Strengthening via Orowan Looping of Misfitting Plate-like Precipitates

Many common engineering alloys are strengthened by precipitates with plate-like geometries. The mechanics of precipitation strengthening, while well resolved with spherical precipitates, are less well understood for plate-like geometries. In this work, we employ discrete dislocation dynamics simulations to study precipitation strengthening by θ′ precipitates in AlCu. We show that Orowan looping with parallel plate-like precipitates can be fundamentally different from spheres because it is governed by a steady-state glide process rather than a single critical dislocation geometry. We develop a model based on the formation of a dislocation dipole across the precipitate thickness to explain the observed strengthening. Finally, we show that while the precipitate misfit field can lead to both strengthening and weakening, strengthening is more common because of the steady-state process by which Orowan loops form.