Nahed El-mahallawy - Academia.edu (original) (raw)

Papers by Nahed El-mahallawy

Research paper thumbnail of Coupled heat and fluid flow model and experimental verification of aluminium plate die casting

Materials Science and Technology, 2009

ABSTRACT The present work aims to forecast mould filling, void shape, location and size as well a... more ABSTRACT The present work aims to forecast mould filling, void shape, location and size as well as columnar to equiaxed transition (CET) in commercial pure aluminium casting. A model coupling the momentum equations of the fluid flow and heat transfer equations is presented, in which metallostatic pressure, air gap and oxide layer are considered. Different casting parameters were investigated such as casting configuration by varying the plate thickness from 5 to 20 mm, melt superheat from 40 to 120°C, mould preheat up to 200°C and different pouring heads ranging from 0·3 to 0·6 m. Regarding the microstructure and void formation, the approach based on the Niyama criterion, was considered. The experimental verification of the model was achieved by gravity die casting in the form of a rectangular cavity. Voids inside aluminium plate were investigated by X-ray imaging. Microstructure and CET was investigated microscopically. The supposed model proves its validity for mould filling and in detecting the void features and CET.

Research paper thumbnail of Machinability characteristics of lead free-silicon brass alloys as correlated with microstructure and mechanical properties

Ain Shams Engineering Journal, 2012

The aim of this work is to evaluate the machinability of Pb-free brasses with Si from 1% to 4 wt%... more The aim of this work is to evaluate the machinability of Pb-free brasses with Si from 1% to 4 wt%, which were prepared using Cu 60/Zn 40 and Cu 80/Si 20 Pb-free master alloys. Machinability of the investigated alloys is tested based on cutting force, tool wear, surface roughness, and chip type. In the 1 wt% Si alloy, which exhibits maximum strength, the maximum cutting force is measured and undesirable continuous chip type is produced, while tool wear and machined surface roughness have the lowest values. Increasing the silicon content from 1% to 4%, results in increasing the tool wear by 140%, machined surface roughness by 25%, while the chip type changed from continuous to discontinuous type, and the cutting force was reduced by 50%. Machinability results are correlated with the alloy mechanical properties and with the phases present in the microstructure.

Research paper thumbnail of Cold Compaction of Al-Zn Powder Composite Materials

Key Engineering Materials, 1993

... Figure (3.b) shows that increasing compaction load raises the reltive density for all particl... more ... Figure (3.b) shows that increasing compaction load raises the reltive density for all particle sizes and that the finner ps corresponds to the higher relative density. Figure (4), supports the same result in a relationship between specimen height and compaction load. Page 4. ...

Research paper thumbnail of Prediction of Hypoeutectic Gray Iron Microstructure during Solidification and Solid Transformation Using Simple Fourier Model

Abstract Phases' evolution during the solidification of a hypoeutectic 3.92% C-equivalen... more Abstract Phases' evolution during the solidification of a hypoeutectic 3.92% C-equivalence cast iron was modelled by considering the cooling history of the alloy from the melt, thus including both solidification and solid state transformations. Simple Fourier model was ...

Research paper thumbnail of Solidification Simulation of Equiaxed Grains in Al - Si Eutectic Alloys

Materials Science Forum, 1996

Page 1. Materials Science Forum Vols. 217-222 (1996) pp 347-352 © (1996) Trans Tech Publications,... more Page 1. Materials Science Forum Vols. 217-222 (1996) pp 347-352 © (1996) Trans Tech Publications, Switzerland doi: 10.4028/www. scientific. net/MSF. 217-222.34 7 Solidification Simulation of Equiaxed Grains in Al - Si Eutectic ...

