Precipitation hardening was investigated by performing computer simulations of dislocations gliding through a matrix containing spherical coherent precipitates, and deducing the critical resolved shear stress. The radius distribution, and the 3-dimensional spatial arrangement of the particles, were chosen so as to be close to those of a real Ostwald-ripened crystal. The precipitates were assumed to be long-range ordered, unlike the surrounding matrix. A dislocation which cut through them generated an antiphase boundary and thus sensed an obstacle stress, within the precipitates, which impeded dislocation glide. Such a strengthening mechanism operated in the Ni-based superalloy, Nimonic PE16. The simulations were based upon the local stress equilibrium along the dislocation line. The linear elastic interaction of the dislocations with themselves and with other dislocations was fully allowed for. Over-aged crystals were considered, in which dislocation glide was governed by the Orowan process. The strengthening contribution of these particles was derived as a function of the particle radius and the particle volume fraction.

Simulations of Dislocation Glide in Overaged Precipitation-Hardened Crystals. V.Mohles Philosophical Magazine A, 2001, 81[4], 971-90