Viet Nguyen-Hoang | Hanoi University of Science and Technology (original) (raw)

Papers by Viet Nguyen-Hoang

Research paper thumbnail of Formation of Metastable Phases of the Ni-Al System by Mechanical Milling

... Crystalline size of nanoparticles can be calculated by Hall-William formula: ... The average ... more ... Crystalline size of nanoparticles can be calculated by Hall-William formula: ... The average grain size of the sample after 40 h milling calculated from the Hall-William formula based on the XRD pattern and from the SEM images was about 25 nm. ...

Research paper thumbnail of Structure evolution of a magnetite iron ore/carbon composite pellet during solid-state reduction under microwave heating

Journal of Science and Technology of Metal, 2021

In the present study, the structure evolution under direct reduction of a Minh-Son magnetite iron... more In the present study, the structure evolution under direct reduction of a Minh-Son magnetite iron ore/carbon composite pellets in a microwave-heating kiln under different microwave wattage of 60 and 90 % (with the firing time from 15 to 120 min.) was investigated. The microstructure of the pellets was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction (XRD). The phase formation was indexed using MDI Jade from the peaks matching the reference sample. At the microwave’s wattage of 60 %: the wustite (FeO) has appeared after firing time of 60 min., the metallic iron and fayalite have appeared in the reduced samples after firing time of 90 min. to 120 min. with retained phases of Fe203, Fe304, FeO and Si02– While at the microwave’s wattage of 90 %, the metallic iron has appeared in the reduced samples after firing time of 30 min. to 120 min and fayalite has appeared in the reduced samples after firing time of 60 min. to 120 min...

Research paper thumbnail of Effect of Process-Control Agents on Characteristics of Amorphous Al-Y-Ni-Co Alloy Powder Produced by Mechanical Alloying

Journal of Korean Powder Metallurgy Institute, 2010

Research paper thumbnail of The Formation and Crystallization of Amorphous Ti50Cu50Ni20Al10Powder Prepared by High-Energy Ball Milling

Journal of Korean Powder Metallurgy Institute, 2009

Research paper thumbnail of Mechanical Properties of Bulk Amorphous Ti50Cu20Ni20Al10Fabricated by High-energy Ball Milling and Spark-plasma Sintering

Journal of Korean Powder Metallurgy Institute, 2009

Research paper thumbnail of Fabrication of Fe-TiC Composite by High-Energy Milling and Spark-Plasma Sintering

Journal of Korean Powder Metallurgy Institute, 2013

Fe-TiC composite was fabricated from Fe and TiC powders by high-energy milling and subsequent spa... more Fe-TiC composite was fabricated from Fe and TiC powders by high-energy milling and subsequent sparkplasma sintering. The microstructure, particle size and phase of Fe-TiC composite powders were investigated by field emission scanning electron microscopy and X-ray diffraction to evaluate the effect of milling conditions on the size and distribution of TiC particles in Fe matrix. TiC particle size decreased with milling time. The average TiC particle size of 38 nm was obtained after 60 minutes of milling at 1000 rpm. Prepared Fe-TiC powder mixture was densified by sparkplasma sintering. Sintered Fe-TiC compacts showed a relative density of 91.7~96.2%. The average TiC particle size of 150 nm was observed from the FE-SEM image. The microstructure, densification behavior, Vickers hardness, and fracture toughness of Fe-TiC sintered compact were investigated.

Research paper thumbnail of Crystallization Kinetics of Al-Fe and Al-Fe-Y Amorphous Alloys Produced by Mechanical Milling

Journal of Nanomaterials, 2016

In this work, the effect of a slight change in the composition of the Al-Fe amorphous alloys (fro... more In this work, the effect of a slight change in the composition of the Al-Fe amorphous alloys (from Al84Fe16to Al82Fe18) and the substitution of Y for Al (2 at.%) on their crystallization kinetics was studied. According to the X-ray diffraction analysis, powders of the Al84Fe16, Al82Fe18, and Al82Fe16Y2alloys with a fully amorphous structure were formed after 100 h of mechanical milling of the mixtures of the elemental powders. The crystallization behavior of the alloys was also studied by transmission electron microscopy. Upon heating up to a temperature of the first exothermic peak,α-Al crystals precipitated from the amorphous Al84Fe16matrix. During crystallization of the Al82Fe18alloy, crystals of the Al6Fe intermetallic compound formed along withα-Al crystals. Substitution of Y for 2 at.% of Al in the Al82Fe16Y2alloy made crystallization of the alloy more complicated:α-Al, Al6Fe, and Fe4Y crystals coexisted with an amorphous phase. The activation energies corresponding to the fir...