Research paper thumbnail of Relationship between formability and cast structures in end-chill directionally solidified Al–Cu alloys

Materials & Design, 2002

End-chill unidirectional solidification experiments have been conducted on pure Al and Al᎐Cu allo... more End-chill unidirectional solidification experiments have been conducted on pure Al and Al᎐Cu alloys with 1, 3 and 4.5 wt.% Cu, using melt superheat varying between 50 and 200 K. The specimens produced were 50 mm in diameter and 150᎐200 mm long. Studying the solidification structure indicated that most of the specimens exhibited a columnar structure growing perpendicular to the chill surface, followed by equiaxed grains. The volume fraction of the columnar structure and the grain size of the equiaxed one are related to the Cu content, superheat and the cooling rate. The volume fraction of the eutectic phase varied, depending on the casting parameters. Compression testing has been performed, in order to study the formability of the columnar and equiaxed Ž . grain structures. Constant testing conditions of a specimen slenderness ratio 8: 8 and strain rate of 1 mmrs were used, as well as a lubricant. In the relationship s k n , describing the true stressrtrue strain relationship for the region between the limits of Ž . Ž . initial yielding and necking in ductile materials, the strength coefficient k and strain hardening coefficient n are used as indices for formability. Hence, the difference in formability behaviour between the columnar and equiaxed grains is presented. ᮊ

Research paper thumbnail of Tungsten-Reinforced Niobium Intermetallic Composites: Fabrication and Interface Reaction

Key Engineering Materials, 1993

Research paper thumbnail of Structural response to shape variations in the AI-AI3Ni eutectic composite

Metallurgical Transactions A, 1979

Page 1. Structural Response to Shape Variations in the AI-AI3Ni Eutectic Composite NAHED A. EL-MA... more Page 1. Structural Response to Shape Variations in the AI-AI3Ni Eutectic Composite NAHED A. EL-MAHALLAWYAND MAHMOUD M. FARAG Structural irregularities that arise due to shape variations in A1-A13Ni directionally solidified eutectic composites have been analyzed. ...

Research paper thumbnail of Microstructure of In-Situ composites

Materialwissenschaft und Werkstofftechnik, 1983

ABSTRACT

Research paper thumbnail of Morphological variations in melt-spun AlCu alloys

Materials Science and Engineering: A, 1991

Research paper thumbnail of On the technological properties of steel strips aluminized in Al-Si baths

Journal of Materials Science Letters, 1996

... Mer. Finishing 80 (1980) 21. 4. H. LUDWIG, E. ULRICH and W. WILHELM, Prakt. Metallogr. 31 (19... more ... Mer. Finishing 80 (1980) 21. 4. H. LUDWIG, E. ULRICH and W. WILHELM, Prakt. Metallogr. 31 (1994) 78. 5. MA SHADY, AR EL-SISSI, MA ATTIA, NA EL-MAHALLAWY,MA TAHA and W. REIF, J. Mar. Sei. TechnoL, submitted. 6 ...

Research paper thumbnail of Simulations and experiments in pressurized solidification process (PSP) and rapid solidification process (RSP)

Journal of Materials Science Letters, 1985

The present work shows numerical models and experiments in two solidification processes: pressuri... more The present work shows numerical models and experiments in two solidification processes: pressurized solidification (PSP) and rapid solidification (RSP). In PSP, the application of pressure leads to higher cooling rates due to the minimization of air gap at the metal/mould interface. In RSP, the high cooling rates obtained are function of the process parameters like melt superheat, wheel material, temperature and velocity and the surrounding atmosphere.

Research paper thumbnail of Metal-mould heat transfer coefficient using end-chill experiments

Journal of Materials Science Letters, 1988

In several casting processes, directional solidification by the use of end-chill is used to produ... more In several casting processes, directional solidification by the use of end-chill is used to produce steep temperature gradients within the casting. Mathematical modelling or computer simulation of solidification has proved to be a powerful tool for process control and optimization of parameters in several areas . For the computer simulation to be accurate, several thermal data are needed. Besides the thermal properties of the materials in use, information about metal-mould heat transfer coefficients and convection in the melt are needed .

