Pergramon PII S1359-6462(96)00348-X Scripta Materiaha, Vol. 36, No. 1, pp. 123-128, 1997 Elsevier Science Ltd CODWieht 0 1996 Acta Metalluraica Inc. %nkd in the USA. All rights kerwd 1359-6462197 $17.00 + .OO SIMULATION OF DISLOCATION CONFIGURATIONS IN THE PRESENCE OF MOBILE POINT DEFECTS A.N. Gulluoglu Department of Aerospace Engineering, Istanbul Technical University Maslak, Istanbul, Turkey (Received May 17,1996) (Accepted August 14, 1996) 1. Introduction The stress-strain curve of a material is a source of information reiated to mechanical properties of the materials. Some materials show serration between the elastic and homogeneous plastic region of the stress-strain curve. Such phenomenon reflects nonuniform deformation within the material. Because of the stress field of inhomogeneity within a crystal, dislocations will interact with them, which underlies the important role on the plastic deformation behavior of materials. A negative interaction energy between a dislocation and inhomogeneity causes a systematic migration of inhomogeneity to the dislo- cation at elevated temperatures. Thus, the dislocation is surrounded by atmospheres and demobilized, which is controlled by the diffusion rate of point defect. Under a sufftcient external force, the disloca- tion overcomes the anchoring force and starts to move. Once the dislocations are freed from their atmosphere, they rapidly flow which result in a serrated stress-strain curve. Mechanical behavior of crystalline materials can be understood by studying the strain rate dependence on stress and dislocation patterns produced during different deformation conditions in the presence of mobile point defects. Various studies on dislocation pattern formation under different deformation conditions have been carried out, e.g. by Lepinoux and Kubin( 1), Ghonhiem and Amodeo(2), Gulluoglu et al .(3), Gulluoglu and Hartley(4,5)1, and Van der Giessen and Needleman(6). In the present study, a new computer simu- lation model is developed, which provides a method of studying the formation of dislocation pattern and strain rate dependence on stresses in the presence of mobile point defects during a tensile test. This model considers dislocation-dislocation interaction forces, externally applied stresses, and interactions of point defects with dislocations. This work examines the effect of movement of point defects onto dislocations on strain rate and formation of dislocation structures during deformation. 2. Theoretical Basis of Simulations In the simulations, dislocations can move both along their slip plane and normal to it by glide and climb, respectively. The numerical simulations are restricted to a single slip system for simplicity. In the simulations, dislocations are represented by either 1 or T symbols, corresponding to positive or negative Burgers vectors, respectively. Point defects are represented by the symbol 0, in the model. 123