ÐThe synthesis, microstructural characterization and microhardness of nanocrystalline B2-phase Ni... more ÐThe synthesis, microstructural characterization and microhardness of nanocrystalline B2-phase NiAl intermetallic are discussed in this paper. Nanophase NiAl powders were prepared by mechanical alloying of elemental Ni and Al powders under an argon atmosphere for dierent times (0±48 h). The alloyed nanocrystalline powders were then consolidated by shock compaction at a peak pressure of 4± 6 GPa, to 83% dense compacts. Characterization by transmission electron microscopy (TEM) revealed that the microstructure of the shock-consolidated sample was retained at the nanoscale. The average crystallite size measurements revealed that mechanically alloyed NiAl grain size decreased from 48 227 to 923 nm with increasing mechanical alloying time from 8 to 48 h. The long-range-order parameters of powders mechanically alloyed for dierent times were determined, and were observed to vary between 0.82 for 5 h and 0.63 for 48 h of milling time. Following shock compaction, the long-range-order parameter was determined to be 0.76, 0.69 and 0.66, respectively, for the 16, 24 and 48 h alloyed specimens. Both the mechanically alloyed nanocrystalline NiAl powder and the shock-consolidated bulk specimen showed evidence of grain boundary dislocations, subgrains, and distorted regions. A large number of grain boundaries and defects were observed via high resolution TEM (HRTEM). Shear bands were also observed in the mechanically alloyed NiAl intermetallic powders and in the shock-consolidated compacts. Microhardness measurements of shock-consolidated material showed increasing microhardness with increasing crystallite size re®nement, following Hall±Petch behavior.
An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media m... more An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media material for grinding iron ore in a ball mill. Spheroidal graphite (S.G) iron balls are austenitised at 900° C for 60 minutes and given stepped austempering treatment at 280° C for 30 minutes and 60 minutes followed by 380° C for 60 minutes in
The work focuses on mechanical alloying of elemental powders, high energy rate ball milling is ut... more The work focuses on mechanical alloying of elemental powders, high energy rate ball milling is utilised to achieve mechanical alloying of Fe and Al. Mechanical alloying in a toluene media and its effects on atmospheric and milling media contaminations are looked into. Phase transformation, structural properties, composition and particle size during mechanical alloying are investigated by X ray diffraction (XRD), energy dispersive spectroscopy (EDS) and transmission electron microscope (TEM). Scanning electron microscope SEM) is utilised to study the morphology of unmilled and as milled powder particles. Elevated temperature behaviour during the processing is investigated by differential scanning calorimeter (DSC). Room temperature magnetic and thermo magnetic properties were investigated by vibrating sample magnetometer. Transition to an ordered structure from disorder and nanostructure are proved by XRD and TEM, alloying of elemental phases, ordering, recrystallisation and grain gr...
Objective of the work was to synthesize nanostructured FeAl alloy powder by mechanical alloying (... more Objective of the work was to synthesize nanostructured FeAl alloy powder by mechanical alloying (MEA). The work concentrated on synthesis, characterization, structural and mechanical properties of the alloy. Nanostructured FeAl intermetallics were prepared directly by MEA in a high energy rate ball mill. Milling was performed under toluene solution to avoid contamination from the milling media and atmosphere. Mixtures of elemental Fe and Al were progressively transformed into a partially disordered solid solution with an average composition of Fe—50 at % Al. Phase transformation, structural changes, morphology, particle size measurement and chemical composition during MEA were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS) respectively. Vickers micro hardness (VMH) indentation tests were performed on the powders. XRD and SEM studies revealed the alloying of elemental powders as well as transition to nanostru...