Research paper thumbnail of Effect of melt superheat on heat transfer coefficient for aluminium solidifying against copper chill

Journal of Materials Science, 1991

Solidification of metal castings inside moulds is mainly dependent on the heat flow from the meta... more Solidification of metal castings inside moulds is mainly dependent on the heat flow from the metal to the mould which is in turn proportional to an overall heat transfer coefficient h which includes all resistances to heat flow such as the presence of an air gap. In the present work the heat transfer coefficient is determined using a directional solidification set-up with end chill for solidifying commercial-purity aluminium with different superheats (40 K and 115 K) against copper chill. A computer program solving the heat conduction and convection in the solidifying metal is used together with the experimental temperature history in order to determine the heat transfer coefficient at the interface. The variation of h as a function of time, surface temperature and gap temperature for each melt superheat is found. The results indicate that h reaches a maximum value for surface temperature close to the liquidus. The analysis of heat flux from the metal to the mould indicates that it is mainly by conduction. The air gap size is evaluated with time, surface temperature and with melt superheat. It is found that higher h values and smaller gap sizes are obtained with higher superheats.

Research paper thumbnail of Effect of melt superheat and chill material on interfacial heat-transfer coefficient in end-chill Al and Al-Cu alloy castings

Journal of Materials Science, 1992

Solidification of metal castings inside moulds is mainly dependent on the rate of heat removal fr... more Solidification of metal castings inside moulds is mainly dependent on the rate of heat removal from the metal to the mould. During casting solidification, an air gap usually develops at the interface between the solidfying metal and the surrounding mould or chill. This condition occurs in most casting geometries, except in some cases such as the cast metal solidifying around a central core. An overall heat-transfer coefficient, which includes all resistances to heat flow from the metal to its surroundings can be determined. The objective of this work was to determine the overall heat-transfer coefficient,h, using experimental and computersimulation results on commercial purity aluminium and Al-4.5 wt% Cu alloy solidifying in a vertical end-chill apparatus. The cast ingots had a cylindrical shape with 12.5 mm diameter and different lengths of 95 and 230 mm. It solidified at different superheats (ranging from 50–110 °C) against two different chill materials: copper, and dry moulding sand. A computer program solving the heat-conduction equation and taking into consideration the convection in the melt, was used to compute the temperature history at numerous points along the ingot length. Differenth values were assumed as a function of time, until agreement between experimental and computed cooling curves was obtained. The variation ofh as a function of time, surface temperature, specimen length for each melt superheat and chill material was found. The thickness of the air gap was also evaluated. The results indicate that the variation of heat-transfer coefficient with time followed a pattern of sudden increase for the first few seconds, followed by a steady state, after whichh decreased and reached another lower constant value. Theh values were also found to decrease rapidly when the liquidus temperature was reached in the melt. For longer specimen and higher melt superheat, the heat-transfer coefficient increased. It was also higher for a copper than for a sand chill.

Research paper thumbnail of Control of the continuous rheocasting process

Journal of Materials Science, 1988

In the continuous rheocasting process, a semi-solid alloy is obtained from the exit port of the a... more In the continuous rheocasting process, a semi-solid alloy is obtained from the exit port of the apparatus at a given rate and with a given fraction of solid. This solid fraction is dependent on the corresponding temperature within the solid-liquid range which should be controlled accurately by the process parameters for a given rheocaster stirring chamber. For this purpose a heat flow model has been established for the continuous rheocasting of Bi-17 wt% Sn alloy. The heat transfer calculations are based on the solution of the two-dimensional partial differential equations using a finite difference method. An excellent agreement between calculations and experimental results is found. Computations are carried out in order to find the influence of stirring chamber dimensions on the alloy exit temperature and therefore, the volume fraction of solid. The influence of input metal temperature and metal flow rate on the exit temperature and volume fraction of solid are also found.