Research paper thumbnail of Structural Investigations of TiC–Cu Nanocomposites Prepared by Ball Milling and Spark Plasma Sintering

Metals, 2017

In this work, TiC-Cu composites containing 20 and 30 vol % of nano-sized titanium carbide (TiC) p... more In this work, TiC-Cu composites containing 20 and 30 vol % of nano-sized titanium carbide (TiC) particles were prepared by powder metallurgy using copper powders with micrometer-sized and nanometer-sized particles. Mixtures of TiC and Cu powders were ball milled for 10 h and spark plasma sintered at 800-900 • C under an applied pressure of 50 MPa. The relative density of the sintered composites was 95.0%-96.5%. The composites fractured in a ductile mode. The crystallite size of the copper matrix in the composites prepared using the nanometer-sized copper powder was smaller than that in composites prepared using the micrometer-sized copper powder, which was confirmed by transmission electron microscopy (TEM). The hardness of the composites increased as the sintering temperature was increased from 800 to 900 • C. When the TiC content increased from 20 to 30 vol %, the hardness of the composites obtained from the micrometer-sized copper powder and sintered at 900 • C increased from 284 to 315 HV, while in composites obtained from the nanometer-sized copper, the hardness decreased from 347 to 337 HV.

Research paper thumbnail of Characterization of In-Situ Cu–TiH2–C and Cu–Ti–C Nanocomposites Produced by Mechanical Milling and Spark Plasma Sintering

Metals, 2017

This study focuses on the fabrication and microstructural investigation of Cu-TiH2-C and Cu-TiC n... more This study focuses on the fabrication and microstructural investigation of Cu-TiH2-C and Cu-TiC nanocomposites with different volume fractions (10% and 20%) of TiC. Two mixtures of powders were ball milled for 10 h, consequently consolidated by spark plasma sintering (SPS) at 900 and 1000 • C producing bulk materials with relative densities of 95-97%. The evolution process of TiC formation during sintering process was studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM). XRD patterns of composites present only Cu and TiC phases, no residual Ti phase can be detected. TEM images of composites with (10 vol % TiC) sintered at 900 • C show TiC nanoparticles about 10-30 nm precipitated in copper matrix, most of Ti and C dissolved in the composite matrix. At the higher sintering temperature of 1000 • C, more TiC precipitates from Cu-TiH2-C than those of Cu-TiC composite, particle size ranges from 10 to 20 nm. The hardness of both nanocomposites also increased with increasing sintering temperature. The highest hardness values of Cu-TiH2-C and Cu-TiC nanocomposites sintered at 1000 • C are 314 and 306 HV, respectively.

Research paper thumbnail of 고에너지 밀링 및 합성반응에 의한 Fe-TiC 복합분말 제조

Journal of Korean Powder Metallurgy Institute, 2013

TiB 2-reinforced iron matrix composite (Fe-TiB 2) powder was in-situ fabricated from titanium hyd... more TiB 2-reinforced iron matrix composite (Fe-TiB 2) powder was in-situ fabricated from titanium hydride (TiH 2) and iron boride (FeB) powders by the mechanical activation and a subsequent reaction. Phase formation of the composite powder was identified by X-ray diffraction (XRD). The morphology and phase composition were observed and measured by field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The results showed that TiB 2 particles formed in nanoscale were uniformly distributed in Fe matrix. Fe 2 B phase existed due to an incomplete reaction of Ti and FeB. Effect of milling process and synthesis temperature on the formation of composite were discussed.

Research paper thumbnail of Consolidation and Mechanical Properties of Mechanically Alloyed Al-Mg Powders

MRS Proceedings, 2008

Nanostructured Al-Mg bulk samples with compositions in the range of 10 – 40 at.% Mg have been pro... more Nanostructured Al-Mg bulk samples with compositions in the range of 10 – 40 at.% Mg have been produced by consolidation of mechanical alloyed powders. Powders with composition Al90Mg10 and Al80Mg20 were consolidated into highly dense specimens by hot extrusion. Room temperature compression tests for the Al90Mg10 specimen reveal interesting mechanical properties, namely, a high strength of 630 MPa combined with a plastic strain of about 4 %. The increase of the Mg content to 20 at.% increases the strength by about 100 MPa but it suppresses plastic deformation. The Al60Mg40 powder was consolidated at different temperatures by spark plasma sintering and the effect of the sintering temperature on microstructure, density and hardness have been studied. The results reveal that both density and hardness of the consolidated samples increase with increasing sintering temperature, while retaining a nanocrystalline structure. These results indicate that powder metallurgy is a suitable processi...

Research paper thumbnail of Thermal Stability of Amorphous Al-Fe-Y Prepared by Mechanical Alloying

Materials Science Forum, 2014

Al-Fe-Y amorphous alloys of Al84Fe16, Al82Fe18 and Al82Fe16Y2 composition were prepared by mechan... more Al-Fe-Y amorphous alloys of Al84Fe16, Al82Fe18 and Al82Fe16Y2 composition were prepared by mechanical alloying in a planetary ball mill P100. A nearly complete amorphization could be achieved for the Al84Fe16, Al82Fe18 and Al82Fe16Y2 powder alloys after 100h of milling at a rotational speed of 350 rpm in hexane medium. Differential scanning calorimetry (DSC) analyses revealed three-stage crystallization processes for Al82Fe18 and Al82Fe16Y2 alloys and four-stage crystallization processes for Al84Fe16 alloy, respectively. Taking into account the DSC data, the thermal stability increased in the order of Al84Fe16, Al82Fe18, and Al82Fe16Y2 composition. The Al82Fe16Y2 alloy exhibited a relatively better thermal stability than the other two alloys.

