Nanoindentation has been applied to quantitative characterization of interfaces of bonded materials. Distributions of indentation hardness and Young's modulus on material surface are precisely determined using a load-controlled nanoindentation tester. Two kinds of coatings, a diffusion bonding of aluminum alloy and stainless steel and a spot welding of carbon steels, are used for specimens. It has been found for the diffusion bonding that the intermetallic compound layer of 4μm produced at the interface has higher mechanical properties than the base materials. Twodimensional mapping of mechanical properties on the cross section of the spot welding has successfully been performed. It has been observed that the properties of the welding area are significantly different from the base material.
