日本金属学会誌

J. Japan Inst. Metals, Vol. 39, No. 3 (1975),
pp. 298-305

The Directionality of Fatigue Behavior of Cold-Rolled Copper

Masao Uemura1, Kiyoshi Kigawa2, Hideaki Kawabe1 and Tomoharu Yamada1

1Department of Precision Engineering, Faculty of Engineering, Osaka University, Suita
2Graduate School, Osaka University, Suita. Present address: Sumitomo Light Metals Ind. Ltd., Nagoya

Abstract:

To clarify the factor governing the directionality of fatigue behavior of 90% cold-rolled tough pitch copper, the surface structures are observed through optical and replica electron microscopy, and the fatigue phenomenon is discussed taking the 111 pole figure into consideration.
The following results are obtained:
(1) In the higher stress amplitude region with respect to the fatigue life about 106 cycles, the fatigue life of a test piece taken in the transverse direction to the rolling direction is longer than in the parallel direction. On the other hand, in the lower stress amplitude region the latter has a longer fatigue life than the former.
Due to the difference in fatigue lives, the structure of slip bands changes from coarse slip bands in the higher stress amplitude region to island-like slip bands in the lower stress amplitude region.
(2) In the higher stress amplitude region, the fatigue crack emerges as the slip band crack along the coarse slip band. In the lower stress amplitude region, however, fatigue crack emerges in the island-like slip band in the similar process as in the annealed specimen.
(3) Directions of the coarse slip band and the slip band crack correspond very well with those predicted from the 111 pole figure of rolled copper. Thus the directionality in the fatigue behavior in the higher stress amplitude region can be explained qualitatively from the 111 pole figure of the rolled specimen.
(4) On the other hand, in the island-like slip band very fine slip bands emerge in the direction predictable from the cube texture, so that in the process of crack emergence the directionality is not found. In this case the directionality of the fatigue strength can be explained mainly by the shape of grains elongated by rolling.


(Received 1974/09/17)

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