Research paper thumbnail of Synthesis and Characterization of Cu–TiC Nanocomposites by Ball Milling and Spark Plasma Sintering

Materials Science Forum, 2014

In this study, Cu-TiC nanocomposites were fabricated from a mixture of Cu and 5÷15% wt. TiC powde... more In this study, Cu-TiC nanocomposites were fabricated from a mixture of Cu and 5÷15% wt. TiC powders by ball milling and subsequent spark-plasma sintering. The morphology of Cu-TiC nanocomposite powders were observed by field emission scanning electron microscopy. Only characteristic peaks of Cu and TiC phases were detected from X-ray diffraction patterns of milled powder mixture. Sintered compacts showed a highly densified compacts (∼95% relative density) while retaining fine grains in the matrix. The hardness, wear resistance, and fracture surface of the sintered specimens were also investigated.

Research paper thumbnail of High-strength Al87Ni8La5 bulk alloy produced by spark plasma sintering of gas atomized powders

Journal of Materials Research, 2009

In situ devitrification and consolidation of gas atomized Al87Ni8La5 glassy powders into highly d... more In situ devitrification and consolidation of gas atomized Al87Ni8La5 glassy powders into highly dense bulk specimens was carried out by spark plasma sintering. Room temperature compression tests of the consolidated bulk material reveal remarkable mechanical properties, namely, high compression strength of 930 MPa combined with plastic strain exceeding 25%. These findings demonstrate that the combined devitrification and consolidation of glassy precursors by spark plasma sintering is a suitable method for the production of Al-based materials characterized by high strength and considerable plastic deformation.

Research paper thumbnail of Amorphous Ti–Cu–Ni–Al alloys prepared by mechanical alloying

Journal of Materials Science, 2009

Ti x (CuNi)90–x Al10 (x = 50, 55, 60) amorphous powder alloys were synthesized by mechanical allo... more Ti x (CuNi)90–x Al10 (x = 50, 55, 60) amorphous powder alloys were synthesized by mechanical alloying technique. The evolution of amorphization during milling and subsequent heat treatment was investigated by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The fully amorphous powders were obtained in the Ti50Cu20Ni20Al10, Ti55Cu17.5Ni17.5Al10 and Ti60Cu15Ni15Al10 alloys after milling for 30, 20 and 15 h, respectively. Differential scanning calorimetry revealed that thermal stability increased with the increasing (CuNi) content: Ti60Cu15Ni15Al10, Ti55Cu17.5Ni17.5Al10 and Ti50Cu20Ni20Al10. Heating of the three amorphous alloys at 800 K for 10 min results in the formation of the NiTi, NiTi2 and CuTi2 intermetallic phases.

Research paper thumbnail of Spark plasma sintering of gas atomized Al 87 Ni 8 La 5 amorphous powder

Journal of Physics: Conference Series, 2009

Bulk samples were prepared by in-situ devitrification and consolidation of gas atomized Al 87 Ni ... more Bulk samples were prepared by in-situ devitrification and consolidation of gas atomized Al 87 Ni 8 La 5 amorphous powder. Consolidation was carried out at different temperatures by spark plasma sintering, which leads to highly dense bulk specimens with a microstructure consisting of fcc aluminum together with Al 11 La 3 and Al 3 Ni intermetallic compounds. The consolidated powder displays a remarkably high compression stress, which depends on the sintering temperature and ranges between 900 and 1000 MPa, combined with plastic strain varying between 10 and 20 %. These results indicate that the mechanical properties of the samples can be tuned within a wide range of strength and ductility as a function of the sintering temperature used.

Research paper thumbnail of Structural characterization and magnetic properties of Al 82 Fe 16 TM 2 (TM: Ti, Ni, Cu) alloys prepared by mechanical alloying

A B S T R A C T In this work, the structural evolution of Al–16 at.%Fe–2 at.%TM (Transition Metal... more A B S T R A C T In this work, the structural evolution of Al–16 at.%Fe–2 at.%TM (Transition Metals (TM): Ti, Ni, Cu) alloys during mechanical alloying and their magnetic properties were investigated. The evolution of the phase composition and microstructure of the alloys with the milling time was studied using X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The phase composition of the alloys was determined using the Rietveld refinement of the XRD profiles. It was shown that the interaction between the components of the powder mixtures during milling started with dissolution of Fe in the Al crystalline lattice and Al in the Fe crystalline lattice. Upon further milling, ferromagnetic AlFe 3 (DO3) formed and further transformed into paramagnetic bcc-AlFe and later into an amorphous phase. It was found that the TM alloying elements significantly influence the kinetics of the transformations during milling: the Al 82 Fe 16 Ti 2 alloy was fully amorphous after 40 h of milling, the Al 82 Fe 16 Ni 2 alloy required 50 h of milling to achieve complete amorphization, and the Al 82 Fe 16 Cu 2 alloy was only partially amorphous after 60 h of milling. The interpretation of the observed alloying effect has been proposed. The magnetic properties of the alloys were correlated with the results of the structural characterization.