Research paper thumbnail of Surface roughness and mechanical properties of melt-spun Al-Cu ribbons

Journal of Materials Science, 1992

AI, and AI-33wt% Cu ribbons with different thicknesses, t, have been prepared by chilled block me... more AI, and AI-33wt% Cu ribbons with different thicknesses, t, have been prepared by chilled block melt spinning under different processing conditions. Surface roughness, taken as peak to valley values, Rt, measured on both the substrate and air sides of the ribbon, shows great dependence on substrate velocity, v, ejection gas pressure, P, nozzle height above the substrate, H, and a lesser dependence on substrate thermal conductivity, k, and melt superheat, AT. The bulk density over all the zones shows an increase over conventionally cast alloys of 7.4% for AI-33 wt% Cu and about 3% for aluminium. Microhardness, Hn, measurements inside each of the three microstructure zones, which were identified across the ribbon section, show variation with t as Hn = Ho t-m, where the constant H o depends on the microstructure zone and m depends on the alloy composition. The zone at the substrate side has the highest Ha values and that at the air side has the lowest ones. The number of bending cycles to fracture, which is taken as a measure of ductility, increased with ribbon thickness and decreased with copper content.

Research paper thumbnail of On crack susceptibility in the submerged arc welding of medium-carbon steel plates

Journal of Materials Processing Technology, 1997

Research paper thumbnail of Workability of unidirectionally solidified Al-8 wt% Cu alloy: Part I. Cold workability

Journal of Materials Processing Technology, 1992

The cold workability of unidirectionally solidified commercial A1-8 wt% Cu alloy is studied using... more The cold workability of unidirectionally solidified commercial A1-8 wt% Cu alloy is studied using the cold-upsetting test in the axial direction of the specimens. A constant temperature gradient and different growth rates were used to produce an arrayed dendritic morphology with different sizes. Different friction conditions and aspect ratios were used in the tests. The influence of the structure size and the upsetting conditions on the limiting strains, the limiting reduction in height and the forming-limit lines are presented. The cracks formed on the barreled surface of the specimens are examined.

Research paper thumbnail of Some experimental data on workability of aluminium-particulate-reinforced metal matrix composites

Journal of Materials Processing Technology, 2008

... composites. Mohamed A. Taha Corresponding Author Contact Information , a , E-mail The Corresp... more ... composites. Mohamed A. Taha Corresponding Author Contact Information , a , E-mail The Corresponding Author , Nahed A. El-Mahallawy a and Ahmed M. El-Sabbagh a. a Faculty of Engineering, Ain-Shams University, Cairo, Egypt. ...

Research paper thumbnail of Coupled heat and fluid flow model and experimental verification of aluminium plate die casting

Materials Science and Technology, 2009

ABSTRACT The present work aims to forecast mould filling, void shape, location and size as well a... more ABSTRACT The present work aims to forecast mould filling, void shape, location and size as well as columnar to equiaxed transition (CET) in commercial pure aluminium casting. A model coupling the momentum equations of the fluid flow and heat transfer equations is presented, in which metallostatic pressure, air gap and oxide layer are considered. Different casting parameters were investigated such as casting configuration by varying the plate thickness from 5 to 20 mm, melt superheat from 40 to 120°C, mould preheat up to 200°C and different pouring heads ranging from 0·3 to 0·6 m. Regarding the microstructure and void formation, the approach based on the Niyama criterion, was considered. The experimental verification of the model was achieved by gravity die casting in the form of a rectangular cavity. Voids inside aluminium plate were investigated by X-ray imaging. Microstructure and CET was investigated microscopically. The supposed model proves its validity for mould filling and in detecting the void features and CET.

Research paper thumbnail of Machinability characteristics of lead free-silicon brass alloys as correlated with microstructure and mechanical properties

Ain Shams Engineering Journal, 2012

The aim of this work is to evaluate the machinability of Pb-free brasses with Si from 1% to 4 wt%... more The aim of this work is to evaluate the machinability of Pb-free brasses with Si from 1% to 4 wt%, which were prepared using Cu 60/Zn 40 and Cu 80/Si 20 Pb-free master alloys. Machinability of the investigated alloys is tested based on cutting force, tool wear, surface roughness, and chip type. In the 1 wt% Si alloy, which exhibits maximum strength, the maximum cutting force is measured and undesirable continuous chip type is produced, while tool wear and machined surface roughness have the lowest values. Increasing the silicon content from 1% to 4%, results in increasing the tool wear by 140%, machined surface roughness by 25%, while the chip type changed from continuous to discontinuous type, and the cutting force was reduced by 50%. Machinability results are correlated with the alloy mechanical properties and with the phases present in the microstructure.

