Evaluation of the jogged-screw model of creep in equiaxed γ-TiAl:: identification of the key substructural parameters

On the basis of microstructural observation of 1/2[110]-type jogged-screw dislocations, it has been previously proposed that the creep deformation mechanism in equiaxed gamma-Ti-48Al alloys is controlled by the climb of the jogs on these dislocations. This is validated by predictions from a creep model based on these observations. However, several assumptions made in the model were not fully substantiated by experiment or theory. The aim of this study is to verify and validate the parameters and functional dependencies assumed in the model. In addition, the original solution has been reformulated to take into account the finite height of the moving jog. The substructural model parameters have been further investigated in light of this reformulation. The stress dependence of dislocation density, jog spacing and jog height has been evaluated via simulations, analytical modeling and experimental observations. Combining all of these parameters and dependencies in a reformulated model leads to an excellent prediction of creep rates and stress exponents. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.