Corrosion Fatigue Tests of Micro-Sized Specimens
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Corrosion Fatigue Tests of Micro-Sized Specimens Y. Mizutani*, Y. Higo*, Y. Ichikawa*, A. Morita*, K. Takashima*, and M.V. Swain**. *Precision and Intelligence Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan, [email protected] **Biomaterials Science Research Unit, University of Sydney, Australian Technology Park Eveleigh, NSW1490, Australia. ABSTRACT Corrosion fatigue properties of micro-sized materials are extremely important to design MEMS devices and micro-machines used in corrosive environments. However, there have been few studies that investigate corrosion fatigue properties of micro-sized materials. Thus, it is necessary to develop a corrosion fatigue test method for micro-sized materials. However, there are several difficulties in corrosion fatigue tests on micro-sized specimens. It is also necessary to clarify the problems for the method and to find their solutions. In this investigation, a corrosion fatigue test method for micro-sized specimens has been developed and corrosion fatigue tests for micro-sized Ni-P amorphous alloy specimens have been carried out in a 0.9% NaCl solution. Specimens of cantilever-beam-type with dimensions of 10 x 12 x 50 µm3 were prepared from a Ni-P amorphous thin film by focused ion beam machining. Corrosion fatigue tests on the micro-sized specimens were succeeded, and environmental effects on fatigue properties of micro-sized specimens were clearly observed. Several problems and solutions for the method were described. INTRODUCTION Micro-machines and MEMS devices are expected to be used as Bio-MEMS (diagnosis and treatment devices in human body) and inspection devices in corrosive environments. The size of components used in micro-machines and MEMS devices are considered to be on the order of microns. This size is smaller than the grain diameter in conventional metals and alloys. Mechanical properties of such micro-sized materials are considered to be different from those of bulk materials, as surface effects on the deformation mechanisms are prominent. The effect of corrosion is considered to be more prominent, because the surface area per unit volume of micro-sized specimens is larger compared with that of bulk specimens. Crevices, the size of which is also on the order of microns, may exist in micro-machines and thus crevice corrosion is also important. Therefore, corrosion fatigue properties of micro-sized materials are extremely important to design such devices. However, there have been few studies to investigate corrosion fatigue properties of micro-sized materials. This may be due to difficulties in corrosion fatigue tests on micro-sized specimens. Therefore, the objectives of this study are to develop a corrosion fatigue test method for micro-sized materials, to clarify the problems for the method and to find their solutions.
EE5.11.1
EXPERIMENTAL PROCEDURE Material The material used in this study was a Ni-11.5 wt%P amorphous alloy thin film. At present, stainless steels and titanium alloys are widely use
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