Pressure Dependent Yielding in Solute Strengthened Aluminium
 - An Ab Initio Study

To describe the behaviour of dislocations in solute strengthened alloys subjected to tri-axial stress states, it is important to understand how a superimposed hydrostatic pressure affects the dislocation-solute interaction. A pressure dependent yield strength has been experimentally observed by Spitzig et al. [1]. They suggested that this is a result of a change in the energy barrier of dislocation motion, i. e. the mobility. The mobility is calculated by quantifying the solute-dislocation interaction energy, which in turn can be used as input in a solute-strengthening model.

In this work, the solute-dislocation interaction energy in aluminium is calculated using a combination of density functional theory and continuum elasticity theory. This is used as input in a parameter-free solute-strengthening model based on the work by Leyson et al. [2]. The model is general to fcc structures and applied to different solute elements, e. g. magnesium and silicon. By extending this model to account for a superimposed hydrostatic pressure, the pressure dependence on yield strength is investigated. This can bring insight to the mechanism associated with the strength differential effect. The aim is to get a better understanding of the role of dislocations in a solute-strengthened alloy.

[1]https://doi. org/10. 1016/0001-6160(75)90205-9
[2]https://doi. org/10. 1038/nmat2813