Medhat El-Hadek | Faculty Of Engineering Port Said University (original) (raw)
Papers by Medhat El-Hadek
International Journal of Solids and Structures, 2003
Functionally graded syntactic foam sheets are developed by dispersing microballoons in epoxy for ... more Functionally graded syntactic foam sheets are developed by dispersing microballoons in epoxy for studying dynamic fracture behavior under low velocity impact loading. The volume fraction of microballoons is graded linearly over the width of the sheets. The mode-I crack initiation and growth behaviors are studied using reflection coherent gradient sensing technique and high-speed photography in samples with crack on the compliant and stiff sides and oriented along the compositional gradient. Crack growth along the gradient in each case shows sudden acceleration followed by steady state growth and deceleration during the window of observation. In both cases, the crack accelerations are similar while crack decelerations show differences. The dynamic stress intensity factor history prior to crack initiation in each case shows a rapid increase at different rates with the crack on the compliant side of the graded sheet experiencing higher rate of loading relative to the one with the crack on the stiffer side. Post-crack initiation stress intensity factor histories suggest increasing fracture toughness with crack growth in the graded sample with the crack on the compliant side while a decreasing trend is seen when the crack is on the stiffer side. Optical measurements are supplemented by finite element simulations for studying crack tip constraint effects on fracture behavior of graded foam sheets. Computed plane strain constraints in graded configurations are essentially identical to the homogeneous counterpart and the computed stress intensity factors obtained from plane stress elastodynamic analyses of the graded foams correlate well with the experimental measurements prior to crack initiation. The computed T-stress histories however, show an earlier loss of negative crack tip constraint in case of the graded foam sample with a crack on the compliant side. This correlates well with the higher crack tip loading rate and earlier crack initiation suggesting a possible role of in-plane constraint on fracture of graded foam. The coincidence of the time rate of change of in-plane constraint parameter becoming stationary close to experimentally observed crack initiation times are noted.
The corrosion performance of carbon steel after wide-ranging acquaintance load of aqueous extract... more The corrosion performance of carbon steel after wide-ranging acquaintance load of aqueous extract of Lawsonia inermis (LI) as a green inhibitor in saline media was inspected. These studies have been supported by means of open-circuit potential (OCP), potentiodynamic polarization technique (PD) and electrochemical impedance spectroscopy (EIS). In addition, the scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis stayed applied as a complementary tool for surface characterization. For more illustration theoretical and statistical studies were subjected for corrosion inhibition efficiency. All results inveterate that, the carbon steel alloy corrosion rate decreases with the upsurge of inhibitor concentration and LI are an important deterrent for the saline solutions to corrosion of carbon steel alloy. The presence of LI particles anywhere decreased the cathodic, anodic and corrosion currents and the rate of deterioration, as well as improved polarization and so...
This study presents a comprehensive evaluation of Equal Channel Angular Pressing (ECAP) processin... more This study presents a comprehensive evaluation of Equal Channel Angular Pressing (ECAP) processing on the structural evolution and mechanical properties of AA2xxx aluminum alloy. Finite element analysis (FE) was used to study the deformation behavior of the AA2xxx billets during processing in addition investigate the strain homogeneity in the longitudinal and transverse direction. Billets of AA2011 aluminum alloy were processed successfully through ECAP up to 4-passes with rotating the sample 90° along its longitudinal axis in the same direction after each pass (route Bc) at 150 °C. The microstructural evolution and crystallographic texture were analyzed using the electron back-scatter diffraction (EBSD) and optical microscopy (OM). An evaluation of the hardness and tensile properties was presented and correlated with the EBSD findings and FE simulations. The FE analysis results were in good agreement with the experimental finding and microstructural evolution. Processing through 4-...
