9. The role of intergranular diffusion in superplastic creep processes

Almost all material behaviors depend on their diffusional properties: phase changes, corrosion, mechanical strength at high temperatures [M 55] . Depending on the conditions of use, they involve volume diffusion, coupled or not with intergranular diffusion.

The latter is particularly active in explaining the enormous creep ductility of fine-grained materials (i.e. with a high volume proportion of grain boundaries) identified as superplastic behavior. This ductility can lead to elongations of the order of 1,000 to 2,000% (i.e. twenty times the initial length) in metals, for grain sizes...