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Sivasankaran S.,Indian National Institute of Engineering | Sivaprasad K.,National Institute of Technology Tiruchirappalli | Narayanasamy R.,Indian National Institute of Engineering | Iyer V.K.,Powder Metallurgy Shop
Journal of Alloys and Compounds | Year: 2010

Manufacturing of 6061 Al alloy reinforced with different weight percentages of TiO2 metal matrix composite powder through low-energy and high-energy ball milling for microcomposites and nanocomposites respectively followed by cold uniaxial compaction and sintering was investigated. The milled powder was characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and differential thermal analyzer. No intermetallic compounds were observed during high-energy ball milling by wet method, but petite iron contamination was present due to vial media after 40 h milling. The crystallite size of about 46 nm was obtained in the case of high reinforcement content. Powder surface morphology, crystallite size as a function of chemical composition and milling time, and lattice parameter of the high-energy ball-milled powder were examined. The effect of matrix-to-reinforcement particle size ratio on the green compressive strength for both composites was also investigated. The green pellets were degassed at 350 °C for 60 min, and then sintered in the temperature steps of 475, 550 and 625 °C under reducing atmosphere for 120 min. The effects of reinforcement content on densification as percentage theoretical density, sinterability and Vickers hardness of the composites were also studied. The results revealed that the sinterability improved as the percentage of reinforcement increased for nanocomposites whereas it worsened for microcomposites. The nanocomposites exhibited a high Vickers hardness of 1126 MPa, which was around 3-4 times higher than that of microcomposites. © 2009 Elsevier B.V. All rights reserved.


Sivasankaran S.,National Institute of Technology Tiruchirappalli | Sivaprasad K.,National Institute of Technology Tiruchirappalli | Narayanasamy R.,National Institute of Technology Tiruchirappalli | Iyer V.K.,Powder Metallurgy Shop
Powder Technology | Year: 2011

Nanocrystallite/nanocomposite powders of AA 6061 100-x-x wt.% TiO 2 (x=0, 2, 4, 6, 8, 10 and 12) prepared by mechanical alloying and compacted at room temperature have been used for the present investigation. Compaction behavior of post-compacts as a function of compaction pressure and the nano titania content in the nanocrystallite matrix powder was investigated using several powder compaction equations (empirical form) including both linear and non-linear type. The non-linear equation proposed by Van Der Zwan and Siskens was the best fitting curve comparing other equations developed by Balshin, Heckel, Ge, Panelli and Ambrosio Filho, Kawakita, and Shapiro. The Van Der Zwan and Siskens compacting equation gives the regression coefficient very close to unity. Also, this paper focuses on the development of expert system based on an adaptive neuro-fuzzy inference system (ANFIS) on compaction behavior of the developed nanocomposite powder. This ANFIS model was accurately established to obtain the relationship between percentage of nano titania content in the nanocrystalline matrix and compaction pressure to get the required relative density. The predicted relative density obtained from ANFIS was compared with experimental data and also evaluated with the predicted relative density derived by multiple regression analysis (MRA). The comparisons indicated that the developed ANFIS achieved excellent accuracy and it was as high as 99.50%. © 2011 Elsevier B.V.


Jeyasimman D.,National Institute of Technology Tiruchirappalli | Sivaprasad K.,National Institute of Technology Tiruchirappalli | Sivasankaran S.,Coimbatore Institute of Technology | Ponalagusamy R.,National Institute of Technology Tiruchirappalli | And 2 more authors.
Advanced Powder Technology | Year: 2015

AA 6061 nanocomposites of nanocrystallite powders reinforced with nano-alumina particles were synthesized and investigated in this study. A uniform distribution of nano γ-Al2O3 in the AA 6061 nanocrystallite matrix was successfully obtained after 30 h of mechanical alloying (MA). The compressibility and sinterability of the prepared nanocomposite powders at varying sintering temperatures and varying compaction pressures was also studied. The consolidation behaviour of the AA 6061/γ-Al2O3 nanocomposites was evaluated using the Balshin, Heckel, Panelli and Ambrosio Filho, and Ge linear compaction equations. The compression strength of the green samples and the Vickers hardness of the nanocomposites were also evaluated. A maximum green compression strength of 176 MPa and a maximum hardness of 740 MPa were obtained for the addition of 2 wt.% Al2O3 nanoparticles to the AA 6061 matrix after 30 h of MA. © 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.


