Fatigue Tests of Ni–P Amorphous Alloy Microcantilever Beams

Abstract

Fatigue life and fatigue crack propagation tests have been performed on microsized Ni-P amorphous alloy specimens to investigate the fatigue properties of this material. The material used was a Ni-11.5 wt%P amorphous thin film. The specimens tested were cantilever-beam-type specimen with dimensions of 30 × 12 × 50 µm 3 prepared by focused ion beam machining. Notches with a depth of 3 µm were introduced in some specimens. The entire set of fatigue tests was performed using a newly developed fatigue testing machine in air at room temperature under a constant load ratio of 0.1. The fatigue life curve was obtained for unnotched specimens, and the fatigue strength of the specimen was determined to be approximately one-third of the static bending strength. Fatigue crack propagation tests were performed using notched specimens. Fine equispaced markings were observed on the fatigue surface. These markings are aligned perpendicular to the crack growth direction, and are considered to be striations. Therefore, even in microsized amorphous alloys the crack is deduced to propagate by cyclic plastic deformation at the crack tip.

Experimental methods for the characterization of fatigue in microstructures

“…Some examples are listed in the following: uniaxial cyclic loading tests were performed on single crystal specimens and a reduction in fatigue life was observed for specific strain levels [8]. The fracture caused by fatigue loading on Ni-P amorphous alloy microcantilevers was studied and the fatigue strength resulted about one-third of the static bending strength [9]. From the aspect of fracture striations the authors concluded that the crack propagation occurs by cyclic plastic deformation at the crack tip.…”

Statistical Fatigue Property of Multi-Layer Amorphous Metal Composites in Axial Loading

“…In the case of actual use of amorphous metals for mechanical components, their mechanical properties should be evaluated as fundamental design data. Thus, the mechanical properties of amorphous metals have been investigated by many researchers in recent years [7][8][9]. However, the most important property for the actual machine design is fatigue strength of the structural materials, since every product should endure during a definite period without failure under cyclic loadings.…”

In Situ SEM Torsion Test of Metallic Glass Microwires Based on Micro Robotic Manipulation

“…Although there have been extensive studies on the mechanical behavior of microwire materials in the past two decades, such as static tensile test [ 24 – 27 ], micro/nanoindentation measurement [ 28 – 30 ], bending measurement [ 31 – 33 ], and dynamic resonance frequency fatigue test [ 34 , 35 ], little was reported on the behavior of microwire under the torsional loading [ 36 – 38 ]. Torsion of thin wires is a fundamental and excellent approach to explore the mechanical behavior, from elastic deformation, through yielding, to the strain-hardening regime.…”