An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media m... more An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media material for grinding iron ore in a ball mill. Spheroidal graphite (S.G) iron balls are austenitised at 900° C for 60 minutes and given stepped austempering treatment at 280° C for 30 minutes and 60 minutes followed by 380° C for 60 minutes in
Mechanically alloyed powders synthesized by high energy rate ball milling were consolidated to pr... more Mechanically alloyed powders synthesized by high energy rate ball milling were consolidated to produce bulk polycrystalline Al-50 at. % Fe alloy. Consolidation was achieved by cold compaction and sintering, while annealing was done to obtain an ordered structure. Annealed samples were deformed plastically by a range of compression stresses. Combination of characterization techniques like x-ray diffraction, transmission electron microscopy, vibrating sample magnetometry and Vicker’s micro hardness measurement were utilized to examine different properties. Annealed sample exhibited ordered and non magnetic phase while deformation induced samples showed simultaneous transition to both disorder and ferromagnetism, the transitional alloy at intermediate state possessed partial disorder and low magnetization. The long range order and lattice expansion contribute to the increase in magnetism at low compression stresses while it is only due to the lattice expansion at higher stresses. The order to disorder transition can be assessed by micro hardness measurement.
International Symposium on Quality Electronic Design, 2013
Wireless Network-on-Chip (WiNoC) has emerged as an enabling technology to design low power and hi... more Wireless Network-on-Chip (WiNoC) has emerged as an enabling technology to design low power and high bandwidth massive multi-core chips. The performance advantages mainly stem from using the wireless links as long-range shortcuts between far apart cores. This performance gain can be enhanced further if the characteristics of the wireline links and the processing cores of the WiNoC are optimized according to the traffic patterns and workloads. In this work, we demonstrate that by incorporating both processor-and network-level dynamic voltage and frequency scaling (DVFS) in a WiNoC, the power and thermal profiles can be enhanced without a significant impact on the overall execution time. We also show that depending on the benchmark applications, temperature hotspots can be formed either in the processing core or in the network infrastructure. The proposed duallevel DVFS is capable of addressing both.
Elemental powders of Fe and Al were mechanically alloyed using a high energy rate ball mill. A na... more Elemental powders of Fe and Al were mechanically alloyed using a high energy rate ball mill. A nanostructure disordered Fe(Al) solid solution was formed at an early stage. After 28 h of milling, it was found that the Fe(Al) solid solution was transformed into an ordered FeAl phase. During the entire ball milling process, the elemental phase co-existed with the alloyed phase. Ball milling was performed under toluene to minimise atmospheric contamination. Ball milled powders were subsequently annealed to induce more ordering. Phase transformation and structural changes during mechanical alloying (MEA) and subsequent annealing were investigated by X-ray diffraction (XRD). Scanning electron microscope (SEM) was employed to examine the morphology of the powders and to measure the powder particle size. Energy dispersive spectroscopy (EDS) was utilised to examine the composition of mechanically alloyed powder particles. XRD and EDS were also employed to examine the atmospheric and milling media contamination. Phase transformation at elevated temperatures was examined by differential scanning calorimeter (DSC). The crystallite size obtained after 28 h of milling time was around 18 nm. Ordering was characterised by small reduction in crystallite size while large reduction was observed during disordering. Micro hardness was influenced by Crystallite size and structural transformation.
Mechanically alloyed powders were consolidated to produce bulk polycrystalline Fe-50 at.%Al alloy... more Mechanically alloyed powders were consolidated to produce bulk polycrystalline Fe-50 at.%Al alloy. Consolidation was achieved by cold compaction and sintering. Annealing was applied to the consolidated samples to obtain an ordered structure. Annealed samples were further deformed plastically by a range of compression stresses. Combination of characterization techniques including X-ray diffraction, transmission electron microscope, vibrating sample magnetometer and Vicker’s micro hardness were used to examine different properties. Results indicated that annealed sample exhibits ordered and non-magnetic phase while deformation induces simultaneously a transition to both disorder and ferromagnetism. The transitional alloy at intermediate state possesses partial disorder and low magnetization. Ferromagnetism is governed by anti site in the ordered matrix, in fact, the long range order and lattice expansion contribute to the increase in magnetism at low compression stresses while it is o...
