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Elastic Properties of Metallic Superlattices. Revision.
ARIZONA RESEARCH LABS TUCSON
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This Final Report describes some of the significant results from our research program on the elastic properties of metallic multilayers and superlattices. The elastic properties of composition-modulated metallic superlattice films have received considerable attention over the past fifteen years following the initial reports of anomalous enhancements of some elastic moduli as measured by the bulge tester method. For example, it was reported that the AgPd system exhibited an increase of the biaxial modulus of up to 500. However, more recent measurements failed to reproduce such large enhancements of elastic moduli in the systems for which the elastic anomaly was originally measured. The elastic anomalies observed in subsequent experiments were considerably smaller, although they showed a functional dependence on lambda with either stiffening or softening taking place in different material systems for lambda in the range of approx. 25-40 A. In apparent contrast, some Brillouin light scattering BLS measurements have shown a softening of the shear elastic constant C sub 44 in some bccfcc systems, although a stiffening was found in AuCr. Because of these apparent contradictions, coupled with the importance of this problem, we initiated a program with ONR funding to investigate these effects. In this report, we review some of our significant results obtained with ONR funding, on the structural and elastic properties observed metallic superlattice films.
APPROVED FOR PUBLIC RELEASE