The mechanical properties of nimonic alloy PE 16 are reported, for the strain-rate range 10⁻³ to 10³ s⁻¹, at ambient temperature, 400 and 500°C, on as-received, thermally aged (9864 h in sodium at 500°C), and irradiated to 9.2 dpa materials. Regarding the irradiated material one observes: (1) the effect of irradiation consisted of a marked increase of flow stress ranging between 100 and 30% and a reduction of ductility of about 20% points with respect to the as-received material; (2) decrease of flow stress with increasing strain-rate of small value at ambient temperature while it reaches the value of about 15% at high temperature; (3) dynamic strain aging with serrations along the flow curves at high temperature and low strain-rate.

The decrease of the flow stress with increasing strain-rate of the irradiated material seems to be caused by (1) the dynamic strain aging that is present at low strain rate and not at high strain rate; (2) the thermal softening caused by the temperature rise during the adiabatic dynamic testing; and (3) the accentuation of the effects of the two preceeding phenomena caused by the damage introduced by irradiation.