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38 results on '"Makineni, S."'

1. On the effect of Re addition on microstructural evolution of a CoNi-based superalloy

Author

Pandey, P., Sawant, A. K., Nithin, B., Peng, Z., Makineni, S. K., Gault, B., and Chattopadhyay, K.

Subjects
Condensed Matter - Materials Science
Abstract

In this study, the effect of rhenium (Re) addition on microstructural evolution of a new low-density Co-Ni-Al-Mo-Nb based superalloy is presented. Addition of Re significantly influences the {\gamma}' precipitate morphology, the {\gamma}/{\gamma}' lattice misfit and the {\gamma}/{\gamma}' microstructural stability during long term aging. An addition of 2 at.% Re to a Co-30Ni-10Al-5Mo-2Nb (all in at.%) alloy, aged at 900{\deg}C for 50 hours, reduces the {\gamma}/{\gamma}' lattice misfit by {\approx} 40% (from +0.32% to +0.19%, measured at room temperature) and hence alters the {\gamma}' morphology from cuboidal to round-cornered cuboidal precipitates. The composition profiles across the {\gamma}/{\gamma}' interface by atom probe tomography (APT) reveals Re partitions to the {\gamma} phase (K_Re=0.34) and also results in the partitioning reversal of Mo to the {\gamma} phase (K_Mo=0.90) from the {\gamma}' precipitate. An inhomogeneous distribution of Gibbsian interfacial excess for the solute Re ({\Gamma}_Re, ranging from 0.8 to 9.6 atom.nm-2) has been observed at the {\gamma}/{\gamma}' interface. A coarsening study at 900{\deg}C (up to 1000 hours) suggests that the coarsening of {\gamma}' precipitates occurs solely by an evaporation--condensation (EC) mechanism. This is contrary to that observed in the Co-30Ni-10Al-5Mo-2Nb alloy as well as in some of the Ni-Al based and high mass density Co-Al-W based superalloys, where {\gamma}' precipitates coarsen by coagulation/coalescence mechanism with extensive alignment of {\gamma}' along <100> directions as a sign of microstructural instability. The {\gamma}' coarsening rate exponent (K_r) and {\gamma}/{\gamma}' interfacial energy are estimated to be 1.41 x 10-27 m3/s and 8.4 mJ/m2, which are comparable and lower than Co-Al-W based superalloys.

Published
2019
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5. Constraint-Aware Large-Scale CMP Cache Design

Author

Zhao, L., Iyer, R., Makineni, S., Illikkal, R., Moses, J., Newell, D., Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Aluru, Srinivas, editor, Parashar, Manish, editor, Badrinath, Ramamurthy, editor, and Prasanna, Viktor K., editor

Published
2007
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12. TCP onloading for data center servers

Author

Regnier, G., primary, Makineni, S., additional, Illikkal, I., additional, Iyer, R., additional, Minturn, D., additional, Huggahalli, R., additional, Newell, D., additional, Cline, L., additional, and Foong, A., additional

Published
2004
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25. Synthesis and Antibacterial Properties of Some Tripeptides1

Author

Makineni S, Shankman S, Noll W, and Higa S

Subjects
chemistry.chemical_classification, Biochemistry, biology, Chemistry, Lactobacillus, Drug Discovery, Molecular Medicine, Pediococcus, Tripeptide, biology.organism_classification, Amino acid
Published
1963

26. Characterising precipitate evolution in multi-component cast aluminium alloys using small-angle X-ray scattering

Author

Panagos, P., Wang, Y., McCartney, D.G., Li, M., Ghaffari, B., Zindel, J.W., Miao, J., Makineni, S., Allison, J.E., Shebanova, O., Robson, J.D., Lee, Peter D., Panagos, P., Wang, Y., McCartney, D.G., Li, M., Ghaffari, B., Zindel, J.W., Miao, J., Makineni, S., Allison, J.E., Shebanova, O., Robson, J.D., and Lee, Peter D.

