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Deshpande, Anirudha Rajendra (2006) ANNEALING BEHAVIOR OF HEAVILY COLD DEFORMED, EQUIATOMIC, FERROMAGNETIC Fe-Pd INTERMETALLICS. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Reversibly ordering Fe-Pd intermetallics for equiatomic composition exhibit high temperature stable, disordered FCC phase and low temperature (< Tc) stable L1₀-ordered phase. In this system FCC to L1₀ ordering phase transformation has been associated with development of lamellar microstructural morphology known as 'polytwin' microstructure. Previously polytwin microstructure has been replaced by equiaxed grained morphology of L1₀-ordered phase that exhibits enhanced magnetic properties. A combined reaction (CR) of FCC to L1₀ ordering phase transformation concomitant with annealing of defects introduced in metastable FCC phase has been utilized to attain equiaxed grained L1₀-ordered microstructure. Such CR have also been utilized in other systems that undergo an ordering phase transformation. With exception of some studies, most of these prior investigations have utilized framework of conventional annealing (recovery, recrystallization and grain growth) that has been developed for disordered dilute solid solutions that do not undergo an ordering phase transformation (e.g. annealing of Cu), to understand evolution of microstructure during CR. A clear distinction between conventional annealing (cold deformation of ordered alloy followed by recovery, recrystallization and grain growth in ordered deformed matrix) and combined reaction (an ordering phase transformation concomitant with annealing of defects introduced in disordered parent phase) has not been realized. Creation of a clear distinction between both of these modes of transformation in model Fe-Pd system is the main motivation of this study. Disordered FCC parent phase (prior to CR) and L1₀-ordered phase (prior to conventional annealing) have been deformed by cold rolling to comparable % reduction in thickness. Both of these annealing transformations have been conducted at same temperature. The microstructural mechanisms that lead to generation of equiaxed grained microstructures of L1₀-ordered phase in both of these transformations have been investigated. Vital differences in these transformations such as prior cold deformed state, texture evolution during transformation, kinetics of transformation etc. have been recognized. Similarities in these transformations such as mechanisms for crystal defects formation, texture evolution during grain growth have also been identified. Existing theories and modifications thereof have been used to rationalize observed similarities and differences between both of these modes of transformation.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Deshpande, Anirudha Rajendraard24@pitt.eduARD24
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairWiezorek, Jorg M.Kwiezorek@pitt.eduWIEZOREK
Committee MemberLaughlin, David
Committee MemberBarnard, John AJBarnard@engr.pitt.eduJBARNARD
Committee MemberYang, Judith CJYang@engr.pitt.eduJUDYYANG
Committee MemberMao, Scottsmao@engr.pitt.eduSXM2
Committee MemberKlemmer, Timothy
Date: 1 February 2006
Date Type: Completion
Defense Date: 20 October 2005
Approval Date: 1 February 2006
Submission Date: 29 October 2005
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Materials Science and Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: annealing behavior; combined reactions; crystallogrpahic texture; electron microscopy; Fe-Pd; ferromagnetic intermetallics; L1₀-ordered; X-ray diffraction
Other ID:, etd-10292005-101954
Date Deposited: 10 Nov 2011 20:03
Last Modified: 15 Nov 2016 13:51


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