Elastic modulus in composition-modulated silver-palladium and copper-gold foils

Abstract
The biaxial elastic modulus Y[111] has been measured by bulge testing in Ag-Pd and Cu-Au thin foils containing one-dimensional composition modulations with wavelengths ranging from 0.9 to 5.5 nm. For the Ag-Pd foils having wavelengths of 2.0–3.0 nm, the modulus was up to 2.3 times greater than that of homogeneous foils of the same average composition. The increase was found to be proportional to the square of the amplitude of the modulation. In foils containing modulations of wavelengths less than 2.0 nm or greater than 3.0 nm, the modulus was the same as that of homogeneous foils. It was observed that the deformation was elastic but non-Hookean. For the Cu-Au modulated foils no modulus enhancement was observed: The modulus for any wavelength was in good agreement with that calculated from the bulk elastic constants.