COLLECTIVE BEHAVIOR AND SUPERDISLOCATION MOTION IN L12 ALLOYS

A simulation of superdislocation motion applicable to L1(2) intermetal lic alloys displaying the yield stress anomaly has been developed. The simulations incorporate a cross-slip-pinning mechanism and allow dire ct study of the spatial and temporal correlations between pinning even ts. The predicted dislocation structures agree well with available exp erimental observations. The relationship between the pinning-point cor relations and the mechanical properties of the alloys is explicitly in vestigated. The superdislocations are shown to undergo a stress-driven , non-equilibrium phase transition. The critical exponents of the tran sition are shown to be related to strain hardening. Theoretical predic tions for the exponents are in excellent agreement with the algebraic form of primary creep transients for Ni3Al within the temperature rang e of the flow strength anomaly. The importance of treating dislocation -level phenomena on an equal footing with detailed microscopic mechani sms is stressed.