Based upon the embedded atom method, a study was made of dislocations by-passing nanophases in a model for face-centered cubic alloys. A system in which either a purely screw or a purely edge dislocation crosses Ni3Al nanophases with L12 order in a Ni single crystal was employed as an archetypal case for strengthened face-centered cubic alloys. For a radius up to 1.5nm the dislocations cut the nanophase and the de-pinning stress was found to be proportional to the area of the nanophase. For larger radii, the dislocation circumvents the nanophase and leaves an Orowan loop around the inclusion with the de-pinning stress increasing as the logarithm of the inclusion radius, in agreement with predictions drawn from an analytical theory proposed by Bacon, Kocks and Scattergood (1973). The theory was extended to determine the logarithm pre-factor for the looping regime and the de-pinning stress needed to cut through the nanophase. The theoretical predictions were then compared to atomistic simulations.

Dislocation Depinning from Ordered Nanophases in a Model FCC Crystal: from Cutting Mechanism to Orowan Looping. L.Proville, B.Bakó: Acta Materialia, 2010, 58[17], 5565-71