Abstract

Aluminium alloys can be strengthened significantly by nano-scale precipitates that restrict dislocation movement. In this study, the evolution of inhomogenously distributed trialuminide precipitates in two multi component alloys was characterised by synchrotron small angle Xray scattering (SAXS). The appropriate selection of reference sample and data treatment required to successfully characterise a low volume fraction of precipitates in multi-component alloys via SAXS was investigated. The resulting SAXS study allowed the analysis of statistically significant numbers of precipitates (billions) as compared to electron microscopy (hundreds). Two cast aluminium alloys with different volume fractions of Al3ZrxV1-x precipitates were studied. Data analysis was conducted using direct evaluation methods on SAXS spectra and the results compared with those from transmission electron microscopy (TEM). Precipitates were found to attain a spherical structure with homogeneous chemical composition. Precipitate evolution was quantified, including size, size distribution, volume fraction and number density. The results provide evidence that these multi-component alloys have a short nucleation stage, with coarsening dominating precipitate size. The coarsening rate constant was calculated and compared to similar precipitate behaviour.

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27. Characterising precipitate evolution in multi-component cast aluminium alloys using small-angle X-ray scattering

Author

Panagos, P., Wang, Y., McCartney, D.G., Li, M., Ghaffari, B., Zindel, J.W., Miao, J., Makineni, S., Allison, J.E., Shebanova, O., Robson, J.D., Lee, Peter D., Panagos, P., Wang, Y., McCartney, D.G., Li, M., Ghaffari, B., Zindel, J.W., Miao, J., Makineni, S., Allison, J.E., Shebanova, O., Robson, J.D., and Lee, Peter D.

Abstract

Aluminium alloys can be strengthened significantly by nano-scale precipitates that restrict dislocation movement. In this study, the evolution of inhomogenously distributed trialuminide precipitates in two multi component alloys was characterised by synchrotron small angle Xray scattering (SAXS). The appropriate selection of reference sample and data treatment required to successfully characterise a low volume fraction of precipitates in multi-component alloys via SAXS was investigated. The resulting SAXS study allowed the analysis of statistically significant numbers of precipitates (billions) as compared to electron microscopy (hundreds). Two cast aluminium alloys with different volume fractions of Al3ZrxV1-x precipitates were studied. Data analysis was conducted using direct evaluation methods on SAXS spectra and the results compared with those from transmission electron microscopy (TEM). Precipitates were found to attain a spherical structure with homogeneous chemical composition. Precipitate evolution was quantified, including size, size distribution, volume fraction and number density. The results provide evidence that these multi-component alloys have a short nucleation stage, with coarsening dominating precipitate size. The coarsening rate constant was calculated and compared to similar precipitate behaviour.

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28. Characterising precipitate evolution in multi-component cast aluminium alloys using small-angle X-ray scattering

Author

Panagos, P., Wang, Y., McCartney, D.G., Li, M., Ghaffari, B., Zindel, J.W., Miao, J., Makineni, S., Allison, J.E., Shebanova, O., Robson, J.D., Lee, Peter D., Panagos, P., Wang, Y., McCartney, D.G., Li, M., Ghaffari, B., Zindel, J.W., Miao, J., Makineni, S., Allison, J.E., Shebanova, O., Robson, J.D., and Lee, Peter D.

Abstract

Aluminium alloys can be strengthened significantly by nano-scale precipitates that restrict dislocation movement. In this study, the evolution of inhomogenously distributed trialuminide precipitates in two multi component alloys was characterised by synchrotron small angle Xray scattering (SAXS). The appropriate selection of reference sample and data treatment required to successfully characterise a low volume fraction of precipitates in multi-component alloys via SAXS was investigated. The resulting SAXS study allowed the analysis of statistically significant numbers of precipitates (billions) as compared to electron microscopy (hundreds). Two cast aluminium alloys with different volume fractions of Al3ZrxV1-x precipitates were studied. Data analysis was conducted using direct evaluation methods on SAXS spectra and the results compared with those from transmission electron microscopy (TEM). Precipitates were found to attain a spherical structure with homogeneous chemical composition. Precipitate evolution was quantified, including size, size distribution, volume fraction and number density. The results provide evidence that these multi-component alloys have a short nucleation stage, with coarsening dominating precipitate size. The coarsening rate constant was calculated and compared to similar precipitate behaviour.

