The effect of irradiation on the fatigue and flow behavior of TZM alloy

Abstract The pre- and postirradiation fatigue and flow properties of the molybdenum-base alloy TZM have been determined at 427°C. Neutron irradiation to a fluence of 1 × 10 22 n/cm 2 > 0.1 MeV increased the fatigue life of the stress relieved alloy in vacuum by approximately a factor of two in the strain range of 0.11 to 0.18%. The environmental effect of gaseous impurities on the rate of fatigue crack growth in unirradiated TZM was investigated for air pressures from approximately 10−4 to 100 Pa. Compressive now properties were determined at 427°C at a strain rate of 1 × 10−3 sec−1 and at 500°C for a range of strain rates. Irradiation to a fluence of 1.2 × 1022 n/cm2 increased the yield strength of stress relieved TZM by about 50 percent. The ductile to brittle transition temperature appeared to be between 427 and 500°C at a compressive strain rate of 1 × 10−3 sec−1. Irradiation induced changes in microhardness and yield strength were correlated with TEM results using general hardening models.