Research paper thumbnail of Structural Investigations of TiC–Cu Nanocomposites Prepared by Ball Milling and Spark Plasma Sintering

In this work, TiC–Cu composites containing 20 and 30 vol % of nano-sized titanium carbide (TiC) p... more In this work, TiC–Cu composites containing 20 and 30 vol % of nano-sized titanium carbide (TiC) particles were prepared by powder metallurgy using copper powders with micrometer-sized and nanometer-sized particles. Mixtures of TiC and Cu powders were ball milled for 10 h and spark plasma sintered at 800–900 • C under an applied pressure of 50 MPa. The relative density of the sintered composites was 95.0%–96.5%. The composites fractured in a ductile mode. The crystallite size of the copper matrix in the composites prepared using the nanometer-sized copper powder was smaller than that in composites prepared using the micrometer-sized copper powder, which was confirmed by transmission electron microscopy (TEM). The hardness of the composites increased as the sintering temperature was increased from 800 to 900 • C. When the TiC content increased from 20 to 30 vol %, the hardness of the composites obtained from the micrometer-sized copper powder and sintered at 900 • C increased from 284 to 315 HV, while in composites obtained from the nanometer-sized copper, the hardness decreased from 347 to 337 HV.

Research paper thumbnail of Characterization of In-Situ Cu–TiH2–C and Cu–Ti–C Nanocomposites Produced by Mechanical Milling and Spark Plasma Sintering

This study focuses on the fabrication and microstructural investigation of Cu–TiH2–C and Cu–Ti–C ... more This study focuses on the fabrication and microstructural investigation of Cu–TiH2–C and Cu–Ti–C nanocomposites with different volume fractions (10% and 20%) of TiC. Two mixtures of powders were ball milled for 10 h, consequently consolidated by spark plasma sintering (SPS) at 900 and 1000 • C producing bulk materials with relative densities of 95–97%. The evolution process of TiC formation during sintering process was studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM). XRD patterns of composites present only Cu and TiC phases, no residual Ti phase can be detected. TEM images of composites with (10 vol % TiC) sintered at 900 • C show TiC nanoparticles about 10–30 nm precipitated in copper matrix, most of Ti and C dissolved in the composite matrix. At the higher sintering temperature of 1000 • C, more TiC precipitates from Cu–TiH2–C than those of Cu–Ti–C composite, particle size ranges from 10 to 20 nm. The hardness of both nanocomposites also increased with increasing sintering temperature. The highest hardness values of Cu–TiH2–C and Cu–Ti–C nanocomposites sintered at 1000 • C are 314 and 306 HV, respectively.

Research paper thumbnail of Crystallization Kinetics of Al-Fe and Al-Fe-Y Amorphous Alloys Produced by Mechanical Milling

In this work, the effect of a slight change in the composition of the Al-Fe amorphous alloys (fro... more In this work, the effect of a slight change in the composition of the Al-Fe amorphous alloys (from Al 84 Fe 16 to Al 82 Fe 18) and the substitution of Y for Al (2 at.%) on their crystallization kinetics was studied. According to the X-ray diffraction analysis, powders of the Al 84 Fe 16 , Al 82 Fe 18 , and Al 82 Fe 16 Y 2 alloys with a fully amorphous structure were formed after 100 h of mechanical milling of the mixtures of the elemental powders. The crystallization behavior of the alloys was also studied by transmission electron microscopy. Upon heating up to a temperature of the first exothermic peak, í µí»¼-Al crystals precipitated from the amorphous Al 84 Fe 16 matrix. During crystallization of the Al 82 Fe 18 alloy, crystals of the Al 6 Fe intermetallic compound formed along with í µí»¼-Al crystals. Substitution of Y for 2 at.% of Al in the Al 82 Fe 16 Y 2 alloy made crystallization of the alloy more complicated: í µí»¼-Al, Al 6 Fe, and Fe 4 Y crystals coexisted with an amorphous phase. The activation energies corresponding to the first crystallization event of the alloys were calculated using the Kissinger and Ozawa methods. The values obtained by these two methods were in good agreement with each other and the same trends of changing with the alloy composition were observed. The Avrami exponent í µí±› was determined from the Johnson-Mehl-Avrami equation and showed that crystallization at the first stage is interface-controlled growth for all the three powder alloys studied.