ÐThe synthesis, microstructural characterization and microhardness of nanocrystalline B2-phase Ni... more ÐThe synthesis, microstructural characterization and microhardness of nanocrystalline B2-phase NiAl intermetallic are discussed in this paper. Nanophase NiAl powders were prepared by mechanical alloying of elemental Ni and Al powders under an argon atmosphere for dierent times (0±48 h). The alloyed nanocrystalline powders were then consolidated by shock compaction at a peak pressure of 4± 6 GPa, to 83% dense compacts. Characterization by transmission electron microscopy (TEM) revealed that the microstructure of the shock-consolidated sample was retained at the nanoscale. The average crystallite size measurements revealed that mechanically alloyed NiAl grain size decreased from 48 227 to 923 nm with increasing mechanical alloying time from 8 to 48 h. The long-range-order parameters of powders mechanically alloyed for dierent times were determined, and were observed to vary between 0.82 for 5 h and 0.63 for 48 h of milling time. Following shock compaction, the long-range-order parameter was determined to be 0.76, 0.69 and 0.66, respectively, for the 16, 24 and 48 h alloyed specimens. Both the mechanically alloyed nanocrystalline NiAl powder and the shock-consolidated bulk specimen showed evidence of grain boundary dislocations, subgrains, and distorted regions. A large number of grain boundaries and defects were observed via high resolution TEM (HRTEM). Shear bands were also observed in the mechanically alloyed NiAl intermetallic powders and in the shock-consolidated compacts. Microhardness measurements of shock-consolidated material showed increasing microhardness with increasing crystallite size re®nement, following Hall±Petch behavior.
An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media m... more An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media material for grinding iron ore in a ball mill. Spheroidal graphite (S.G) iron balls are austenitised at 900° C for 60 minutes and given stepped austempering treatment at 280° C for 30 minutes and 60 minutes followed by 380° C for 60 minutes in
The work focuses on mechanical alloying of elemental powders, high energy rate ball milling is ut... more The work focuses on mechanical alloying of elemental powders, high energy rate ball milling is utilised to achieve mechanical alloying of Fe and Al. Mechanical alloying in a toluene media and its effects on atmospheric and milling media contaminations are looked into. Phase transformation, structural properties, composition and particle size during mechanical alloying are investigated by X ray diffraction (XRD), energy dispersive spectroscopy (EDS) and transmission electron microscope (TEM). Scanning electron microscope SEM) is utilised to study the morphology of unmilled and as milled powder particles. Elevated temperature behaviour during the processing is investigated by differential scanning calorimeter (DSC). Room temperature magnetic and thermo magnetic properties were investigated by vibrating sample magnetometer. Transition to an ordered structure from disorder and nanostructure are proved by XRD and TEM, alloying of elemental phases, ordering, recrystallisation and grain gr...
Objective of the work was to synthesize nanostructured FeAl alloy powder by mechanical alloying (... more Objective of the work was to synthesize nanostructured FeAl alloy powder by mechanical alloying (MEA). The work concentrated on synthesis, characterization, structural and mechanical properties of the alloy. Nanostructured FeAl intermetallics were prepared directly by MEA in a high energy rate ball mill. Milling was performed under toluene solution to avoid contamination from the milling media and atmosphere. Mixtures of elemental Fe and Al were progressively transformed into a partially disordered solid solution with an average composition of Fe—50 at % Al. Phase transformation, structural changes, morphology, particle size measurement and chemical composition during MEA were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS) respectively. Vickers micro hardness (VMH) indentation tests were performed on the powders. XRD and SEM studies revealed the alloying of elemental powders as well as transition to nanostru...
