Fracture of leaded alpha brass during hot working and improvement of its formability

In order to examine the effect of grain boundary sliding on fracture in lea ded alpha brass during hot working, hot compression tests with the strain r ate 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 mu m in diameter. In addition, the effectivenes s of changing the surface phase for improving poor formability in leaded al pha brass was shown. The results were as follows: (1) The fracture was influenced by lead content and grain size. In non-lead ed alpha brass, fracture did not occur at any grain size. In leaded alpha b rass containing 0.5-1.5 mass % lead, the fracture occurred easier with an i ncrease in grain size (>100 mu m) (2) The fracture occureed only at the free surface and was attributed to th e grain boundary sliding. (3) The grain boundary slid more easily as the grain size increased. The am ount of sliding was increased by the existence of lead particles. The behav ior of grain boundary sliding corresponded to the fracture behavior of lead ed alpha brass during hot working. (4) The poor formability of leaded alpha brass was remarkably improved by c hanging the phase of the specimen surface from alpha to beta. This result s uggests that the alpha grain boundary slides more easily than the beta grai n boundary essentially.