Advanced Materials Letters
The physical and mechanical properties of atomized prealloyed Fe-Cu powders, blended with differe... more The physical and mechanical properties of atomized prealloyed Fe-Cu powders, blended with different amounts of liquid additions of lead (Pb), were studied in the as-sintered condition and hot compaction techniques. The influence of Pb content, compacting pressure and temperature on the densification, hardness, and the mechanical properties were investigated. During hot compaction, at a temperature of 500°C, the Pb liquid was found to spread uniformly among Fe-Cu solid particles. The effect of pores in Fe-Cu-Pb alloys, generated by sintering with transient liquid phase, had been studied. An attempt was made in order to study the properties of Fe-Cu-Pb particles and their behaviour, with respect to the consolidation of Fe-Cu-Pb powders. The density values of cold and hot compacts, at various pressures and temperatures values, were reported. The microstructure, hardness, and strength measurements were found to be dependent upon the compacting pressure. For the cold compacted alloys, the Pb powder particles were completely melted to form liquid pools. In addition, increasing the Pb content in the alloy matrix revealed a decrease of the pores percentage, hence the sample became denser. On the other hand, grain was found to be coarser and less porosity is obtained with increasing the Pb content in the hot compacted. It is found that, increasing the compacting pressure of the cold and hot compacted samples revealed a homogenous, fine grain, and small pores appeared around the grain boundaries. The mechanical properties data showed improvement in the strength and hardness of the hot and cold compacted samples by increasing either the compaction pressure or temperature.
Journal de Physique …, 2004
Three-dimensional axisymmetric finite element analyses have been performed to analyze the coupled... more Three-dimensional axisymmetric finite element analyses have been performed to analyze the coupled thermo-mechanical oscillatory transient problem of friction welding of two dissimilar hollow cylinders. The analysis included the effect of conduction and convection heat transfer implementing three independent variables specifically the welding time, the rotational velocity, and the thrust pressure. Experimental evaluation of the non-linear copper and Aluminum 6061 stress-strain responses, the thermal conductivities, and the specific heat coefficients were conducted using an environmental-controlled compartment for at least four different temperatures. These results were incorporated in the finite element model calculating a real joint transient temperature distribution and a full field view of the residual stresses in weldment. Variables of angular rotational velocity of (200, 400, and 600 rpm), thrust pressure of (10E5, 10E6, and 10E7 Pa), and total welding time of (1, 2, and 4 seconds) were used in the model simulation. The optimum welding conditions were selected using Taguchi method. Finally, the deformation shape predicted by the finite element simulations was compared to the deformations obtained by the experimental results.
Detailed micro electronic and mechanical systems (MEMS) for a mobile microprocessor complex shape... more Detailed micro electronic and mechanical systems (MEMS) for a mobile microprocessor complex shape were modeled using Finite Element (FE) processing. Fatigue and impact conditions were performed on the Ball Grid Array (BGA) Integrated Circuit (IC) using Abaqus\CAE finite element analysis software. The main objective of this research is to make sure that BGA products can endure the roughness of the daily usage, where a portable electronic product is habitually coupled with potential damage of functional failure when the device falls.
Metals
Functionally-graded materials (FGM) have recently been widely used. Furthermore, FGM are widely r... more Functionally-graded materials (FGM) have recently been widely used. Furthermore, FGM are widely recommended in cylinder design. This study represents a mathematical analysis of the stresses and strains of an FGM cylinder. The paper is interested in introducing a stress analysis to an FGM cylinder where its properties vary exponentially in the r-direction. Firstly, a benchwork has been done and compared with recent works in the same field. The radial stress, the hoop stress, and the longitudinal stress on a cylinder under mechanical and thermal loading have been theoretically derived. In addition, a finite element analysis has been investigated through ANSYS software. Finally, the values of stresses obtained from the derived equations and the corresponding values of stresses obtained from ANSYS have been compared. The obtained results established the efficiency of the proposed stress distribution and the optimization model in this research, which would be helpful for understanding we...
Advanced Materials Letters
In this study, elemental Cu and Sn powder were mechanically mixed forming different Cu-Sn alloys.... more In this study, elemental Cu and Sn powder were mechanically mixed forming different Cu-Sn alloys. To ensure uniformity of the particle shapes, the Cu, and Sn were mechanically milled and mixed in an agate rock mortar, with high energy ball mill for half an hour, with different weight ratios according to the composition design. The milling of the powders resulted in uniform sphere-like particles for Cu–Sn alloys. Hot compaction was performed in a single acting piston cylinder arrangement at room temperature. All hot pressed MMCs were heat-treated at about 550C to allow the atoms to diffuse randomly into a uniform solid solution, as liquid phase sintering. Vickers micro-hardness measurements were carried out for the hot-pressed Cu–Sn alloys. Cylindrical specimens of aspect ratio of ho/do = 1.5 were tested under frictionless conditions at the compression platen interface. Charpy transverse rupture strength had been used to determine the fracture strength of the different Cu-Sn alloys. Fracture surface features of the different Cu-Sn alloys were characterized using scanning electron microscopy. It had been found that, the 85%Cu–15% Sn alloy revealed an increase of hardness values, a decrease of the yield strength, and an increase in the impact energy by 26.2, 23, and 18.7%; respectively, compared with the Sn-free alloy. The Cu-Sn alloys showed an apparently classical inclined fracture surface, at about 45 o with the applied stress axis, which was similar to what's obtained for a diversity of hard metals.
