VARIATION OF MECHANICAL PROPERTIES OF IRRADIATED HASTELLOY N WITH STRAIN RATE

The postirradiation mechanical properties of several heats of Hastelloy N, both vacuum- and air-melted, have been measured after exposure to thermal fluences of 2 to 6 × 1020 neutrons/cm2. At strain rates normally encountered in tensile tests, the fracture strain is quite sensitive to strain rate in the temperature range of 500 to 650 °C. At 650 °C a minimum fracture strain was observed at a strain rate of approximately 0.1%/h; the strain increased rapidly with increasing strain rate and increased gradually with decreasing strain rate. Although the fracture strains at high strain rates differed significantly for test temperatures of 650 and 760 °C, the strains were the same under creep conditions. A titanium-modified alloy showed improved resistance to irradiation damage. Qualitative explanations are given for each of these observations. © 1969.