Solidification of a heterogeneous Multiphase Laves-based Hydrogen Storage Alloy

Published

August 15, 2010

Author(s)

William J. Boettinger, Dale E. Newbury, Ke Wang, Leonid A. Bendersky, Chun Chiu, Ursula R. Kattner, K. Young, B. Chao

Abstract

The solidification microstructure of a nine-element Zr-Ni based AB(sub 2) type C14/C15 Laves hydrogen storage alloy is determined. The selected composition represents a class of alloys being examined for usage as a metal hydride electrode in nickel metal-hydride batteries. These alloys often have their best properties in the cast state. Solidification is accomplished by: dendritic growth of a hexagonal C14 Laves phase; peritectic solidification of a cubic C15 Laves phase and formation of a cubic B2 phase in the interdendfritic regions. The B2 phase decomposes in the solid state into a complex multivariate plate-like structure containing ZrNi-rich intermetallics. The closeness of the compositions of the C14 and C15 phases required the use of state of the art compositional mapping with an energy dispersive detector capable of processing a high x-ray flux to locate regions for quantitative composition measurement and TEM examination. Liquid composition paths and their associated solid phase formation sequences are computed in the constituent ternary subsystems of the Ni-Cr-Ti-Zr quaternary phase diagram. Comparison with the experimentally determined paths shows promise but also indicates the need for quaternary and high order thermodynamic assessments.

Citation

ACTA Materialia

Pub Type

Journals

Keywords

Phase diagram, Sodification, Hydrogen storage, Microprobe analysis

Citation

Boettinger, W. , Newbury, D. , Wang, K. , Bendersky, L. , Chiu, C. , Kattner, U. , Young, K. and Chao, B. (2010), Solidification of a heterogeneous Multiphase Laves-based Hydrogen Storage Alloy, ACTA Materialia (Accessed December 6, 2024)