Iron powders having average particle sizes of ~40µm are mechanically mixed thoroughly with ... more Iron powders having average particle sizes of ~40µm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt.% with an average particle size of ~10µm. Two different powder metallurgical techniques cold and hot pressing are used to study the effect of the additive element powder on the mechanical properties, wear properties and the microstructure of the iron based alloys. The hot pressing technique was performed at a temperature up to 500°C at 445.6 MPa. The cold pressing technique was performed at 909 MPa in room temperature. By increasing the Al content to 10 wt. % in the base Fe-based matrix, the hardness was decreased from 780 to 690 MPa and the radial strength was decreased from 380 to 202 MPa with reductions of 11.5% and 40%, respectively. Improvement of the wear resistance with the increase addition of the Al powder to the Fe matrix up to 5 times was achieved compared to the alloy without Al addition for different wear parameters namel...
Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and hea... more Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and heat treated powder metallurgy. Cr addition ranged between 5 to 10 wt. % while Zn was added in an amount between 0 to 20 wt. %. Heat treatment processes were performed during powder metallurgy process at different temperatures followed by water quenching. Similar alloys were extruded, with an extrusion ratio of 4.6 to get proper densification. Optical microscopy was used for microstructure investigations of the produced alloys. The element distribution microstructure study was carried out using the Energy Dispersive X-ray analysis method. Hardness and tensile properties of the investigated alloys have been examined. Wear resistance tests were carried out and the results were compared with these of the Al-based bulk alloys. Results showed that the aluminum base alloys containing 10wt. % Chromium and heat treated at 500°C for one hour followed by water quenching exhibited the highest wear...
Journal of Thermal Analysis and Calorimetry, 2000
Engine Viking of Ariane 4 is supplied with asymmetrical dimethylhydrazine (UDMH) (CH3)2NNH2. An a... more Engine Viking of Ariane 4 is supplied with asymmetrical dimethylhydrazine (UDMH) (CH3)2NNH2. An addition of a small amount of hydrazine hydrate N2H4H2O was proposed to increase the thermal stability of UDMH. The mixture where the mass ratio (CH3)2NNH2/N2H4H2O is equals to 75/25, is called UH25. These propelling agents are unstable when they are heated and the optimisation of burning conditions
Powder injection molding (PIM) is an interesting technique and address of research, in which a th... more Powder injection molding (PIM) is an interesting technique and address of research, in which a thermoplastic polymeric material is used to form the powder into the desired shape in a closed die. Binders have a crucial importance in the powder metallurgy technology as they play a vital role to provide efficient powder agglomeration and/or lubrication during shaping. At the same time, they have to be easily removed from the compacts during initial stages of sintering, using debinding process, without any damaging effect for the base material. Thermal debinding is a vital process requiring somewhat elevated temperatures to remove binder from the compact. In the current study, an investigation has been made about the effect of process variables on the debinding of injection molded pieces, by melt wicking. The debinding process was performed at temperatures ranging from 160-up to-200°C for a time duration varying from 1-up to-27 hours. All powders used in injection molding feedstock have...
The International Journal of Advanced Manufacturing Technology, 2014
Aluminum powder with an average particle size of 10 μm was mechanically mixed thoroughly with 5 w... more Aluminum powder with an average particle size of 10 μm was mechanically mixed thoroughly with 5 wt% fine Al 2 O 3 powder with an average particle size of 3.7 μm reinforcement. Iron particles with an average particle size of 0.5 nm and copper particle size of 10 μm were added to the base matrix Al-5Al 2 O 3 . The composite material was produced by a single action hot compaction of the powders. Aluminum-alumina composites containing iron, copper, and iron with copper were produced through mixing the atomized matrix alloy powder with 5 wt% of Al 2 O 3 particles, then cold pressed for 5 min, degaussed, and hot pressed. The hot pressing technique was performed up to 500°C at 318.34 MPa for 5 min dwell time. The Al-5Al 2 O 3 composites were examined for hardness, compression flow properties, and wear analysis.