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29. Characterising precipitate evolution in multi-component cast aluminium alloys using small-angle X-ray scattering

Author

Panagos, P., Wang, Y., McCartney, D.G., Li, M., Ghaffari, B., Zindel, J.W., Miao, J., Makineni, S., Allison, J.E., Shebanova, O., Robson, J.D., Lee, Peter D., Panagos, P., Wang, Y., McCartney, D.G., Li, M., Ghaffari, B., Zindel, J.W., Miao, J., Makineni, S., Allison, J.E., Shebanova, O., Robson, J.D., and Lee, Peter D.

Abstract

Aluminium alloys can be strengthened significantly by nano-scale precipitates that restrict dislocation movement. In this study, the evolution of inhomogenously distributed trialuminide precipitates in two multi component alloys was characterised by synchrotron small angle Xray scattering (SAXS). The appropriate selection of reference sample and data treatment required to successfully characterise a low volume fraction of precipitates in multi-component alloys via SAXS was investigated. The resulting SAXS study allowed the analysis of statistically significant numbers of precipitates (billions) as compared to electron microscopy (hundreds). Two cast aluminium alloys with different volume fractions of Al3ZrxV1-x precipitates were studied. Data analysis was conducted using direct evaluation methods on SAXS spectra and the results compared with those from transmission electron microscopy (TEM). Precipitates were found to attain a spherical structure with homogeneous chemical composition. Precipitate evolution was quantified, including size, size distribution, volume fraction and number density. The results provide evidence that these multi-component alloys have a short nucleation stage, with coarsening dominating precipitate size. The coarsening rate constant was calculated and compared to similar precipitate behaviour.

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37. Electric field-assisted resonance frequency tuning in free standing nanomechanical devices for application in multistate switching using a phase change material.

Author

Banswar D, Anand JK, Bukhari SA, Singh S, Prajesh R, Kumar H, Makineni SK, and Goswami A

Abstract

VO 2 possesses a unique property of solid-state phase transition near room temperature wherein it transforms from monoclinic (M1) to tetragonal phase (R) that alters its physical properties, such as resistivity, mechanical modulus, and lattice strain, at an ultrafast time scale known as MIT. Such a phenomenon offers a distinct advantage to use VO 2 in switching applications using heat flux as a stimulus. However, such alteration in properties can also be triggered under an electric field ( E ), which is known as E-MIT. A nanomechanical resonator coated with VO 2 recently received traction where the resonance behavior can be modulated by taking advantage of its phase transition. Herein, we demonstrate that by fabricating a microstring of 400 μm ( L ) × 5 μm ( W ) × 240 nm ( t ) of suspended SiN x coated with VO 2 , the frequency ( f r ) of the resonator can be modulated by applying an electric field. We show that at room temperature, the f r of the microstring can be either reduced (by 0.5% at 15 V mm -1 ) or enhanced (by 2.2% at 25 V mm -1 ) or can be varied in a cycle under E -field. Using theoretical models, we establish the simulated results and explain the processes behind it, which demonstrate excellent mechanical tuning properties of the VO 2 -based microstring resonator, making it an attractive and alternative option for highly efficient MEMS-based switches and neuromorphic devices.

Published
2024
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38. Enhancing elevated temperature strength of copper containing aluminium alloys by forming L1 2 Al 3 Zr precipitates and nucleating θ″ precipitates on them.

Author

Kumar Makineni S, Sugathan S, Meher S, Banerjee R, Bhattacharya S, Kumar S, and Chattopadhyay K

Abstract

Strengthening by precipitation of second phase is the guiding principle for the development of a host of high strength structural alloys, in particular, aluminium alloys for transportation sector. Higher efficiency and lower emission demands use of alloys at higher operating temperatures (200 °C-250 °C) and stresses, especially in applications for engine parts. Unfortunately, most of the precipitation hardened aluminium alloys that are currently available can withstand maximum temperatures ranging from 150-200 °C. This limit is set by the onset of the rapid coarsening of the precipitates and consequent loss of mechanical properties. In this communication, we present a new approach in designing an Al-based alloy through solid state precipitation route that provides a synergistic coupling of two different types of precipitates that has enabled us to develop coarsening resistant high-temperature alloys that are stable in the temperature range of 250-300 °C with strength in excess of 260 MPa at 250 °C.

Published
2017
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