A Forest Model of Latent Hardening and its Application to Polycrystal Deformations

This paper means to assess latent hardening effects on large-scale polycrystal deformation on the basis of the dislocation theory of plastic flow and of a wide variety of experimental observations on single crystals. The qualifier large-scale is introduced to eliminate effects during the earliest stages of flow, where mono- and polycrystals behave differently: the authors will not consider easy glide in single crystals; and they will not consider the gradual transition, over perhaps ten times the elastic strain, to polyslip in polycrystals; or, for that matter, initial Lueders-type deformation in polycrystals. In terms of dislocation theory, they will consider the flow stress to mean the percolation limit of dislocations in areal glide. Dislocation theory will be used at a rather gross level. Experience has shown that many of the details of the interactions between dislocations and of their arrangement are of surprisingly little influence on macroscopic plastic behavior. They will present a latent hardening model that is based on the well established forest model of flow stress and strain hardening. They will present a latent hardening model that is based on the well established forest model of flow stress and strain hardening. They will then assess various pieces of experimentalmore » and theoretical evidence that limit the number and magnitude of the parameters and predict the direction in which they might depend on stacking-fault energy. Finally, they will summarize results obtained by polycrystal simulation in which the model was implemented. They show only marginal effects, and only in certain cases.« less