Advances in Materials Science and Engineering, 2016
Cu-Sn based alloy powders with additives of elemental Pb or C were densified by hot pressing tech... more Cu-Sn based alloy powders with additives of elemental Pb or C were densified by hot pressing technique. The influence of densifying on the properties of the hot pressed materials was investigated. The properties, such as the hardness, compressive strength, and wear resistance of these materials, were determined. The hot pressed Cu-Sn specimens included intermetallic/phases, which were homogeneously distributed. The presence of graphite improved the wear resistance of Cu-Sn alloys three times. Similarly, the presence of lead improved the densification parameter of Cu-Sn alloys three times. There was no significant difference in the mechanical behavior associated with the addition of Pb to the Cu-Sn alloys, although Cu-Pb alloys showed considerably higher ultimate strength and higher elongation. The Cu-Sn-C alloys had lower strength compared with those of Cu-Sn alloys. Evidence of severe melting spots was noticed in the higher magnifications of the compression fracture surface of 85% Cu-10% Sn-5% C and 80% Cu-10% Sn-10% Pb alloys. This was explained by the release of load at the final event of the fracture limited area.
Dynamic crack initiation and growth in functionally graded syntactic epoxy foams were studied und... more Dynamic crack initiation and growth in functionally graded syntactic epoxy foams were studied under low-velocity impact loading conditions. Foam sheets with nearly linear variation of volume fraction of microballoons in the range 0 to 45% were prepared. Crack initiation and growth in situations when cracks were located on the compliant and stiffer sides the graded sheets subjected to symmetric single point impact was studied separately. The transient crack tip deformations were measured using the optical technique of Coherent Gradient Sensing (CGS) in conjunction with high-speed photography. Dynamic stress intensity factor histories corresponding to pre-and post-crack initiation and crack growth histories were analyzed using optical interferograms. The influence of the compositional grading of microballoons in the matrix has been quantified. Introduction Syntactic foams can be distinguished from conventional foams in the way they are manufactured namely by mechanically blending thin...
International Journal of Solids and Structures, 2003
Functionally graded syntactic foam sheets are developed by dispersing microballoons in epoxy for ... more Functionally graded syntactic foam sheets are developed by dispersing microballoons in epoxy for studying dynamic fracture behavior under low velocity impact loading. The volume fraction of microballoons is graded linearly over the width of the sheets. The mode-I crack initiation and growth behaviors are studied using reflection coherent gradient sensing technique and high-speed photography in samples with crack on the compliant and stiff sides and oriented along the compositional gradient. Crack growth along the gradient in each case shows sudden acceleration followed by steady state growth and deceleration during the window of observation. In both cases, the crack accelerations are similar while crack decelerations show differences. The dynamic stress intensity factor history prior to crack initiation in each case shows a rapid increase at different rates with the crack on the compliant side of the graded sheet experiencing higher rate of loading relative to the one with the crack on the stiffer side. Post-crack initiation stress intensity factor histories suggest increasing fracture toughness with crack growth in the graded sample with the crack on the compliant side while a decreasing trend is seen when the crack is on the stiffer side. Optical measurements are supplemented by finite element simulations for studying crack tip constraint effects on fracture behavior of graded foam sheets. Computed plane strain constraints in graded configurations are essentially identical to the homogeneous counterpart and the computed stress intensity factors obtained from plane stress elastodynamic analyses of the graded foams correlate well with the experimental measurements prior to crack initiation. The computed T-stress histories however, show an earlier loss of negative crack tip constraint in case of the graded foam sample with a crack on the compliant side. This correlates well with the higher crack tip loading rate and earlier crack initiation suggesting a possible role of in-plane constraint on fracture of graded foam. The coincidence of the time rate of change of in-plane constraint parameter becoming stationary close to experimentally observed crack initiation times are noted.
