Study of the recrystallisation of aluminium/alumina (SAP) alloys
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The influence of the introduction of aluminium nuclei on the recrystallisation behaviour of SAP (sintered aluminium powder) was studied by metallographic observations using a new etching reagent, and by transmission electron microscopy. It was observed that the artificial nuclei can grow in the SAP matrix only in the temperature range in which the alloy recrystallises spontaneously. It is concluded that the physical process inhibited by the dispersed particles is grain-boundary migration.
These results and those previously reported confirm Cahn's theory (which regards the formation of new grains as due to recovery phenomena localised in the regions of highest lattice distortion) supplemented by the coalescence mechanism proposed by Hu and Li, Moreover, the basic concepts of “nucleation” and “growth” currently employed to describe recrystallisation phenomena are critically discussed: it is concluded that a reformulation of these concepts is necessary on the basis of the information obtained by means of the more recent experimental techniques, such as electron microscopy.
KeywordsTransmission Electron Microscopy Recrystallization Disperse Particle Basic Concept Lattice Distortion
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