Investigations of the effect of creep fatigue interaction in a Cu-Cr-Zr alloy

The low cycle fatigue, the creep and the creep-fatigue properties of Cu-Cr-Zr have been investigated at 300 °C. The material investigated is an ELBRODUR G, heat treated to the following condition: 980°C-30 min, ageing 580°C-2 hours. This condition corresponds to a possible fabrication and heat treatment route of the first wall blanket panels of the ITER fusion reactor. The microstructure is characterized by a coarse grain size, with grains reaching sizes up to 500 μm. Curves and equations describing the creep and the fatigue properties have been obtained. A few creep-fatigue experiments have been conducted for tensile dwells of 30 and 300 sec. The results have been analyzed according to the time based life assessment method. The results indicate that fatigue and creep damage are not simply additive but a strong interaction takes place, especially at low imposed strains. The life reduction is due to the incompatibility of the deformation mechanisms taking place under fatigue and creep loading. Two damage envelopes for 30 and 300 sec have been determined. They can be used for making predictions between close experimental points.