The corrosion performance of carbon steel after wide-ranging acquaintance load of aqueous extract... more The corrosion performance of carbon steel after wide-ranging acquaintance load of aqueous extract of Lawsonia inermis (LI) as a green inhibitor in saline media was inspected. These studies have been supported by means of open-circuit potential (OCP), potentiodynamic polarization technique (PD) and electrochemical impedance spectroscopy (EIS). In addition, the scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis stayed applied as a complementary tool for surface characterization. For more illustration theoretical and statistical studies were subjected for corrosion inhibition efficiency. All results inveterate that, the carbon steel alloy corrosion rate decreases with the upsurge of inhibitor concentration and LI are an important deterrent for the saline solutions to corrosion of carbon steel alloy. The presence of LI particles anywhere decreased the cathodic, anodic and corrosion currents and the rate of deterioration, as well as improved polarization and so...
This study presents a comprehensive evaluation of Equal Channel Angular Pressing (ECAP) processin... more This study presents a comprehensive evaluation of Equal Channel Angular Pressing (ECAP) processing on the structural evolution and mechanical properties of AA2xxx aluminum alloy. Finite element analysis (FE) was used to study the deformation behavior of the AA2xxx billets during processing in addition investigate the strain homogeneity in the longitudinal and transverse direction. Billets of AA2011 aluminum alloy were processed successfully through ECAP up to 4-passes with rotating the sample 90° along its longitudinal axis in the same direction after each pass (route Bc) at 150 °C. The microstructural evolution and crystallographic texture were analyzed using the electron back-scatter diffraction (EBSD) and optical microscopy (OM). An evaluation of the hardness and tensile properties was presented and correlated with the EBSD findings and FE simulations. The FE analysis results were in good agreement with the experimental finding and microstructural evolution. Processing through 4-...
Advanced Materials Letters
The physical and mechanical properties of atomized prealloyed Fe-Cu powders, blended with differe... more The physical and mechanical properties of atomized prealloyed Fe-Cu powders, blended with different amounts of liquid additions of lead (Pb), were studied in the as-sintered condition and hot compaction techniques. The influence of Pb content, compacting pressure and temperature on the densification, hardness, and the mechanical properties were investigated. During hot compaction, at a temperature of 500°C, the Pb liquid was found to spread uniformly among Fe-Cu solid particles. The effect of pores in Fe-Cu-Pb alloys, generated by sintering with transient liquid phase, had been studied. An attempt was made in order to study the properties of Fe-Cu-Pb particles and their behaviour, with respect to the consolidation of Fe-Cu-Pb powders. The density values of cold and hot compacts, at various pressures and temperatures values, were reported. The microstructure, hardness, and strength measurements were found to be dependent upon the compacting pressure. For the cold compacted alloys, the Pb powder particles were completely melted to form liquid pools. In addition, increasing the Pb content in the alloy matrix revealed a decrease of the pores percentage, hence the sample became denser. On the other hand, grain was found to be coarser and less porosity is obtained with increasing the Pb content in the hot compacted. It is found that, increasing the compacting pressure of the cold and hot compacted samples revealed a homogenous, fine grain, and small pores appeared around the grain boundaries. The mechanical properties data showed improvement in the strength and hardness of the hot and cold compacted samples by increasing either the compaction pressure or temperature.
Journal de Physique …, 2004
Three-dimensional axisymmetric finite element analyses have been performed to analyze the coupled... more Three-dimensional axisymmetric finite element analyses have been performed to analyze the coupled thermo-mechanical oscillatory transient problem of friction welding of two dissimilar hollow cylinders. The analysis included the effect of conduction and convection heat transfer implementing three independent variables specifically the welding time, the rotational velocity, and the thrust pressure. Experimental evaluation of the non-linear copper and Aluminum 6061 stress-strain responses, the thermal conductivities, and the specific heat coefficients were conducted using an environmental-controlled compartment for at least four different temperatures. These results were incorporated in the finite element model calculating a real joint transient temperature distribution and a full field view of the residual stresses in weldment. Variables of angular rotational velocity of (200, 400, and 600 rpm), thrust pressure of (10E5, 10E6, and 10E7 Pa), and total welding time of (1, 2, and 4 seconds) were used in the model simulation. The optimum welding conditions were selected using Taguchi method. Finally, the deformation shape predicted by the finite element simulations was compared to the deformations obtained by the experimental results.
