The hardness and modulus of molybdenum silicide/niobium microlaminates and stressed materials determined by nanoindentation

Nanoindentation techniques have been used to explore the hardness and elastic modulus of Nb/MoSi$\sb2$ microlaminates and stressed aluminium and stainless steel alloys. The elastic moduli of the microlaminates fall on the high end of range set by the rule-of-mixtures and increase slightly above it at small wavelengths. The hardness of the microlaminates increases with decreasing wavelength in a manner consistent with Hall-Petch strengthening. It is shown that average mechanical properties of the microlaminates can be measured when the plastic penetration depths are as small as one bilayer thickness. Studies in the aluminium alloy and stainless steel show that while hardness is affected by applied stress, the standard methods by which hardness and modulus are determined from nanoindentation data may lead to inaccuracies when large stresses exist in the material