Research paper thumbnail of Formation of Metastable Phases of the Ni-Al System by Mechanical Milling

... Crystalline size of nanoparticles can be calculated by Hall-William formula: ... The average ... more ... Crystalline size of nanoparticles can be calculated by Hall-William formula: ... The average grain size of the sample after 40 h milling calculated from the Hall-William formula based on the XRD pattern and from the SEM images was about 25 nm. ...

Research paper thumbnail of Structure evolution of a magnetite iron ore/carbon composite pellet during solid-state reduction under microwave heating

Journal of Science and Technology of Metal, 2021

In the present study, the structure evolution under direct reduction of a Minh-Son magnetite iron... more In the present study, the structure evolution under direct reduction of a Minh-Son magnetite iron ore/carbon composite pellets in a microwave-heating kiln under different microwave wattage of 60 and 90 % (with the firing time from 15 to 120 min.) was investigated. The microstructure of the pellets was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction (XRD). The phase formation was indexed using MDI Jade from the peaks matching the reference sample. At the microwave’s wattage of 60 %: the wustite (FeO) has appeared after firing time of 60 min., the metallic iron and fayalite have appeared in the reduced samples after firing time of 90 min. to 120 min. with retained phases of Fe203, Fe304, FeO and Si02– While at the microwave’s wattage of 90 %, the metallic iron has appeared in the reduced samples after firing time of 30 min. to 120 min and fayalite has appeared in the reduced samples after firing time of 60 min. to 120 min...

Research paper thumbnail of Effect of Process-Control Agents on Characteristics of Amorphous Al-Y-Ni-Co Alloy Powder Produced by Mechanical Alloying

Journal of Korean Powder Metallurgy Institute, 2010

Research paper thumbnail of The Formation and Crystallization of Amorphous Ti50Cu50Ni20Al10Powder Prepared by High-Energy Ball Milling

Journal of Korean Powder Metallurgy Institute, 2009

Research paper thumbnail of Mechanical Properties of Bulk Amorphous Ti50Cu20Ni20Al10Fabricated by High-energy Ball Milling and Spark-plasma Sintering

Journal of Korean Powder Metallurgy Institute, 2009

Research paper thumbnail of Fabrication of Fe-TiC Composite by High-Energy Milling and Spark-Plasma Sintering

Journal of Korean Powder Metallurgy Institute, 2013

Fe-TiC composite was fabricated from Fe and TiC powders by high-energy milling and subsequent spa... more Fe-TiC composite was fabricated from Fe and TiC powders by high-energy milling and subsequent sparkplasma sintering. The microstructure, particle size and phase of Fe-TiC composite powders were investigated by field emission scanning electron microscopy and X-ray diffraction to evaluate the effect of milling conditions on the size and distribution of TiC particles in Fe matrix. TiC particle size decreased with milling time. The average TiC particle size of 38 nm was obtained after 60 minutes of milling at 1000 rpm. Prepared Fe-TiC powder mixture was densified by sparkplasma sintering. Sintered Fe-TiC compacts showed a relative density of 91.7~96.2%. The average TiC particle size of 150 nm was observed from the FE-SEM image. The microstructure, densification behavior, Vickers hardness, and fracture toughness of Fe-TiC sintered compact were investigated.

Research paper thumbnail of Crystallization Kinetics of Al-Fe and Al-Fe-Y Amorphous Alloys Produced by Mechanical Milling

Journal of Nanomaterials, 2016

In this work, the effect of a slight change in the composition of the Al-Fe amorphous alloys (fro... more In this work, the effect of a slight change in the composition of the Al-Fe amorphous alloys (from Al84Fe16to Al82Fe18) and the substitution of Y for Al (2 at.%) on their crystallization kinetics was studied. According to the X-ray diffraction analysis, powders of the Al84Fe16, Al82Fe18, and Al82Fe16Y2alloys with a fully amorphous structure were formed after 100 h of mechanical milling of the mixtures of the elemental powders. The crystallization behavior of the alloys was also studied by transmission electron microscopy. Upon heating up to a temperature of the first exothermic peak,α-Al crystals precipitated from the amorphous Al84Fe16matrix. During crystallization of the Al82Fe18alloy, crystals of the Al6Fe intermetallic compound formed along withα-Al crystals. Substitution of Y for 2 at.% of Al in the Al82Fe16Y2alloy made crystallization of the alloy more complicated:α-Al, Al6Fe, and Fe4Y crystals coexisted with an amorphous phase. The activation energies corresponding to the fir...

