Atomistic modeling of the strengthening mechanisms in FCC and HCP metals

Abstract

Precipitate strengthening is one of the most efficient mechanisms to increase the yield strength of metallic alloys. Dislocation glide is hindered by the presence of a homogeneous dispersion of nm-sized intermetallic precipitates, and higher critical resolved shear stresses have to be applied on the slip plane to overcome the precipitate. Large precipitates (> 50 nm) are normally overcome by the formation of Orowan loops. In this case, the mechanisms of dislocation/precipitate interaction have been extensively analyzed in the past by means of continuum models based on the elastic interactions of the dislocation line with the precipitate. Smaller precipitates are often sheared by the dislocations and the associated strengthening mechanisms (chemical, stacking fault, elastic mismatch, coherency strains, and order) are more difficult to quantify. Moreover, the continuum hypothesis breakdown in the case of very small precipitates, such as Guinier-Preston zones.Classical atomistic simulations, based on either molecular statics or dynamics and path sampling methods, are another type of strategies that can be used to analyze the interaction mechanisms between dislocations and precipitates in the case of small precipitates (< 20 nm). Nevertheless, their application is not straightforward and requires to overcome several challenges: selection of the appropriate interatomic potential, building atomistic models with realistic interfaces between the precipitate and the vii ContentsResumen iii