Hydrogen influence on mechanical and fracture mechanics characteristics of zirconium Zr-2.5Nb alloy at ambient and elevated temperatures

This article deals with the investigation of the hydrogen concentration and temperature influence onto mechanical and fracture mechanics characteristics of RBMK-1500 Ignalina NPP unit 2 reactor fuel channel material-Zr-2.5Nb zirconium alloy (TMT-2) at temperatures from ambient up to 300 deg. C. The investigation of mechanical characteristics was performed on tensile specimens, fracture mechanics characteristics KQ, KC*, JIC-on compact specimens (B = 4 mm) of hydrogen-free and saturated by hydrogen (52, 100 and 140 ppm) at 20, 170, 200 and 300 deg. C. The investigation showed that temperature increasing calls mechanical strength decreasing, whereas the reductions of area increase. Stronger influence of hydrogen concentration onto mechanical characteristics is noticed only at 20-170 deg. C temperature, however this influence diminishes as the temperature increases and weakest hydrogen influence is given at 300 deg. C. Fracture toughness characteristics KQ, KC* more depends on temperature than on hydrogen concentration. Critical JIC integral values for the specimens containing hydrogen were given lowest at 20 deg. C, increases when temperature were raised up to 140 deg. C and were given highest when it reaches 300 deg. C. The analysis of KC* and JIC dependence due to the mechanical characteristics of zirconium alloy has showed that the modified plasticity Zmod = (Rp0.2/Rm)Z satisfactorily approximates the influence of temperature and hydrogen concentration on variation of these characteristics