Detailed micro electronic and mechanical systems (MEMS) for a mobile microprocessor complex shape... more Detailed micro electronic and mechanical systems (MEMS) for a mobile microprocessor complex shape were modeled using Finite Element (FE) processing. Fatigue and impact conditions were performed on the Ball Grid Array (BGA) Integrated Circuit (IC) using Abaqus\CAE finite element analysis software. The main objective of this research is to make sure that BGA products can endure the roughness of the daily usage, where a portable electronic product is habitually coupled with potential damage of functional failure when the device falls.
Metals
Functionally-graded materials (FGM) have recently been widely used. Furthermore, FGM are widely r... more Functionally-graded materials (FGM) have recently been widely used. Furthermore, FGM are widely recommended in cylinder design. This study represents a mathematical analysis of the stresses and strains of an FGM cylinder. The paper is interested in introducing a stress analysis to an FGM cylinder where its properties vary exponentially in the r-direction. Firstly, a benchwork has been done and compared with recent works in the same field. The radial stress, the hoop stress, and the longitudinal stress on a cylinder under mechanical and thermal loading have been theoretically derived. In addition, a finite element analysis has been investigated through ANSYS software. Finally, the values of stresses obtained from the derived equations and the corresponding values of stresses obtained from ANSYS have been compared. The obtained results established the efficiency of the proposed stress distribution and the optimization model in this research, which would be helpful for understanding we...
Advanced Materials Letters
In this study, elemental Cu and Sn powder were mechanically mixed forming different Cu-Sn alloys.... more In this study, elemental Cu and Sn powder were mechanically mixed forming different Cu-Sn alloys. To ensure uniformity of the particle shapes, the Cu, and Sn were mechanically milled and mixed in an agate rock mortar, with high energy ball mill for half an hour, with different weight ratios according to the composition design. The milling of the powders resulted in uniform sphere-like particles for Cu–Sn alloys. Hot compaction was performed in a single acting piston cylinder arrangement at room temperature. All hot pressed MMCs were heat-treated at about 550C to allow the atoms to diffuse randomly into a uniform solid solution, as liquid phase sintering. Vickers micro-hardness measurements were carried out for the hot-pressed Cu–Sn alloys. Cylindrical specimens of aspect ratio of ho/do = 1.5 were tested under frictionless conditions at the compression platen interface. Charpy transverse rupture strength had been used to determine the fracture strength of the different Cu-Sn alloys. Fracture surface features of the different Cu-Sn alloys were characterized using scanning electron microscopy. It had been found that, the 85%Cu–15% Sn alloy revealed an increase of hardness values, a decrease of the yield strength, and an increase in the impact energy by 26.2, 23, and 18.7%; respectively, compared with the Sn-free alloy. The Cu-Sn alloys showed an apparently classical inclined fracture surface, at about 45 o with the applied stress axis, which was similar to what's obtained for a diversity of hard metals.
Iron powders having average particle sizes of ~40µm are mechanically mixed thoroughly with ... more Iron powders having average particle sizes of ~40µm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt.% with an average particle size of ~10µm. Two different powder metallurgical techniques cold and hot pressing are used to study the effect of the additive element powder on the mechanical properties, wear properties and the microstructure of the iron based alloys. The hot pressing technique was performed at a temperature up to 500°C at 445.6 MPa. The cold pressing technique was performed at 909 MPa in room temperature. By increasing the Al content to 10 wt. % in the base Fe-based matrix, the hardness was decreased from 780 to 690 MPa and the radial strength was decreased from 380 to 202 MPa with reductions of 11.5% and 40%, respectively. Improvement of the wear resistance with the increase addition of the Al powder to the Fe matrix up to 5 times was achieved compared to the alloy without Al addition for different wear parameters namel...
Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and hea... more Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and heat treated powder metallurgy. Cr addition ranged between 5 to 10 wt. % while Zn was added in an amount between 0 to 20 wt. %. Heat treatment processes were performed during powder metallurgy process at different temperatures followed by water quenching. Similar alloys were extruded, with an extrusion ratio of 4.6 to get proper densification. Optical microscopy was used for microstructure investigations of the produced alloys. The element distribution microstructure study was carried out using the Energy Dispersive X-ray analysis method. Hardness and tensile properties of the investigated alloys have been examined. Wear resistance tests were carried out and the results were compared with these of the Al-based bulk alloys. Results showed that the aluminum base alloys containing 10wt. % Chromium and heat treated at 500°C for one hour followed by water quenching exhibited the highest wear...
