NON-SCHMID EFFECTS ON THE BEHAVIOR OF POLYCRYSTALS - WITH APPLICATIONS TO NI3AL

The elastoviscoplastic single crystal constitutive model incorporating non-Schmid effects developed by Dao and Asaro (Mater. Sci. Eng. A, 19 93, vol. 170, pp. 143-60) is introduced into Asaro and Needleman's (Ac ta Metall., 1985, vol. 33, pp. 923-53) Taylor-like polycrystal model a s well as Harren and Asaro's (J. Mech. Phys. Solids, 1989, vol. 37, pp . 191-232) finite element polycrystal model. The single crystal non-Sc hmid effects, strain hardening, latent hardening, and rate sensitivity , are all described on the individual slip system level, while polycry stal mechanical properties on macroscale are predicted. In general, it is found that non-Schmid effects can have important influences on the ''constant offset plastic strain yield surfaces,'' stress-strain beha vior, texture development, and shear band formation. Finite element ca lculations show that with moderate non-Schmid effects, localized defor mation within a polycrystal aggregate tends to initiate earlier and fo rm sharper and more intense shear bands. Heavy shear banding is found to produce less pronounced textures, which is consistent with existing experimental evidence on Ni3Al. Examples with Ni3Al demonstrate that the kind of non-Schmid effects existing in Ni3Al can increase the gene ralized Taylor factor to values much higher than 3.06, raise the polyc rystal strain hardening rate much higher than that which would be obta ined using Schmid's rule, and influence the deformation texture.