β黄銅の降伏応力の異常な温度依存性

Abstract

Tensile tests were performed on β-brass at room temperature ∼500°C and at the strain rate of 4.4×10−5∼2.2×10−2 sec−1. Mechanical properties varied markedly and non-monotonously with testing temperature and strain rate as follows: With increasing temperature, the yield stress once increases and then decreases, resulting in the formation of a peak of yield stress in the range of intermediate temperature. With increasing strain rate, this peak shifts to a higher temperature and the peak value increases. The strain rate dependence of yield stress is small below the temperature of this peak, but it becomes larger above that temperature. In the temperature range where the yield stress increases anomalously with elevating temperature, that is, the range below the temperature of the peak, the yield stress changes with the strain rate in a usual manner; the greater the rate, the higher becomes the stress. On the other hand, above this temperature, the yield stress shows a normal dependence on both temperature and strain rate. Among the various strengthening mechanisms of the ordered alloys, Brown’s model seems to be most favorable to explain the pronounced anomalous temperature dependence of yield stress.