The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying...The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying the composition, i.e. fully or partially replacing rare earth （RE） and transition metal （TM） elements based on similar atomic radii and coordination number. X-ray diffraction and high resolution transmission electron microscopy study revealed that the amorphization process occurred through formation of various intermetallic phases and nanocrystalline FCC Al. Fully amorphous phase was obtained for the alloys not containing lanthanum, whereas the other alloys containing La showed partial amorphization with reappearance of intermetallic phases attributed to mechanical crystallization. Differential scanning calorimetry study confirmed better thermal stability with wider transformation temperature for the alloys without La.展开更多
In the present study,Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) bulk amorphous nanocomposites were synthesized by spark plasma sintering of milled melt spun ribbon particles.The as-cast ribbons were of ...In the present study,Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) bulk amorphous nanocomposites were synthesized by spark plasma sintering of milled melt spun ribbon particles.The as-cast ribbons were of near amorphous nature with minute amount of FCC Al embedded in the amorphous matrix.Milling of the ribbons resulted in partial devitrifi cation due to mechanical crystallization.The milled ribbon particles were sintered in the temperature and pressure range of 300-500℃ and 500-700 MPa,respectively.It was observed that nominal amount of amorphous phase was retained at 500℃ and 500 MPa.With increase in sintering pressure and decrease in sintering temperature,the amount of crystalline phase evolution decreased,and maximum amount of amorphous phase was retained at 300℃ and 700 MPa.The microstructure consisting of amorphous phase embedded with hard intermetallic phases led to increase in the nanohardness of Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) as-cast ribbons from 3.26±0.59 GPa and 3.81±0.58 GPa to 6.06±0.70 GPa and 6.14±0.82 GPa,respectively,for the corresponding consolidated amorphous nanocomposite.Microhardness of the three and five component system bulk samples was 4.19±0.13GPa and 3.6±0.13 GPa,respectively.展开更多
Powder mixture of ball-milled aluminium and functionalized multi-walled carbon nanotubes was compacted via spark plasma sintering （SPS） to study effects of sintering temperature and heating rate. An increase in sint...Powder mixture of ball-milled aluminium and functionalized multi-walled carbon nanotubes was compacted via spark plasma sintering （SPS） to study effects of sintering temperature and heating rate. An increase in sintering temperature led to an increase in crystallite size and density, whereas an increase in heating rate exerted the opposite effect. The crystallite size and relative density increased by 85.0% and 14.3%, respectively, upon increasing the sintering temperature from 400 to 600℃, whereas increasing the heating rate from 25 to 100 ℃/min led to respective reduction by 30.0% of crystallite size and 1.8% of relative density. The total punch displacement during SPS for the nanocomposite sintered at 600 ℃ （1.96 mm） was much higher than that of the sample sintered at 400 ℃ （1.02 mm） confirming positive impact of high sintering temperature on densification behaviour. The maximum improvement in mechanical properties was exhibited by the nanocomposite sintered at 600 ℃ at a heating rate of 50℃/min displaying microhardness of 81 4- 3.6 VHN and elastic modulus of 89 4- 5.3 GPa. The nanocomposites consolidated at 400 ℃ and 100 ℃/min, in spite of having relatively smaller crystallite size, exhibited poor mechanical properties indicating the detrimental effect of porosity on the mechanical properties.展开更多
基金financial support obtained from the Science and Engineering Research Board,Department of Science & Technology,Government of India(SB/S3/ME/0044/2013)Sponsored Research and Industrial Consultancy,Indian Institute of Technology Kharagpur,India(GAF)
文摘The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying the composition, i.e. fully or partially replacing rare earth （RE） and transition metal （TM） elements based on similar atomic radii and coordination number. X-ray diffraction and high resolution transmission electron microscopy study revealed that the amorphization process occurred through formation of various intermetallic phases and nanocrystalline FCC Al. Fully amorphous phase was obtained for the alloys not containing lanthanum, whereas the other alloys containing La showed partial amorphization with reappearance of intermetallic phases attributed to mechanical crystallization. Differential scanning calorimetry study confirmed better thermal stability with wider transformation temperature for the alloys without La.
基金was fi nancially supported by the Science and Engineering Research Board,Department of Science&Technology,Government of India(Grant No.SB/S3/ME/0044/2013)。
文摘In the present study,Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) bulk amorphous nanocomposites were synthesized by spark plasma sintering of milled melt spun ribbon particles.The as-cast ribbons were of near amorphous nature with minute amount of FCC Al embedded in the amorphous matrix.Milling of the ribbons resulted in partial devitrifi cation due to mechanical crystallization.The milled ribbon particles were sintered in the temperature and pressure range of 300-500℃ and 500-700 MPa,respectively.It was observed that nominal amount of amorphous phase was retained at 500℃ and 500 MPa.With increase in sintering pressure and decrease in sintering temperature,the amount of crystalline phase evolution decreased,and maximum amount of amorphous phase was retained at 300℃ and 700 MPa.The microstructure consisting of amorphous phase embedded with hard intermetallic phases led to increase in the nanohardness of Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) as-cast ribbons from 3.26±0.59 GPa and 3.81±0.58 GPa to 6.06±0.70 GPa and 6.14±0.82 GPa,respectively,for the corresponding consolidated amorphous nanocomposite.Microhardness of the three and five component system bulk samples was 4.19±0.13GPa and 3.6±0.13 GPa,respectively.
基金supported financially by the‘‘SERC Funding’’ from Department of Science and Technology,Government of India(No.SERC/ET-0388/2012)
文摘Powder mixture of ball-milled aluminium and functionalized multi-walled carbon nanotubes was compacted via spark plasma sintering （SPS） to study effects of sintering temperature and heating rate. An increase in sintering temperature led to an increase in crystallite size and density, whereas an increase in heating rate exerted the opposite effect. The crystallite size and relative density increased by 85.0% and 14.3%, respectively, upon increasing the sintering temperature from 400 to 600℃, whereas increasing the heating rate from 25 to 100 ℃/min led to respective reduction by 30.0% of crystallite size and 1.8% of relative density. The total punch displacement during SPS for the nanocomposite sintered at 600 ℃ （1.96 mm） was much higher than that of the sample sintered at 400 ℃ （1.02 mm） confirming positive impact of high sintering temperature on densification behaviour. The maximum improvement in mechanical properties was exhibited by the nanocomposite sintered at 600 ℃ at a heating rate of 50℃/min displaying microhardness of 81 4- 3.6 VHN and elastic modulus of 89 4- 5.3 GPa. The nanocomposites consolidated at 400 ℃ and 100 ℃/min, in spite of having relatively smaller crystallite size, exhibited poor mechanical properties indicating the detrimental effect of porosity on the mechanical properties.
