電着ニッケル薄膜の放射光X線回折による疲労特性評価

抄録

Two types of nickel thin films with different crystal grain sizes were created by electrodeposition using a nickel sulfamate bath and fatigue crack growth tests were performed. As a result, NCG (Nano Crystalline Grain) with small crystal grain size improved mechanical properties but increased crack growth rate compared with UFG (Ultla Fine Grain) with large crystal grain size. It can be seen that a crack closure occurred in UFG because relationship between the crack growth rate and the effective stress intensity factor range shifts to the low stress intensity factor range, showing almost the same relationship as NCG. UFG showed changes in the X-ray diffraction profiles of as-received and fatigued films, but NCG showed no changes in the profiles. It is expected that plastic deformation occurred in UFG. In UFG, the compressive residual stress of fatigued films was about 10 MPa higher than that of as-received films. It can be seen that crack closure occurred in UFG because of compressive residual stress caused by plastic deformation.