Research paper thumbnail of Cold Compaction of Al-Zn Powder Composite Materials

Key Engineering Materials, 1993

... Figure (3.b) shows that increasing compaction load raises the reltive density for all particl... more ... Figure (3.b) shows that increasing compaction load raises the reltive density for all particle sizes and that the finner ps corresponds to the higher relative density. Figure (4), supports the same result in a relationship between specimen height and compaction load. Page 4. ...

Research paper thumbnail of Prediction of Hypoeutectic Gray Iron Microstructure during Solidification and Solid Transformation Using Simple Fourier Model

Abstract Phases' evolution during the solidification of a hypoeutectic 3.92% C-equivalen... more Abstract Phases' evolution during the solidification of a hypoeutectic 3.92% C-equivalence cast iron was modelled by considering the cooling history of the alloy from the melt, thus including both solidification and solid state transformations. Simple Fourier model was ...

Research paper thumbnail of Solidification Simulation of Equiaxed Grains in Al - Si Eutectic Alloys

Materials Science Forum, 1996

Page 1. Materials Science Forum Vols. 217-222 (1996) pp 347-352 © (1996) Trans Tech Publications,... more Page 1. Materials Science Forum Vols. 217-222 (1996) pp 347-352 © (1996) Trans Tech Publications, Switzerland doi: 10.4028/www. scientific. net/MSF. 217-222.34 7 Solidification Simulation of Equiaxed Grains in Al - Si Eutectic ...

Research paper thumbnail of Relationship between formability and cast structures in end-chill directionally solidified Al–Cu alloys

Materials & Design, 2002

End-chill unidirectional solidification experiments have been conducted on pure Al and Al᎐Cu allo... more End-chill unidirectional solidification experiments have been conducted on pure Al and Al᎐Cu alloys with 1, 3 and 4.5 wt.% Cu, using melt superheat varying between 50 and 200 K. The specimens produced were 50 mm in diameter and 150᎐200 mm long. Studying the solidification structure indicated that most of the specimens exhibited a columnar structure growing perpendicular to the chill surface, followed by equiaxed grains. The volume fraction of the columnar structure and the grain size of the equiaxed one are related to the Cu content, superheat and the cooling rate. The volume fraction of the eutectic phase varied, depending on the casting parameters. Compression testing has been performed, in order to study the formability of the columnar and equiaxed Ž . grain structures. Constant testing conditions of a specimen slenderness ratio 8: 8 and strain rate of 1 mmrs were used, as well as a lubricant. In the relationship s k n , describing the true stressrtrue strain relationship for the region between the limits of Ž . Ž . initial yielding and necking in ductile materials, the strength coefficient k and strain hardening coefficient n are used as indices for formability. Hence, the difference in formability behaviour between the columnar and equiaxed grains is presented. ᮊ

Research paper thumbnail of Tungsten-Reinforced Niobium Intermetallic Composites: Fabrication and Interface Reaction

Key Engineering Materials, 1993

Research paper thumbnail of Structural response to shape variations in the AI-AI3Ni eutectic composite

Metallurgical Transactions A, 1979

Page 1. Structural Response to Shape Variations in the AI-AI3Ni Eutectic Composite NAHED A. EL-MA... more Page 1. Structural Response to Shape Variations in the AI-AI3Ni Eutectic Composite NAHED A. EL-MAHALLAWYAND MAHMOUD M. FARAG Structural irregularities that arise due to shape variations in A1-A13Ni directionally solidified eutectic composites have been analyzed. ...