An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media m... more An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media material for grinding iron ore in a ball mill. Spheroidal graphite (S.G) iron balls are austenitised at 900° C for 60 minutes and given stepped austempering treatment at 280° C for 30 minutes and 60 minutes followed by 380° C for 60 minutes in
Mechanically alloyed powders synthesized by high energy rate ball milling were consolidated to pr... more Mechanically alloyed powders synthesized by high energy rate ball milling were consolidated to produce bulk polycrystalline Al-50 at. % Fe alloy. Consolidation was achieved by cold compaction and sintering, while annealing was done to obtain an ordered structure. Annealed samples were deformed plastically by a range of compression stresses. Combination of characterization techniques like x-ray diffraction, transmission electron microscopy, vibrating sample magnetometry and Vicker’s micro hardness measurement were utilized to examine different properties. Annealed sample exhibited ordered and non magnetic phase while deformation induced samples showed simultaneous transition to both disorder and ferromagnetism, the transitional alloy at intermediate state possessed partial disorder and low magnetization. The long range order and lattice expansion contribute to the increase in magnetism at low compression stresses while it is only due to the lattice expansion at higher stresses. The order to disorder transition can be assessed by micro hardness measurement.
International Symposium on Quality Electronic Design, 2013
Wireless Network-on-Chip (WiNoC) has emerged as an enabling technology to design low power and hi... more Wireless Network-on-Chip (WiNoC) has emerged as an enabling technology to design low power and high bandwidth massive multi-core chips. The performance advantages mainly stem from using the wireless links as long-range shortcuts between far apart cores. This performance gain can be enhanced further if the characteristics of the wireline links and the processing cores of the WiNoC are optimized according to the traffic patterns and workloads. In this work, we demonstrate that by incorporating both processor-and network-level dynamic voltage and frequency scaling (DVFS) in a WiNoC, the power and thermal profiles can be enhanced without a significant impact on the overall execution time. We also show that depending on the benchmark applications, temperature hotspots can be formed either in the processing core or in the network infrastructure. The proposed duallevel DVFS is capable of addressing both.
Elemental powders of Fe and Al were mechanically alloyed using a high energy rate ball mill. A na... more Elemental powders of Fe and Al were mechanically alloyed using a high energy rate ball mill. A nanostructure disordered Fe(Al) solid solution was formed at an early stage. After 28 h of milling, it was found that the Fe(Al) solid solution was transformed into an ordered FeAl phase. During the entire ball milling process, the elemental phase co-existed with the alloyed phase. Ball milling was performed under toluene to minimise atmospheric contamination. Ball milled powders were subsequently annealed to induce more ordering. Phase transformation and structural changes during mechanical alloying (MEA) and subsequent annealing were investigated by X-ray diffraction (XRD). Scanning electron microscope (SEM) was employed to examine the morphology of the powders and to measure the powder particle size. Energy dispersive spectroscopy (EDS) was utilised to examine the composition of mechanically alloyed powder particles. XRD and EDS were also employed to examine the atmospheric and milling media contamination. Phase transformation at elevated temperatures was examined by differential scanning calorimeter (DSC). The crystallite size obtained after 28 h of milling time was around 18 nm. Ordering was characterised by small reduction in crystallite size while large reduction was observed during disordering. Micro hardness was influenced by Crystallite size and structural transformation.
Mechanically alloyed powders were consolidated to produce bulk polycrystalline Fe-50 at.%Al alloy... more Mechanically alloyed powders were consolidated to produce bulk polycrystalline Fe-50 at.%Al alloy. Consolidation was achieved by cold compaction and sintering. Annealing was applied to the consolidated samples to obtain an ordered structure. Annealed samples were further deformed plastically by a range of compression stresses. Combination of characterization techniques including X-ray diffraction, transmission electron microscope, vibrating sample magnetometer and Vicker’s micro hardness were used to examine different properties. Results indicated that annealed sample exhibits ordered and non-magnetic phase while deformation induces simultaneously a transition to both disorder and ferromagnetism. The transitional alloy at intermediate state possesses partial disorder and low magnetization. Ferromagnetism is governed by anti site in the ordered matrix, in fact, the long range order and lattice expansion contribute to the increase in magnetism at low compression stresses while it is o...
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