32.Threshold Stress for High-Temperature Deformation of Dispersion-Strengthened Alloys

In order to identify the mechanism originating the threshold stress for the high-temperature deformation of dispersion-strengthened alloys, stress-change tests were conducted during deformation of an Al-1.5 vol%Be alloy. It was found that the instantaneous strain on the increase in applied stress was absolutely elastic when the stress-increment was below a certain value an instantaneous plastic strain was observed for whereas the strain was always elastic for a stress-decrement. The critical stress depended on temperature and showed a maximum in a temperature range from 570 K to 620 K. From these findings it is discussed that the threshold stress should be determined by the Srolovitz mechanism.