Toshihiro Yano, Xu Ling,Tatsuo Yokote and Ryuuta Onodera
Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 812-0053
In order to examine the effect of grain boundary sliding on fracture in leaded alpha brass during hot working, hot compression tests with the strain rate of 0.1-0.4 s-1 were carried out at 973 K for Cu-35 mass%Zn including 0-1.5 mass% lead using specimens with three different grain sizes ranging from about 50 to about 200 μm in diameter. In addition, the effectiveness of changing the surface phase for improving poor formability in leaded alpha brass was shown. The results were as follows:
(1) The fracture was influenced by lead content and grain size. In non-leaded alpha brass, fracture did not occur at any grain size. In leaded alpha brass containing 0.5-1.5 mass% lead, the fracture occurred easier with an increase in grain size (>100 μm).
(2) The fracture occureed only at the free surface and was attributed to the grain boundary sliding.
(3) The grain boundary slid more easily as the grain size increased. The amount of sliding was increased by the existence of lead particles. The behavior of grain boundary sliding corresponded to the fracture behavior of leaded alpha brass during hot working.
(4) The poor formability of leaded alpha brass was remarkably improved by changing the phase of the specimen surface from alpha to beta. This result suggests that the alpha grain boundary slides more easily than the beta grain boundary essentially.
(Received July 7, 1998; In Final Form September 11, 1998)
fracture, hot working, compression, alpha brass, lead, grain size, grain boundary sliding, free surface
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