4. Grain boundaries and mechanical properties of materials

We have seen (§ 4.4) that the behavior of a grain boundary upon entry of matrix dislocations – and under subsequent annealing to accommodate the resulting stresses associated with extrinsic dislocations formed – depends closely on the type of boundary: singular, vicinal or general (for naming, see § 2.4.1 in [M 4 011] ). In addition, it is profoundly modified by the presence of segregation, which can reduce the rate of diffusion (and hence dislocation ascent) and stabilize extrinsic dislocations.

To summarize, in periodic joints such as Σ = 3 {111}, Σ = 9 {221} and Σ = 11 {311} in CFC materials,...