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Two-phase coexistence in Fe–Ni alloys synthesized by ball milling

Hong, L. B. and Fultz, B. (1996) Two-phase coexistence in Fe–Ni alloys synthesized by ball milling. Journal of Applied Physics, 79 (8). pp. 3946-3955. ISSN 0021-8979. http://resolver.caltech.edu/CaltechAUTHORS:HONjap96

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Abstract

We used mechanical alloying with a Spex 8000 mixer/mill to synthesize a series of Fe100–xNix alloys from x=0 to x=49. The Spex mill was modified so that it could also operate at a reduced milling intensity, and we compared the alloys synthesized after long times with the normal and reduced milling intensities. X-ray diffractometry and Mössbauer spectrometry were used to measure the volume fractions of the bcc and fcc phases in the alloys, and to determine the chemical compositions of the individual phases. We found that the composition ranges of the bcc and fcc single phase regions were extended well beyond their equilibrium ranges. At the higher milling intensity, we found that the bcc phase was destabilized with respect to the fcc phase, and the two-phase region shifted to lower Ni concentrations. For those alloys with coexisting bcc and fcc phases, we present evidence that the chemical compositions of the two phases are nearly the same. We explain the destabilization of the bcc with milling intensity as originating with a higher defect density in the bcc alloys than in the fcc alloys. We argue that this defect density is not homogeneous throughout the alloy, however, and the distribution of defect enthalpies can explain the two-phase coexistence in the as-milled alloys.


Item Type:Article
Additional Information:©1996 American Institute of Physics. (Received 13 November 1995; accepted 2 January 1996) We thank Professor John Morral and Dr. Hong Du for performing the Thermo-Calc calculations. This work was supported by the NSF under contract DMR-9213447.
Subject Keywords:BCC LATTICES; CHEMICAL COMPOSITION; CRYSTAL DEFECTS; ENTHALPY; FCC LATTICES; IRON ALLOYS; MECHANICAL ALLOYING; MOESSBAUER EFFECT; NICKEL ALLOYS; PHASE STUDIES; XRD
Record Number:CaltechAUTHORS:HONjap96
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:HONjap96
Alternative URL:http://dx.doi.org/10.1063/1.361821
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1806
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:18 Feb 2006
Last Modified:26 Dec 2012 08:46

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