A dislocation kinetics-based analysis has been carried out on the toughening mechanisms of alloys. It is concluded that both improved strength and toughening can be achieved through adjusting the short range interatomic interactions between embedded solute atoms, or other point defects, that affect Peierls-Nabarro energy barrier, and the long range interactions between dislocation loops and heterogeneities such coherent precipitates, second phase particles, and crystallography; the latter determines dislocation loops’ patterns such as kink-jog formation. In order to quantify the effects of lattice heterogeneities, a variation principle that defines the energy minima of dislocation line configuration has been derived, which includes the effects of three-dimensional stress states and crystallography, instead of the conventional line energy-based Eular formulation that only considers the case under shear stress. This provides an analytical means and associated numerical tool to determine the favorite dislocation loop’s patterns in an alloy. The further analysis reveals that double-kinks within single slip-plane have limited effect on toughening while the corresponding bow-out solution may lead to a lower-bound estimate of precipitate strengthening. Therefore, a proposed strategy for toughening is to create dispersed softening centers in strengthened matrix that trap accumulated dislocation loops in the form of mixed double-kinks and jog-induced climbings, for example, helices. These kinds of dislocation patterns are able to spread out localized dislocations from single or close packed parallel slipping planes to many cross-over planes in multiple slip-systems, so as to delay the formation of shear bands while maximize the magnitude of bowing-out induced strengthening.

This content is only available via PDF.
You do not currently have access to this content.