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MULTICOMPONENT INTERDIFFUSION IN AUSTENITIC NI-, FE-NI-BASE ALLOYS AND L12-NI3AL INTERMETALLIC FOR HIGH-TEMPERATURE APPLICATIONS

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Date Issued:
2009
Abstract/Description:
Interdiffusion in multicomponent-multiphase alloys is commonly encountered in many materials systems. The developments of multicomponent-multiphase alloys require control of microstructure through appropriate heat treatment, involving solid-state transformations, precipitation processes, and surface modification, where the interdiffusion processes play a major role. In addition, interdiffusion processes often control degradation and failure of these materials systems. Enhanced performance and reliable durability always requires a detailed understanding of interdiffusion. In this study, ternary and quaternary interdiffusion in Ni-Cr-X (X = Al, Si, Ge, Pd) at 900C and 700C, Fe-Ni-Cr-X (X = Si, Ge) at 900C, and Ni3Al alloyed with Ir, Ta and Re at 1200C were examined using solid-to-solid diffusion couples. Interdiffusion fluxes of individual components were calculated directly from experimental concentration profiles determined by electron probe microanalysis. Moments of interdiffusion fluxes were examined to calculate main and cross interdiffusion coefficients averaged over selected composition ranges from single diffusion couple experiments. Consistency in the magnitude and sign of ternary and quaternary interdiffusion coefficient were verified with interdiffusion coefficients determined by Boltzmann-Matano analysis that requires multiple diffusion couples with intersecting compositions. Effects of alloying additions, Al, Si, Ge and Pd, on the interdiffusion in Ni-Cr-X and Fe-Ni-Cr-X alloys were examined with respect to Cr2O3-forming ability at high temperature. Effects of Ir, Ta and Re additions on interdiffusion in Ni3Al were examined with respect to phase stability and site-preference. In addition, a numerically refined approach to determine average ternary interdiffusion coefficients were developed. Concentrations and moments of interdiffusion fluxes are employed to generate multiple combinations of multicomponent interdiffusion coefficient as a function of moments. The matrix of multicomponent interdiffusion coefficients corresponds to the lowest order of the moment. It yields real and positive eigen values which provides reliable average interdiffusion coefficients for the selected composition range.
Title: MULTICOMPONENT INTERDIFFUSION IN AUSTENITIC NI-, FE-NI-BASE ALLOYS AND L12-NI3AL INTERMETALLIC FOR HIGH-TEMPERATURE APPLICATIONS.
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Name(s): Garimella, Narayana, Author
Sohn, Yong-ho, Committee Chair
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2009
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Interdiffusion in multicomponent-multiphase alloys is commonly encountered in many materials systems. The developments of multicomponent-multiphase alloys require control of microstructure through appropriate heat treatment, involving solid-state transformations, precipitation processes, and surface modification, where the interdiffusion processes play a major role. In addition, interdiffusion processes often control degradation and failure of these materials systems. Enhanced performance and reliable durability always requires a detailed understanding of interdiffusion. In this study, ternary and quaternary interdiffusion in Ni-Cr-X (X = Al, Si, Ge, Pd) at 900C and 700C, Fe-Ni-Cr-X (X = Si, Ge) at 900C, and Ni3Al alloyed with Ir, Ta and Re at 1200C were examined using solid-to-solid diffusion couples. Interdiffusion fluxes of individual components were calculated directly from experimental concentration profiles determined by electron probe microanalysis. Moments of interdiffusion fluxes were examined to calculate main and cross interdiffusion coefficients averaged over selected composition ranges from single diffusion couple experiments. Consistency in the magnitude and sign of ternary and quaternary interdiffusion coefficient were verified with interdiffusion coefficients determined by Boltzmann-Matano analysis that requires multiple diffusion couples with intersecting compositions. Effects of alloying additions, Al, Si, Ge and Pd, on the interdiffusion in Ni-Cr-X and Fe-Ni-Cr-X alloys were examined with respect to Cr2O3-forming ability at high temperature. Effects of Ir, Ta and Re additions on interdiffusion in Ni3Al were examined with respect to phase stability and site-preference. In addition, a numerically refined approach to determine average ternary interdiffusion coefficients were developed. Concentrations and moments of interdiffusion fluxes are employed to generate multiple combinations of multicomponent interdiffusion coefficient as a function of moments. The matrix of multicomponent interdiffusion coefficients corresponds to the lowest order of the moment. It yields real and positive eigen values which provides reliable average interdiffusion coefficients for the selected composition range.
Identifier: CFE0002521 (IID), ucf:47639 (fedora)
Note(s): 2009-05-01
Ph.D.
Engineering and Computer Science, Department of Mechanical Materials and Aerospace Engineering
Doctorate
This record was generated from author submitted information.
Subject(s): Multicomponent
Interdiffusion
Austenitic
Intermetallic
High-temperature
Solid-solution
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0002521
Restrictions on Access: public
Host Institution: UCF

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