Elastic moduli of polycrystalline LaAl xNi 5-x

M. Bereznitsky, A. Ode, J. E. Hightower, O. Yeheskel, I. Jacob, R. G. Leisure

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

A hot isostatic pressing technique was used to prepare bulk polycrystalline samples of the hydrogen-absorbing materials LaAl xNi 5-x. Ultrasonic methods were used to measure the elastic moduli of these alloys. Small corrections were made for porosity so that values expected for the theoretical density were found. The various moduli decrease somewhat with increasing x; the porosity-corrected bulk and shear moduli are 137.4 GPa and 59.2 GPa, respectively, at x=0 and decrease to 126.6 GPa and 54.1 GPa, respectively, at x=1. Poisson's ratio is independent of x within experimental error at 0.31, a value typical for metals. Debye temperatures calculated from the porosity-corrected elastic constants ranged from 360 to 365 K, and were in good agreement with those reported from heat capacity measurements. The present measurements on LaAl xNi 5-x were combined with earlier heat capacity measurements of the hydrides, LaAl xNi 5-xH y, to estimate the elastic moduli of the latter materials. The estimated hydride moduli were substantially lower than those of the hydrogen-free metal. These estimated moduli were used to calculate the elastic energy associated with coherent, ellipsoidal hydride precipitates. The minimum elastic energy was found for low aspect ratio, i.e., a plate as opposed to a sphere or needle.

Original languageEnglish
Pages (from-to)5010-5015
Number of pages6
JournalJournal of Applied Physics
Volume91
Issue number8
DOIs
StatePublished - 15 Apr 2002

ASJC Scopus subject areas

  • Physics and Astronomy (all)

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