Abstract
For a further understanding of high temperature tensile-deformation behavior of a Cu-30 mass% Zn binary alloy depending on the strain rate, the structure and the stress-strain curves were investigated in detail, at 673 K, using a salt bath (NaNO3: KNO3=1: 1) under a strain rate range from 3.3×10-5 to 2.0×10-1s-1. Specimens with three grain sizes ranging from 0.012 to 0.045 mm diameter were used. When dynamic recrystallization occurred at 673 K, the stress decreased. After the initial grain shape changed to dynamic recrystallization, the stress-strain curves showed a steady state, and did not depend on the occurrence or the growth of voids. The peak strain, which is the strain at maximum stress, was hardly dependent on the size of the initial grain, but dependent on the strain rate. Thus, the peak strain increases with strain rate. At this time, the dynamic recrystallization form is a bulging mechanism and simultaneously, a nucleation mechanism. This occurrence happened at about 20-30% peak strain. Initial void formation depended on the strain rate. And the strain appearing void increased with increased in strain rate. Cavities of fractured specimens showed 4 different shapes in three dimensions which corresponded to initial grain size and strain rate. Fractured elongation reveals a tendency to become smaller, when cavities start to combine and grow into a 45 degree angle in relate to the tensile direction. On the other hand, the specimens exhibit large elongation, when cavities combine and grow in the tensile direction.
