INTERGRANULAR FRACTURE DURING POWER-LAW CREEP

The growth of an array of grain boundary voids during creep deformation is analysed. Growth by power-law creep alone is modelled first, and it is shown that this cannot completely explain the observed times (tf{hook}) or strains (ε{lunate}f{hook}) to fracture. Growth by coupled diffusion and power-law creep is then modelled: each void grows by diffusion, but the void plus its diffusion dfield is contained within a cage of power-law creeping material. The model leads to simple equations for tf{hook}, and ε{lunate}f{hook} and allows the range of stress, strain-rate and temperature in which this coupled mechanism is important to be defined. The model is closely related to, and extends, that of Beere and Speight [1]. It is compared with this work and that of Pavinich and Raj [2]. © 1979.