Microstructural studies of multiphase (Zr,Ti)(V,Cr,Mn,Co,Ni)2 alloys for NiMH negative electrodes

L. A. Bendersky, K. Wang, W. J. Boettinger, D. E. Newbury, K. Young, B. Chao

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations

Abstract

The solidification microstructures of six Laves-based (Zr,Ti)(TM,Ni) 2 alloys (TM= V,Cr, Mn,Co) intended for use as novel negative electrodes in Ni-metal hydride batteries were studied here; these alloys often have their best electrochemical properties when in the cast state. Solidification occurs by dendritic growth of a hexagonal C14 Laves phase followed by peritectic solidification of a cubic C15 Laves phase and formation of a cubic B2 phase in interdendritic regions. The observed sequence of Laves phase C14/C15 upon solidification agrees with predictions using effective compositions and thermodynamic assessments of the ternary systems, Ni-Cr-Zr and Cr-Ti-Zr. The paper also examines the complex internal structure of the interdendritic grains formed by solid-state transformation, which plays an important role in the electrochemical charge/discharge characteristics. By studying one alloy it is shown that the interdendritic grains solidify as a B2 (Ti,Zr)44(Ni,TM)56 phase, and then undergo transformation to Zr7Ni10-type, Zr9Ni11-type and martensitic phases. The transformations obey orientation relationships between the high-temperature B2 phase and the low-temperature Zr-Ni-type intermetallics, and consequently lead to a multivariant structure. Binary Ni-Zr and ternary Ti-Ni-Zr phase diagrams were used to rationalize the formation of the observed domain structure.

Original languageEnglish (US)
Title of host publicationIntermetallic-Based Alloys for Structural and Functional Applications
Pages329-334
Number of pages6
DOIs
StatePublished - 2011
Event2010 MRS Fall Meeting - Boston, MA, United States
Duration: Nov 29 2010Dec 3 2010

Publication series

NameMaterials Research Society Symposium Proceedings
Volume1295
ISSN (Print)0272-9172

Other

Other2010 MRS Fall Meeting
CountryUnited States
CityBoston, MA
Period11/29/1012/3/10

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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