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Title: The Role of Phase Stability in Ductile, Ordered B2 Intermetallics

Abstract

We discuss the underlying atomistic mechanism for experimentally observed large tensile ductility in various strongly ordered B2 intermetallic compounds. First-principles calculations demonstrate that all of the compounds exhibit little energy differences between the B2, B27 and B33 phases. These calculations relate observations of ductility in YAg, YCu and ZrCo to shape-memory materials including NiTi. One transformation pathway between the B2 and B33 phases establishes a connection between this phase competition, and stacking faults on the {l_brace}011{r_brace}B2 plane. The low energy of such a stacking fault will lead to splitting of the b=<100> dislocations into b/2 partials, observed in ZrCo, TiCo, and in the B19' phase of NiTi. Calculations demonstrate that this pathway is competitive with the traditional pathway for NiTi.

Authors:
 [1];  [2];  [1];  [1]
  1. ORNL
  2. Ames Laboratory and Iowa State University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931832
DOE Contract Number:
AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Journal Volume: 980; Conference: 2006 MRS Fall Meeting, Boston, MA, USA, 20061127, 20061201
Country of Publication:
United States
Language:
English

Citation Formats

Morris, James R, Ye, Y. Y., Krcmar, Maja, and Fu, Chong Long. The Role of Phase Stability in Ductile, Ordered B2 Intermetallics. United States: N. p., 2007. Web. doi:10.1557/PROC-980-0980-II06-10.
Morris, James R, Ye, Y. Y., Krcmar, Maja, & Fu, Chong Long. The Role of Phase Stability in Ductile, Ordered B2 Intermetallics. United States. doi:10.1557/PROC-980-0980-II06-10.
Morris, James R, Ye, Y. Y., Krcmar, Maja, and Fu, Chong Long. Mon . "The Role of Phase Stability in Ductile, Ordered B2 Intermetallics". United States. doi:10.1557/PROC-980-0980-II06-10.
@article{osti_931832,
title = {The Role of Phase Stability in Ductile, Ordered B2 Intermetallics},
author = {Morris, James R and Ye, Y. Y. and Krcmar, Maja and Fu, Chong Long},
abstractNote = {We discuss the underlying atomistic mechanism for experimentally observed large tensile ductility in various strongly ordered B2 intermetallic compounds. First-principles calculations demonstrate that all of the compounds exhibit little energy differences between the B2, B27 and B33 phases. These calculations relate observations of ductility in YAg, YCu and ZrCo to shape-memory materials including NiTi. One transformation pathway between the B2 and B33 phases establishes a connection between this phase competition, and stacking faults on the {l_brace}011{r_brace}B2 plane. The low energy of such a stacking fault will lead to splitting of the b=<100> dislocations into b/2 partials, observed in ZrCo, TiCo, and in the B19' phase of NiTi. Calculations demonstrate that this pathway is competitive with the traditional pathway for NiTi.},
doi = {10.1557/PROC-980-0980-II06-10},
journal = {},
number = ,
volume = 980,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • Recent research on phase stability and grain boundary structure in ordered intermetallics is summarized. Ordered intermetallics have many attractive high-temperature properties;however, low ductility and brittle fracture limit their use for structural applications. Embrittlement in intermetallics is mainly caused by low-crystal symmetry and insufficient number of slip systems, poor cleavage strength, and intrinsic and extrinsic grain-boundary weakness. Experimental studies of ordered phase stability and grain-boundary structure have led to substantial improvement in the ductility and fracture toughness of several ordered intermetallics, including (Co,Fe)/sub 3/V, (Ni,Fe)/sub 3/V, (Co,Ni,Fe)/sub 3/V, Fe/sub 3/Al, Ni/sub 3/Al, Ni/sub 3/Ga, and Ni/sub 3/Si. At present, the controlmore » of ordered structures and grain-boundary properties is mainly based on some empirical andor phenomenological relationship. First-principles calculations have advanced to the stage that they are able to help us to understand the electron structure and phase stability and to design ductile ordered intermetallic alloys for structural use at elevated temperatures. 64 refs., 11 figs., 1 tab« less
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