A summary is presented of recent attempts to model the effects of precipita
te 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 uni
form distribution of rationally oriented plate- or rod-shaped precipitates,
which are either shearable or shear resistant. It is demonstrated that the
se models of particle strengthening are capable of predictions that are in
excellent quantitative agreement with experimental observations that high t
ensile yield strength is associated with microstructures containing a high
density of intrinsically strong, plate-shaped precipitates with {111}(alpha
) or {100}(alpha) habit planes and large aspect ratio. The authors predict
that further improvement in the strength of existing Al alloys might be ach
ieved by increasing the number density and/or aspect ratio of rationally or
iented precipitate plates.