Research paper thumbnail of Microstructure of In-Situ composites

Materialwissenschaft und Werkstofftechnik, 1983

ABSTRACT

Research paper thumbnail of Morphological variations in melt-spun AlCu alloys

Materials Science and Engineering: A, 1991

Research paper thumbnail of On the technological properties of steel strips aluminized in Al-Si baths

Journal of Materials Science Letters, 1996

... Mer. Finishing 80 (1980) 21. 4. H. LUDWIG, E. ULRICH and W. WILHELM, Prakt. Metallogr. 31 (19... more ... Mer. Finishing 80 (1980) 21. 4. H. LUDWIG, E. ULRICH and W. WILHELM, Prakt. Metallogr. 31 (1994) 78. 5. MA SHADY, AR EL-SISSI, MA ATTIA, NA EL-MAHALLAWY,MA TAHA and W. REIF, J. Mar. Sei. TechnoL, submitted. 6 ...

Research paper thumbnail of Simulations and experiments in pressurized solidification process (PSP) and rapid solidification process (RSP)

Journal of Materials Science Letters, 1985

The present work shows numerical models and experiments in two solidification processes: pressuri... more The present work shows numerical models and experiments in two solidification processes: pressurized solidification (PSP) and rapid solidification (RSP). In PSP, the application of pressure leads to higher cooling rates due to the minimization of air gap at the metal/mould interface. In RSP, the high cooling rates obtained are function of the process parameters like melt superheat, wheel material, temperature and velocity and the surrounding atmosphere.

Research paper thumbnail of Metal-mould heat transfer coefficient using end-chill experiments

Journal of Materials Science Letters, 1988

In several casting processes, directional solidification by the use of end-chill is used to produ... more In several casting processes, directional solidification by the use of end-chill is used to produce steep temperature gradients within the casting. Mathematical modelling or computer simulation of solidification has proved to be a powerful tool for process control and optimization of parameters in several areas . For the computer simulation to be accurate, several thermal data are needed. Besides the thermal properties of the materials in use, information about metal-mould heat transfer coefficients and convection in the melt are needed .

Research paper thumbnail of Effect of melt superheat on heat transfer coefficient for aluminium solidifying against copper chill

Journal of Materials Science, 1991

Solidification of metal castings inside moulds is mainly dependent on the heat flow from the meta... more Solidification of metal castings inside moulds is mainly dependent on the heat flow from the metal to the mould which is in turn proportional to an overall heat transfer coefficient h which includes all resistances to heat flow such as the presence of an air gap. In the present work the heat transfer coefficient is determined using a directional solidification set-up with end chill for solidifying commercial-purity aluminium with different superheats (40 K and 115 K) against copper chill. A computer program solving the heat conduction and convection in the solidifying metal is used together with the experimental temperature history in order to determine the heat transfer coefficient at the interface. The variation of h as a function of time, surface temperature and gap temperature for each melt superheat is found. The results indicate that h reaches a maximum value for surface temperature close to the liquidus. The analysis of heat flux from the metal to the mould indicates that it is mainly by conduction. The air gap size is evaluated with time, surface temperature and with melt superheat. It is found that higher h values and smaller gap sizes are obtained with higher superheats.

Research paper thumbnail of Effect of melt superheat and chill material on interfacial heat-transfer coefficient in end-chill Al and Al-Cu alloy castings

Journal of Materials Science, 1992

Solidification of metal castings inside moulds is mainly dependent on the rate of heat removal fr... more Solidification of metal castings inside moulds is mainly dependent on the rate of heat removal from the metal to the mould. During casting solidification, an air gap usually develops at the interface between the solidfying metal and the surrounding mould or chill. This condition occurs in most casting geometries, except in some cases such as the cast metal solidifying around a central core. An overall heat-transfer coefficient, which includes all resistances to heat flow from the metal to its surroundings can be determined. The objective of this work was to determine the overall heat-transfer coefficient,h, using experimental and computersimulation results on commercial purity aluminium and Al-4.5 wt% Cu alloy solidifying in a vertical end-chill apparatus. The cast ingots had a cylindrical shape with 12.5 mm diameter and different lengths of 95 and 230 mm. It solidified at different superheats (ranging from 50–110 °C) against two different chill materials: copper, and dry moulding sand. A computer program solving the heat-conduction equation and taking into consideration the convection in the melt, was used to compute the temperature history at numerous points along the ingot length. Differenth values were assumed as a function of time, until agreement between experimental and computed cooling curves was obtained. The variation ofh as a function of time, surface temperature, specimen length for each melt superheat and chill material was found. The thickness of the air gap was also evaluated. The results indicate that the variation of heat-transfer coefficient with time followed a pattern of sudden increase for the first few seconds, followed by a steady state, after whichh decreased and reached another lower constant value. Theh values were also found to decrease rapidly when the liquidus temperature was reached in the melt. For longer specimen and higher melt superheat, the heat-transfer coefficient increased. It was also higher for a copper than for a sand chill.