Research paper thumbnail of Structural Investigations of TiC–Cu Nanocomposites Prepared by Ball Milling and Spark Plasma Sintering

Metals, 2017

In this work, TiC-Cu composites containing 20 and 30 vol % of nano-sized titanium carbide (TiC) p... more In this work, TiC-Cu composites containing 20 and 30 vol % of nano-sized titanium carbide (TiC) particles were prepared by powder metallurgy using copper powders with micrometer-sized and nanometer-sized particles. Mixtures of TiC and Cu powders were ball milled for 10 h and spark plasma sintered at 800-900 • C under an applied pressure of 50 MPa. The relative density of the sintered composites was 95.0%-96.5%. The composites fractured in a ductile mode. The crystallite size of the copper matrix in the composites prepared using the nanometer-sized copper powder was smaller than that in composites prepared using the micrometer-sized copper powder, which was confirmed by transmission electron microscopy (TEM). The hardness of the composites increased as the sintering temperature was increased from 800 to 900 • C. When the TiC content increased from 20 to 30 vol %, the hardness of the composites obtained from the micrometer-sized copper powder and sintered at 900 • C increased from 284 to 315 HV, while in composites obtained from the nanometer-sized copper, the hardness decreased from 347 to 337 HV.

Research paper thumbnail of Characterization of In-Situ Cu–TiH2–C and Cu–Ti–C Nanocomposites Produced by Mechanical Milling and Spark Plasma Sintering

Metals, 2017

This study focuses on the fabrication and microstructural investigation of Cu-TiH2-C and Cu-TiC n... more This study focuses on the fabrication and microstructural investigation of Cu-TiH2-C and Cu-TiC nanocomposites with different volume fractions (10% and 20%) of TiC. Two mixtures of powders were ball milled for 10 h, consequently consolidated by spark plasma sintering (SPS) at 900 and 1000 • C producing bulk materials with relative densities of 95-97%. The evolution process of TiC formation during sintering process was studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM). XRD patterns of composites present only Cu and TiC phases, no residual Ti phase can be detected. TEM images of composites with (10 vol % TiC) sintered at 900 • C show TiC nanoparticles about 10-30 nm precipitated in copper matrix, most of Ti and C dissolved in the composite matrix. At the higher sintering temperature of 1000 • C, more TiC precipitates from Cu-TiH2-C than those of Cu-TiC composite, particle size ranges from 10 to 20 nm. The hardness of both nanocomposites also increased with increasing sintering temperature. The highest hardness values of Cu-TiH2-C and Cu-TiC nanocomposites sintered at 1000 • C are 314 and 306 HV, respectively.

Research paper thumbnail of 고에너지 밀링 및 합성반응에 의한 Fe-TiC 복합분말 제조

Journal of Korean Powder Metallurgy Institute, 2013

TiB 2-reinforced iron matrix composite (Fe-TiB 2) powder was in-situ fabricated from titanium hyd... more TiB 2-reinforced iron matrix composite (Fe-TiB 2) powder was in-situ fabricated from titanium hydride (TiH 2) and iron boride (FeB) powders by the mechanical activation and a subsequent reaction. Phase formation of the composite powder was identified by X-ray diffraction (XRD). The morphology and phase composition were observed and measured by field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The results showed that TiB 2 particles formed in nanoscale were uniformly distributed in Fe matrix. Fe 2 B phase existed due to an incomplete reaction of Ti and FeB. Effect of milling process and synthesis temperature on the formation of composite were discussed.

Research paper thumbnail of Consolidation and Mechanical Properties of Mechanically Alloyed Al-Mg Powders

MRS Proceedings, 2008

Nanostructured Al-Mg bulk samples with compositions in the range of 10 – 40 at.% Mg have been pro... more Nanostructured Al-Mg bulk samples with compositions in the range of 10 – 40 at.% Mg have been produced by consolidation of mechanical alloyed powders. Powders with composition Al90Mg10 and Al80Mg20 were consolidated into highly dense specimens by hot extrusion. Room temperature compression tests for the Al90Mg10 specimen reveal interesting mechanical properties, namely, a high strength of 630 MPa combined with a plastic strain of about 4 %. The increase of the Mg content to 20 at.% increases the strength by about 100 MPa but it suppresses plastic deformation. The Al60Mg40 powder was consolidated at different temperatures by spark plasma sintering and the effect of the sintering temperature on microstructure, density and hardness have been studied. The results reveal that both density and hardness of the consolidated samples increase with increasing sintering temperature, while retaining a nanocrystalline structure. These results indicate that powder metallurgy is a suitable processi...

Research paper thumbnail of Thermal Stability of Amorphous Al-Fe-Y Prepared by Mechanical Alloying

Materials Science Forum, 2014

Al-Fe-Y amorphous alloys of Al84Fe16, Al82Fe18 and Al82Fe16Y2 composition were prepared by mechan... more Al-Fe-Y amorphous alloys of Al84Fe16, Al82Fe18 and Al82Fe16Y2 composition were prepared by mechanical alloying in a planetary ball mill P100. A nearly complete amorphization could be achieved for the Al84Fe16, Al82Fe18 and Al82Fe16Y2 powder alloys after 100h of milling at a rotational speed of 350 rpm in hexane medium. Differential scanning calorimetry (DSC) analyses revealed three-stage crystallization processes for Al82Fe18 and Al82Fe16Y2 alloys and four-stage crystallization processes for Al84Fe16 alloy, respectively. Taking into account the DSC data, the thermal stability increased in the order of Al84Fe16, Al82Fe18, and Al82Fe16Y2 composition. The Al82Fe16Y2 alloy exhibited a relatively better thermal stability than the other two alloys.

