SUPERMODULUS EFFECT IN METALLIC SUPERLATTICES OF GRAIN-BOUNDARIES

The elastic behavior of superlattices of (100) and (111) twist grain boundaries in f.c.c. metals is investigated by means of atomistic computer simulations. The anomalous elastic and structural properties obtained from the simulations are found to be rather similar to those observed experimentally for composition-modulated strained-layer superlattices. In particular, for both plane orientations a maximum in the biaxial modulus and Young's modulus is found at about the same value of the modulation wavelength Λ (≈ 15-17 A ̊) at which a minimum appears in the modulus for shear parallel to the interfaces. A comparison of the (100) and (111) results illustrates the existence of a close connection between the elastic anomalies, the changes in sample dimensions, and the structural disorder due to-and localized at- the grain boundaries. The extremes in these moduli are shown to arise from the interaction between the interfaces. © 1990.