A seminar given by
Enseignante-Chercheuse à La Rochelle Université, LaSIE (France)
titled:
Interaction between point-defects and dislocation
Abstract: The plastic properties of crystalline materials are not solely determined by the presence of defects within the crystal structure, but also by the interactions between these defects. In metals, the interactions between point defects and dislocations have been extensively studied and are known to play a crucial role in various mechanical behaviors. For instance, at low or moderate temperatures, point defects significantly influence strain hardening or softening and strain ageing. At higher temperatures, the absorption or emission of point defects along the dislocation lines enables dislocation climb and thus impacts creep. Understanding these interactions is essential for predicting and controlling the mechanical behavior of crystalline materials. The aim of this presentation is to introduce methods for investigating the interaction between dislocations and point defects at different scales. We will explore these methods in the context of several crystalline materials, including aluminum, magnesium oxide, and iron, and examine the interaction for edge and screw dislocations with various point defects such as vacancies and hydrogen.
Dislocations are extended defects with a complex core structure that varies depending on the material. Hence, to fully capture the intricacies of the core and its local interactions with point defects, atomic-scale simulations are necessary. In particular, Density Functional Theory (DFT) simulations are a crucial step in capturing the electronic effects that arise when point defects are located within the dislocation core [1]. Point defects may be trapped by the core, which can hinder dislocation motion influenced by the Peierls barrier which depends on the presence of point defects. They may also experience accelerated diffusion through pipe diffusion mechanism. Alternatively, point defects can be absorbed by the core and participate in dislocation climb, which can affect the material’s creep behavior [2]. In order to accurately simulate the effect of defect concentration on dislocation glide or dislocation climb, larger-scale simulations in time and space are thus necessary. In these cases, an empirical potential approach using molecular dynamic or kinetic monte carlo simulations can be used to describe the interactions between point defects and dislocations, both at short and long ranges.
However, these simulations are extremely computationally expensive and cumbersome. When the distance between a point defect and a dislocation is large enough, their interaction can be modeled within the framework of elasticity theory [3], which is less computationally demanding than atomic-scale simulations. Studies have shown that a good agreement between theory and simulation results can be achieved using an approach based on elasticity theory and the dipole elastic approach [3, 4]. This approach enables us to describe not only the interaction between point defects and the dislocation’s far elastic field but also the diffusion of point defects [3, 5].
[1] Allera, Ribeiro, Perez and Rodney, Phys. Rev. Materials 6 (2022) 013608
[2] Landeiro, Proville, Marinica and Sauzay, Phys. Rev. Materials 4 (2020) 103603
[3] Clouet, Varvenne, Jourdan, Comput. Mater. Sci. 147 (2018) 49-63
[4] Landeiro, Carrez, and Cordier, Phys. Rev. Materials 5 (2021) 063602
[5] Landeiro, Giret, Carrez and Cordier, Comput. Mater. Sci. 211 (2022) 111490
*Corresponding author: mlandeirATuniv-lr.fr (M. Landeiro Dos Reis)
