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20150922150746.0 |
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121127s2012 txu obm 000 0 eng d |
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|a (OCoLC)ocn819407622
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|a (OCoLC)819407622
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|a (TxCM)http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-9881
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|a TXA
|c TXA
|d UtOrBLW
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|a TXAM
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|a 2011
|a Thesis
|a 1969.1/ETD-TAMU-2011-08-9881
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|a Chari, Arpita.
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|a Computational thermodynamics of CoNiGa high temperature shape memory alloys /
|c by Arpita Ramesh Chari.
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|a [College Station, Tex.] :
|b [Texas A&M University],
|c [2012]
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|a 1 online resource.
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|a text
|b txt
|2 rdacontent
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|a computer
|b c
|2 rdamedia
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|a online resource
|b cr
|2 rdacarrier
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|a "Major Subject: Mechanical Engineering"
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|a Description from author supplied metadata (automated record created 2012-10-22 13:24:58).
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| 502 |
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|b Master of Science
|c Texas A&M University
|d 2011
|o http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-9881
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|a Includes bibliographical references.
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|a Text (Thesis)
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|a Shape Memory Alloys (SMAs) are advanced materials with interesting properties such as pseudoelasticity (PE) and the shape memory effect (SME). Recently, the CoNiGa system has emerged as the basis for very promising High Temperature Shape Memory Alloys (HTSMAs), with possible applications in the aerospace and automotive industries. Although the CoNiGa system shows significant promise for its use as HTSMAs, limited studies are available on them. Hence, a more intensive investigation of these alloys is necessary to understand their phase stability over a wide range of temperature and compositions in order for further development of CoNiGa-based HTSMAs and future use of the model in alloy design. This formed the basis of motivation for the present work. In this work, a thermodynamic model of the ternary system is calculated based on the CALPHAD approach, to investigate the thermodynamic properties, phase stability and shape memory properties of these alloys. The CALPHAD approach is a computational method that enables the calculations of thermodynamic properties of systems. This method uses all available experimental and theoretical data in order to calculate the Gibbs energies of the phases in the system. The software used to carry out the calculations is "ThermoCalc," which is a computational software using CALPHAD principles, based on the minimization of Gibbs energy, and is enhanced by a global minimization technique on the system. The stability of the beta phase at high temperatures was enforced accurately by remodeling the CoGa system. The binary CoGa system that makes up the ternary was remodeled, as the beta phase (which is very important as it dominates the central region of the ternary CoNiGa system where the shape memory effect is observed), re-stabilizes as the temperature increases above the liquidus in the CoGa system. Phase relations and thermodynamic properties of the CoNiGa system based on all experimental information were evaluated. Different properties like enthalpies, activities, sublattice site fraction of vacancies and phase fractions calculated in the system matched well compared to the experimental information used to model the system. Also, the phase equilibria among the gamma (fcc), beta, gamma'(Ni3Ga), delta (Ni5Ga3) and epsilon (Ni13Ga9) were determined at various temperatures.
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|a Electronic resource.
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|a Major Mechanical Engineering.
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|a Shape Memory Alloys
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|a Computational Thermodynamics
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|a CoNiGa ternary
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|a Arroyave, Raymundo,
|e thesis advisor.
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|u http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-9881
|z Link to OAK Trust copy
|t 0
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| 994 |
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|a C0
|b TXA
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| 948 |
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|a cataloged
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|c 2012/11/27
|d o
|e agaffey
|f 9:39:44 am
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|a MARS
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|s 4ac3b42b-88f5-3dec-be2f-ef712e6ec28c
|i 3116675f-f4e9-32c8-a4ae-95b6f0712f23
|t 0
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| 952 |
f |
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|a Texas A&M University
|b College Station
|c Electronic Resources
|d Available Online
|t 0
|e 2011 Thesis 1969.1/ETD-TAMU-2011-08-9881
|h Other scheme
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| 998 |
f |
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|a 2011 Thesis 1969.1/ETD-TAMU-2011-08-9881
|t 0
|l Available Online
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