Summary Dislocations can interact with the stress fields of precipitates. Moving dislocations can: 1.glide through coherent precipitates->shearing the precipitate. 2.bow around incoherent precipitates,leaving loops as they bypass two precipitates which act like pinning centres for the dislocations leading to an increase in the dislocation density). Both these processes need an application of higher stresses (assuming an harder precipitate)lead to the strengthening of the material. ▣ Semi-coherent precipitates have interfacial misfit dislocations which partially relieve the coherency strains.(These dislocations are structural dislocations). 轨Summary 4 q Dislocations can interact with the stress fields of precipitates. q Moving dislocations can: 1. glide through coherent precipitates → shearing the precipitate. 2. bow around incoherent precipitates, leaving loops as they bypass two precipitates which act like pinning centres for the dislocations (→ leading to an increase in the dislocation density). q Both these processes need an application of higher stresses (assuming an harder precipitate) → lead to the strengthening of the material. q Semi-coherent precipitates have interfacial misfit dislocations which partially relieve the coherency strains. (These dislocations are structural dislocations)