Measurements of local plasticity in fracture of Ni–sapphire interfaces exhibit deformation on several length scales. The deformation processes are manifest as morphology on the surface of the Ni side of the fracture surface that can be quantified with scanning probe microscopies. Four scales of deformation are observed: ligamentary bridging, crack tip blunting, slip step formation and nanometer scale roughness. The relative amount of energy dissipated in each mechanism varies with interface strength and density of precipitates. Since the most energy intensive processes, i.e. ligamentary bridging and crack tip blunting, are associated with nano precipitates, large variations in interface toughness will be related to extrinsic factors.