  Alloying metals with other elements is often done to improve the material
strength or hardness. A key microscopic mechanism is precipitation hardening,
where precipitates impede dislocation motion, but the role of such obstacles in
determining the nature of collective dislocation dynamics remains to be
understood. Here, three-dimensional discrete dislocation dynamics simulations
of FCC single crystals are performed with fully coherent spherical precipitates
from zero precipitate density upto $\rho_p = 10^{21}\,\text{m}^{-3}$ and at
various dislocation-precipitate interaction strengths. When the
dislocation-precipitate interactions do not play a major role the yielding is
qualitatively as for pure crystals, i.e., dominated by "dislocation jamming",
resulting in glassy dislocation dynamics exhibiting critical features at any
stress value. We demonstrate that increasing the precipitate density and/or the
dislocation-precipitate interaction strength creates a true yield or
dislocation assembly depinning transition, with a critical yield stress. This
is clearly visible in the statistics of dislocation avalanches observed when
quasistatically ramping up the external stress, and is also manifested in the
response of the system to constant applied stresses. The scaling of the
yielding with precipitates is discussed in terms of the Bacon-Kocks-Scattergood
relation.
