CONSTITUTIVE MODELING OF LL2 INTERMETALLIC CRYSTALS

A dislocation model of the hardening of L1(2) intermetallics is proposed. Hardening is presumed to be the net effect of point obstacles opposing the motion of dislocations. Two sources of point obstacles are considered: forest dislocations and cross-slip pinning. Forest hardening is assumed to be the only operative hardening mechanism for cubic systems. Octahedral systems are presumed to be subject to both forest hardening and hardening by cross-slip pinning. The rate of obstacle generation by die latter mechanism is taken to be proportional to the rate of cross-slip. The activation enthalpy for cross-slip is taken from the work of Paidar et al. (V. Paidar, D. P. Pope and V. Vitek, Acta Metall., 32 (3) (1984) 435). Detailed comparisons between theory and experiment are given. The theory correctly predicts salient aspects of the behavior of L1(2) intermetallics, including features which had previously been interpreted as indicative of ''non-Schmid'' yield behavior.