Cu-6.0wt%Al合金の中応力繰返し曲げ疲労に関するき裂の進展

抄録

In a previous paper, it was reported that various changes in structure and in hardness of Cu-6.0wt% Al alloy at different stages of repeated bending fatigue test were studied by hardness test and by both micro-and electron microscopic observation. In the present report, the author observed the changes of behaviour that appeared during the process to the final rupture in the above-mentioned fatigue tests, employing various kinds of measuring apparatuses, micro-and electron microscopes, hardness tester, internal friction tester and X-ray analyser.
The experimental results are summarized as follows:
(1) The initial formation of slip lines are observed during the first stress cycling, and they are all a type of homogeneous slip lines.
(2) After the homogeneous slip lines, rippling phenomena of slip lines are observed. After the rippling phenomena, the intrusion and extrusion are observed.
(3) After the intrusion and extrusion, the very large intrusion and extrusion change gradually to micro-cracks.
(4) The hardness of the specimens increases with increase in stress cycling numbers and the maximum hardness is obtained around the fractured area.
(5) The internal friction increases until 1×10³ cycling numbers and after it decreases with increase in stress cycling numbers and 1×10⁴ cycling numbers there is a large decrease in the internal friction. Then, the internal friction increases with increasing stress cycling numbers.
(6) The X-ray diffraction pattern changes with increase in stress cycling numbers and the Laue spots above the Debye rings exhibit the phenomena of extensibility.