Microstructural design of high-strength aluminum alloys

A summary is presented of recent attempts to model the effects of precipitate shape, orientation, and distribution on yield strength and age-hardening response, using appropriate versions of the Orowan equation and models of precipitation strengthening developed for Al alloys containing a single uniform distribution of rationally oriented plate- or rod-shaped precipitates, which are either shearable or shear resistant. It is demonstrated that these models of particle strengthening are capable of predictions that are in excellent quantitative agreement with experimental observations that high tensile yield strength is associated with microstructures containing a high density of intrinsically strong, plate-shaped precipitates with {111}_α or {100}_α habit planes and large aspect ratio. The authors predict that further improvement in the strength of existing Al alloys might be achieved by increasing the number density and/or aspect ratio of rationally oriented precipitate plates.