designed experiments prove that increasing the shear strain amplitude of torsional oscillations and/or testing temperatures resulted in an increase of both transient and steady state creep parameters. The changes in work-hardening behavior of the samples with aging temperatures were rationalized in view of type, size, and distributions of phases existing in the original matrix. The results clearly show that the mechanism operating in the creep process was the precipitate-dislocation intersection. The microstructure of the samples studied was investigated by transmission electron microscopy.

Research paper thumbnail of The enhancement of creep in Al–22 wt% Ag alloy by cyclic stressing

Journal of Materials Science, 2010

Research paper thumbnail of Effect of grain size on the primary and secondary creep behavior of Sn–3 wt.% Bi alloy

Journal of Materials Science, 2007

Research paper thumbnail of Effect of Cu addition on the microstructure and mechanical properties of AlCoCrFeNiTi0.5 solid-solution alloy

Journal of Alloys and Compounds, 2008

The effect of 0.5, 1, 1.5 and 2 wt% Cu addition on the microstructure and mechanical properties o... more The effect of 0.5, 1, 1.5 and 2 wt% Cu addition on the microstructure and mechanical properties of Al-30 wt% Zn alloy has been investigated by stress-strain tests carried out in the temperature range from 508 to 608 K. The work-hardening parameters of the test alloys decreased with increasing the deformation temperature and exhibited discontinuity at 548 K, resulting two deformation temperature regions, the low-temperature region (below 548 K) and high-temperature region (above 548 K). The activation energy of fracture mechanisms has been calculated and found to be 19.6 and 33.2 kJ/mol at the low and high temperature regions respectively. The operating mechanisms of work-hardening of the test alloys were confirmed by the analysis of X-ray diffraction patterns.

Research paper thumbnail of Effect of structure transformation on the creep characteristics of Sn–3wt% Bi alloy

Journal of Alloys and Compounds, 2007

... Nada [10] studied the effect of Pb-addition and irradiation with gamma rays on the mechanical... more ... Nada [10] studied the effect of Pb-addition and irradiation with gamma rays on the mechanical and thermal properties of Sn–5 wt% Bi alloys prepared by melt spinning technique. ... [8] GS Al-Ganainy, MR Nagy, BA Khalifa and R. Afifi, Phys. Stat. Sol. (a) 158 (1996), p. 463. ...