Anisotropic Fracture Behavior of Electroless deposited Ni-P Amorphous Alloy Thin Films

Abstract

ABSTRACTFracture tests have been carried out for an electroless deposited Ni-P amorphous alloy thin film with different crack growth directions. Cantilever beam type specimens with dimensions of 10 × 10 × 50 μm3 were prepared from a Ni-P amorphous thin film and notches with different directions, which are perpendicular and parallel to the deposition growth direction, were introduced by focused ion beam machining. Fatigue pre-cracks were introduced ahead of the notches. Fracture tests were performed using a mechanical testing machine for micro-sized specimens. Fracture behavior is different between the two types of specimens. As KIC values were not obtained because the criteria of plane strain were not satisfied for this size of the specimen, the provisional fracture toughness KQ values were determined. The KQ value of the specimen with crack propagation direction being perpendicular to the deposition growth direction was 4.2 MPam1/2, while that with crack propagation direction being parallel to the deposition growth direction was 7.3 MPam1/2. This result suggests that the electroless deposited Ni-P amorphous alloy thin film has anisotropic fracture properties.