アルミニウム粗大結晶の疲労強度

概要

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The fatigue test has been carried out on coarse grained aluminum at the conditions of ambient pressure and 6×10^<-5> Torr, in order to investigate the effect of atmospheric-corrosion on the fatigue strength of aluminum. Furthermore, to understand the difference of fracture modes at these two environmental conditions, the external and fracture surfaces were observed by means of optical and scanning electron microscopies. The results were discussed from the view point of grain size dependence. The main results obtained were as follows : (1) The fatigue strength of aluminum in vacuum was higher than that in air. The fatigue resistance of a specimen decreased with increasing the grain size. However, the effect of grain size was not so much when the applied stress level was low. (2) The fatigue test on single crystal showed that the effect of atmospheric-corrosion on the fatigue process is different for each crystal. The fatigue behavior of a single crystal in vacuum is considered to be purely dependent upon the crystallographic matters. (3) Many cracks of trans-granular type are observed in the specimens tested in vacuum, while those of inter-granular type exist in the specimens tested in air. Also, there are striations on the fracture surface of the specimens tested in air, but not in vacuum.
1975-01-15