Enhanced elastic modulus in composition-modulated gold-nickel and copper-palladium foils

The biaxial elastic modulus Y[111] has been measured by bulge testing in Au-Ni and Cu-Pd foils containing short-wavelength one-dimensional composition modulations produced by vapor deposition. As compared with homogeneous foils of the same average composition, the modulated foils exhibited an appreciable increase in modulus - from 0.21 to 0.46 TPa for Au-Ni and from 0.27 to 1.31 TPa for Cu-Pd. For the latter system, the increase was found to be proportional to the square of the amplitude of the modulation. The enhancement of the modulus decreased with increasing wavelength and for wavelengths greater than 3 nm the modulus was the same as that for homogeneous foils. It was also observed that the deformation was non-Hookian; the slope of the stress-strain curves decreased with increasing strain.