Research paper thumbnail of Control of the continuous rheocasting process

Journal of Materials Science, 1988

In the continuous rheocasting process, a semi-solid alloy is obtained from the exit port of the a... more In the continuous rheocasting process, a semi-solid alloy is obtained from the exit port of the apparatus at a given rate and with a given fraction of solid. This solid fraction is dependent on the corresponding temperature within the solid-liquid range which should be controlled accurately by the process parameters for a given rheocaster stirring chamber. For this purpose a heat flow model has been established for the continuous rheocasting of Bi-17 wt% Sn alloy. The heat transfer calculations are based on the solution of the two-dimensional partial differential equations using a finite difference method. An excellent agreement between calculations and experimental results is found. Computations are carried out in order to find the influence of stirring chamber dimensions on the alloy exit temperature and therefore, the volume fraction of solid. The influence of input metal temperature and metal flow rate on the exit temperature and volume fraction of solid are also found.

Research paper thumbnail of Surface roughness and mechanical properties of melt-spun Al-Cu ribbons

Journal of Materials Science, 1992

AI, and AI-33wt% Cu ribbons with different thicknesses, t, have been prepared by chilled block me... more AI, and AI-33wt% Cu ribbons with different thicknesses, t, have been prepared by chilled block melt spinning under different processing conditions. Surface roughness, taken as peak to valley values, Rt, measured on both the substrate and air sides of the ribbon, shows great dependence on substrate velocity, v, ejection gas pressure, P, nozzle height above the substrate, H, and a lesser dependence on substrate thermal conductivity, k, and melt superheat, AT. The bulk density over all the zones shows an increase over conventionally cast alloys of 7.4% for AI-33 wt% Cu and about 3% for aluminium. Microhardness, Hn, measurements inside each of the three microstructure zones, which were identified across the ribbon section, show variation with t as Hn = Ho t-m, where the constant H o depends on the microstructure zone and m depends on the alloy composition. The zone at the substrate side has the highest Ha values and that at the air side has the lowest ones. The number of bending cycles to fracture, which is taken as a measure of ductility, increased with ribbon thickness and decreased with copper content.

Research paper thumbnail of On crack susceptibility in the submerged arc welding of medium-carbon steel plates

Journal of Materials Processing Technology, 1997

Research paper thumbnail of Workability of unidirectionally solidified Al-8 wt% Cu alloy: Part I. Cold workability

Journal of Materials Processing Technology, 1992

The cold workability of unidirectionally solidified commercial A1-8 wt% Cu alloy is studied using... more The cold workability of unidirectionally solidified commercial A1-8 wt% Cu alloy is studied using the cold-upsetting test in the axial direction of the specimens. A constant temperature gradient and different growth rates were used to produce an arrayed dendritic morphology with different sizes. Different friction conditions and aspect ratios were used in the tests. The influence of the structure size and the upsetting conditions on the limiting strains, the limiting reduction in height and the forming-limit lines are presented. The cracks formed on the barreled surface of the specimens are examined.

Research paper thumbnail of Some experimental data on workability of aluminium-particulate-reinforced metal matrix composites

Journal of Materials Processing Technology, 2008

... composites. Mohamed A. Taha Corresponding Author Contact Information , a , E-mail The Corresp... more ... composites. Mohamed A. Taha Corresponding Author Contact Information , a , E-mail The Corresponding Author , Nahed A. El-Mahallawy a and Ahmed M. El-Sabbagh a. a Faculty of Engineering, Ain-Shams University, Cairo, Egypt. ...