Sivasankaran S.,National Institute of Technology Tiruchirappalli | Sivaprasad K.,National Institute of Technology Tiruchirappalli | Narayanasamy R.,National Institute of Technology Tiruchirappalli | Satyanarayana P.V.,Powder Metallurgy Shop
Materials Characterization | Year: 2011

Nanocrystalline AA 6061 alloy reinforced with alumina (0, 4, 8, and 12 wt.%) in amorphized state composite powder was synthesized by mechanical alloying and consolidated by conventional powder metallurgy route. The as-milled and as-sintered (573 K and 673 K) nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The peaks corresponding to fine alumina was not observed by XRD patterns due to amorphization. Using high-resolution transmission electron microscope, it is confirmed that the presence of amorphized alumina observed in Al lattice fringes. The crystallite size, lattice strain, deformation stress, and strain energy density of AA 6061 matrix were determined precisely from the first five most intensive reflection of XRD using simple Williamson-Hall models; uniform deformation model, uniform stress deformation model, and uniform energy density deformation model. Among the developed models, uniform energy density deformation model was observed to be the best fit and realistic model for mechanically alloyed powders. This model evidenced the more anisotropic nature of the ball milled powders. The XRD peaks of as-milled powder samples demonstrated a considerable broadening with percentage of reinforcement due to grain refinement and lattice distortions during same milling time (40 h). The as-sintered (673 K) unreinforced AA 6061 matrix crystallite size from well fitted uniform energy density deformation model was 98 nm. The as-milled and as-sintered (673 K) nanocrystallite matrix sizes for 12 wt.% Al 2O3 well fitted by uniform energy density deformation model were 38 nm and 77 nm respectively, which indicate that the fine Al 2O3 pinned the matrix grain boundary and prevented the grain growth during sintering. Finally, the lattice parameter of Al matrix in as-milled and as-sintered conditions was also investigated in this paper. © 2011 Elsevier Inc.


Jeyasimman D.,National Institute of Technology Tiruchirappalli | Sivasankaran S.,Coimbatore Institute of Technology | Sivaprasad K.,National Institute of Technology Tiruchirappalli | Narayanasamy R.,National Institute of Technology Tiruchirappalli | Kambali R.S.,Powder Metallurgy Shop
Materials and Design | Year: 2014

Nanostructured Al 6061- xwt.% TiC (x= 0.5, 1.0, 1.5 and 2.0. wt.%) composites were synthesised by mechanical alloying with a milling time of 30. h. The milled powders were consolidated by cold uniaxial compaction followed by sintering at various temperatures (723, 798 and 873. K). The uniform distribution and dispersion of TiC particles in the Al 6061 matrix was confirmed by characterising these nanocomposite powders by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The mechanical properties, specifically the green compressive strength and hardness, were tested. A maximum hardness of 1180. MPa was obtained for the Al 6061-2. wt.% TiC nanocomposite sintered at 873. K, which was approximately four times higher than that of the Al 6061 microcrystalline material. A maximum green compressive strength of 233. MPa was obtained when 2. wt.% TiC was added. The effect of reinforcement on the densification was studied and reported in terms of the relative density, sinterability, green compressive strength, compressibility and Vickers hardness of the nanocomposites. The compressibility curves of the developed nanocomposite powders were also plotted and investigated using the Heckel, Panelli and Ambrosio Filho and Ge equations. © 2014 Elsevier Ltd.

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