Research paper thumbnail of Synthesis and Characterization of Cu–TiC Nanocomposites by Ball Milling and Spark Plasma Sintering

Materials Science Forum, 2014

In this study, Cu-TiC nanocomposites were fabricated from a mixture of Cu and 5÷15% wt. TiC powde... more In this study, Cu-TiC nanocomposites were fabricated from a mixture of Cu and 5÷15% wt. TiC powders by ball milling and subsequent spark-plasma sintering. The morphology of Cu-TiC nanocomposite powders were observed by field emission scanning electron microscopy. Only characteristic peaks of Cu and TiC phases were detected from X-ray diffraction patterns of milled powder mixture. Sintered compacts showed a highly densified compacts (∼95% relative density) while retaining fine grains in the matrix. The hardness, wear resistance, and fracture surface of the sintered specimens were also investigated.

Research paper thumbnail of High-strength Al87Ni8La5 bulk alloy produced by spark plasma sintering of gas atomized powders

Journal of Materials Research, 2009

In situ devitrification and consolidation of gas atomized Al87Ni8La5 glassy powders into highly d... more In situ devitrification and consolidation of gas atomized Al87Ni8La5 glassy powders into highly dense bulk specimens was carried out by spark plasma sintering. Room temperature compression tests of the consolidated bulk material reveal remarkable mechanical properties, namely, high compression strength of 930 MPa combined with plastic strain exceeding 25%. These findings demonstrate that the combined devitrification and consolidation of glassy precursors by spark plasma sintering is a suitable method for the production of Al-based materials characterized by high strength and considerable plastic deformation.

Research paper thumbnail of Amorphous Ti–Cu–Ni–Al alloys prepared by mechanical alloying

Journal of Materials Science, 2009

Ti x (CuNi)90–x Al10 (x = 50, 55, 60) amorphous powder alloys were synthesized by mechanical allo... more Ti x (CuNi)90–x Al10 (x = 50, 55, 60) amorphous powder alloys were synthesized by mechanical alloying technique. The evolution of amorphization during milling and subsequent heat treatment was investigated by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The fully amorphous powders were obtained in the Ti50Cu20Ni20Al10, Ti55Cu17.5Ni17.5Al10 and Ti60Cu15Ni15Al10 alloys after milling for 30, 20 and 15 h, respectively. Differential scanning calorimetry revealed that thermal stability increased with the increasing (CuNi) content: Ti60Cu15Ni15Al10, Ti55Cu17.5Ni17.5Al10 and Ti50Cu20Ni20Al10. Heating of the three amorphous alloys at 800 K for 10 min results in the formation of the NiTi, NiTi2 and CuTi2 intermetallic phases.

Research paper thumbnail of Spark plasma sintering of gas atomized Al 87 Ni 8 La 5 amorphous powder

Journal of Physics: Conference Series, 2009

Bulk samples were prepared by in-situ devitrification and consolidation of gas atomized Al 87 Ni ... more Bulk samples were prepared by in-situ devitrification and consolidation of gas atomized Al 87 Ni 8 La 5 amorphous powder. Consolidation was carried out at different temperatures by spark plasma sintering, which leads to highly dense bulk specimens with a microstructure consisting of fcc aluminum together with Al 11 La 3 and Al 3 Ni intermetallic compounds. The consolidated powder displays a remarkably high compression stress, which depends on the sintering temperature and ranges between 900 and 1000 MPa, combined with plastic strain varying between 10 and 20 %. These results indicate that the mechanical properties of the samples can be tuned within a wide range of strength and ductility as a function of the sintering temperature used.

Research paper thumbnail of Structural characterization and magnetic properties of Al 82 Fe 16 TM 2 (TM: Ti, Ni, Cu) alloys prepared by mechanical alloying

A B S T R A C T In this work, the structural evolution of Al–16 at.%Fe–2 at.%TM (Transition Metal... more A B S T R A C T In this work, the structural evolution of Al–16 at.%Fe–2 at.%TM (Transition Metals (TM): Ti, Ni, Cu) alloys during mechanical alloying and their magnetic properties were investigated. The evolution of the phase composition and microstructure of the alloys with the milling time was studied using X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The phase composition of the alloys was determined using the Rietveld refinement of the XRD profiles. It was shown that the interaction between the components of the powder mixtures during milling started with dissolution of Fe in the Al crystalline lattice and Al in the Fe crystalline lattice. Upon further milling, ferromagnetic AlFe 3 (DO3) formed and further transformed into paramagnetic bcc-AlFe and later into an amorphous phase. It was found that the TM alloying elements significantly influence the kinetics of the transformations during milling: the Al 82 Fe 16 Ti 2 alloy was fully amorphous after 40 h of milling, the Al 82 Fe 16 Ni 2 alloy required 50 h of milling to achieve complete amorphization, and the Al 82 Fe 16 Cu 2 alloy was only partially amorphous after 60 h of milling. The interpretation of the observed alloying effect has been proposed. The magnetic properties of the alloys were correlated with the results of the structural characterization.