Journal of Thermal Analysis and Calorimetry, 2000
Engine Viking of Ariane 4 is supplied with asymmetrical dimethylhydrazine (UDMH) (CH3)2NNH2. An a... more Engine Viking of Ariane 4 is supplied with asymmetrical dimethylhydrazine (UDMH) (CH3)2NNH2. An addition of a small amount of hydrazine hydrate N2H4H2O was proposed to increase the thermal stability of UDMH. The mixture where the mass ratio (CH3)2NNH2/N2H4H2O is equals to 75/25, is called UH25. These propelling agents are unstable when they are heated and the optimisation of burning conditions
Powder injection molding (PIM) is an interesting technique and address of research, in which a th... more Powder injection molding (PIM) is an interesting technique and address of research, in which a thermoplastic polymeric material is used to form the powder into the desired shape in a closed die. Binders have a crucial importance in the powder metallurgy technology as they play a vital role to provide efficient powder agglomeration and/or lubrication during shaping. At the same time, they have to be easily removed from the compacts during initial stages of sintering, using debinding process, without any damaging effect for the base material. Thermal debinding is a vital process requiring somewhat elevated temperatures to remove binder from the compact. In the current study, an investigation has been made about the effect of process variables on the debinding of injection molded pieces, by melt wicking. The debinding process was performed at temperatures ranging from 160-up to-200°C for a time duration varying from 1-up to-27 hours. All powders used in injection molding feedstock have...
The International Journal of Advanced Manufacturing Technology, 2014
Aluminum powder with an average particle size of 10 μm was mechanically mixed thoroughly with 5 w... more Aluminum powder with an average particle size of 10 μm was mechanically mixed thoroughly with 5 wt% fine Al 2 O 3 powder with an average particle size of 3.7 μm reinforcement. Iron particles with an average particle size of 0.5 nm and copper particle size of 10 μm were added to the base matrix Al-5Al 2 O 3 . The composite material was produced by a single action hot compaction of the powders. Aluminum-alumina composites containing iron, copper, and iron with copper were produced through mixing the atomized matrix alloy powder with 5 wt% of Al 2 O 3 particles, then cold pressed for 5 min, degaussed, and hot pressed. The hot pressing technique was performed up to 500°C at 318.34 MPa for 5 min dwell time. The Al-5Al 2 O 3 composites were examined for hardness, compression flow properties, and wear analysis.
Advances in Materials Science and Engineering, 2016
Cu-Sn based alloy powders with additives of elemental Pb or C were densified by hot pressing tech... more Cu-Sn based alloy powders with additives of elemental Pb or C were densified by hot pressing technique. The influence of densifying on the properties of the hot pressed materials was investigated. The properties, such as the hardness, compressive strength, and wear resistance of these materials, were determined. The hot pressed Cu-Sn specimens included intermetallic/phases, which were homogeneously distributed. The presence of graphite improved the wear resistance of Cu-Sn alloys three times. Similarly, the presence of lead improved the densification parameter of Cu-Sn alloys three times. There was no significant difference in the mechanical behavior associated with the addition of Pb to the Cu-Sn alloys, although Cu-Pb alloys showed considerably higher ultimate strength and higher elongation. The Cu-Sn-C alloys had lower strength compared with those of Cu-Sn alloys. Evidence of severe melting spots was noticed in the higher magnifications of the compression fracture surface of 85% Cu-10% Sn-5% C and 80% Cu-10% Sn-10% Pb alloys. This was explained by the release of load at the final event of the fracture limited area.
Dynamic crack initiation and growth in functionally graded syntactic epoxy foams were studied und... more Dynamic crack initiation and growth in functionally graded syntactic epoxy foams were studied under low-velocity impact loading conditions. Foam sheets with nearly linear variation of volume fraction of microballoons in the range 0 to 45% were prepared. Crack initiation and growth in situations when cracks were located on the compliant and stiffer sides the graded sheets subjected to symmetric single point impact was studied separately. The transient crack tip deformations were measured using the optical technique of Coherent Gradient Sensing (CGS) in conjunction with high-speed photography. Dynamic stress intensity factor histories corresponding to pre-and post-crack initiation and crack growth histories were analyzed using optical interferograms. The influence of the compositional grading of microballoons in the matrix has been quantified. Introduction Syntactic foams can be distinguished from conventional foams in the way they are manufactured namely by mechanically blending thin...