Flow stress in small volumes decreases with the diameter increase, which is called size effect. The size effect is known to be attributed to the dislocation nucleation, mutual interaction of dislocations, and dislocation-surface interactions. Recently, another attention has been paid extensively to the size effect in alloys. In this case, dislocation-precipitate interactions can be another important factor affecting the size effect. Therefore, in order to explore the entire physical picture of the size effect in alloys, it is necessary to understand the role of the dislocation-precipitate interactions in determining the flow stress in small volumes. In this study, we develop a new dislocation dynamics-based computational method to investigate the dislocation behavior in alloy-micropillars, which address the dislocation interaction with the other dislocations, surfaces, and precipitates. The numerical results of the simulation using the developed method suggest that there are two yielding modes. The first mode results from the critical shear stress for dislocation sources. The second mode is the single-armed dislocation source. The modes are controlled by the length of the dislocation source and spacing between the dislocation source and the surface. Moreover, the flow stress of the alloy-micropillar is larger than the micropillar without precipitates as the result of the dislocation-precipitate interactions.
Saito et al. (Wed,) studied this question.