Research paper thumbnail of Structural Investigations of TiC–Cu Nanocomposites Prepared by Ball Milling and Spark Plasma Sintering

In this work, TiC–Cu composites containing 20 and 30 vol % of nano-sized titanium carbide (TiC) p... more In this work, TiC–Cu composites containing 20 and 30 vol % of nano-sized titanium carbide (TiC) particles were prepared by powder metallurgy using copper powders with micrometer-sized and nanometer-sized particles. Mixtures of TiC and Cu powders were ball milled for 10 h and spark plasma sintered at 800–900 • C under an applied pressure of 50 MPa. The relative density of the sintered composites was 95.0%–96.5%. The composites fractured in a ductile mode. The crystallite size of the copper matrix in the composites prepared using the nanometer-sized copper powder was smaller than that in composites prepared using the micrometer-sized copper powder, which was confirmed by transmission electron microscopy (TEM). The hardness of the composites increased as the sintering temperature was increased from 800 to 900 • C. When the TiC content increased from 20 to 30 vol %, the hardness of the composites obtained from the micrometer-sized copper powder and sintered at 900 • C increased from 284 to 315 HV, while in composites obtained from the nanometer-sized copper, the hardness decreased from 347 to 337 HV.

Research paper thumbnail of Characterization of In-Situ Cu–TiH2–C and Cu–Ti–C Nanocomposites Produced by Mechanical Milling and Spark Plasma Sintering

This study focuses on the fabrication and microstructural investigation of Cu–TiH2–C and Cu–Ti–C ... more This study focuses on the fabrication and microstructural investigation of Cu–TiH2–C and Cu–Ti–C nanocomposites with different volume fractions (10% and 20%) of TiC. Two mixtures of powders were ball milled for 10 h, consequently consolidated by spark plasma sintering (SPS) at 900 and 1000 • C producing bulk materials with relative densities of 95–97%. The evolution process of TiC formation during sintering process was studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM). XRD patterns of composites present only Cu and TiC phases, no residual Ti phase can be detected. TEM images of composites with (10 vol % TiC) sintered at 900 • C show TiC nanoparticles about 10–30 nm precipitated in copper matrix, most of Ti and C dissolved in the composite matrix. At the higher sintering temperature of 1000 • C, more TiC precipitates from Cu–TiH2–C than those of Cu–Ti–C composite, particle size ranges from 10 to 20 nm. The hardness of both nanocomposites also increased with increasing sintering temperature. The highest hardness values of Cu–TiH2–C and Cu–Ti–C nanocomposites sintered at 1000 • C are 314 and 306 HV, respectively.

Research paper thumbnail of Crystallization Kinetics of Al-Fe and Al-Fe-Y Amorphous Alloys Produced by Mechanical Milling

In this work, the effect of a slight change in the composition of the Al-Fe amorphous alloys (fro... more In this work, the effect of a slight change in the composition of the Al-Fe amorphous alloys (from Al 84 Fe 16 to Al 82 Fe 18) and the substitution of Y for Al (2 at.%) on their crystallization kinetics was studied. According to the X-ray diffraction analysis, powders of the Al 84 Fe 16 , Al 82 Fe 18 , and Al 82 Fe 16 Y 2 alloys with a fully amorphous structure were formed after 100 h of mechanical milling of the mixtures of the elemental powders. The crystallization behavior of the alloys was also studied by transmission electron microscopy. Upon heating up to a temperature of the first exothermic peak, í µí»¼-Al crystals precipitated from the amorphous Al 84 Fe 16 matrix. During crystallization of the Al 82 Fe 18 alloy, crystals of the Al 6 Fe intermetallic compound formed along with í µí»¼-Al crystals. Substitution of Y for 2 at.% of Al in the Al 82 Fe 16 Y 2 alloy made crystallization of the alloy more complicated: í µí»¼-Al, Al 6 Fe, and Fe 4 Y crystals coexisted with an amorphous phase. The activation energies corresponding to the first crystallization event of the alloys were calculated using the Kissinger and Ozawa methods. The values obtained by these two methods were in good agreement with each other and the same trends of changing with the alloy composition were observed. The Avrami exponent í µí±› was determined from the Johnson-Mehl-Avrami equation and showed that crystallization at the first stage is interface-controlled growth for all the three powder alloys studied.