First-principles data for solid-solution strengthening of magnesium: From geometry and chemistry to properties

Abstract

Solid-solution strengthening results from solutes impeding the glide of dislocations. Existing theories of strength rely on solutedislocation interactions, but do not consider dislocation core structures, which need an accurate treatment of chemical bonding. Here, we focus on strengthening of Mg, the lightest of all structural metals and a promising replacement for heavier steel and aluminum alloys. Elasticity theory, which is commonly used to predict the requisite solute-dislocation interaction energetics, is replaced with quantum-mechanical first-principles calculations to construct a predictive mesoscale model for solute strengthening of Mg. Results for 29 different solutes are displayed in a "strengthening design map" as a function of solute misfits that quantify volumetric strain and slip effects. Our strengthening model is validated with available experimental data for several solutes, including Al and Zn, the two most common solutes in Mg. These new results highlight the ability of quantum-mechanical first-principles calculations to predict complex material properties such as strength.

Solute strengthening in random alloys

“…For purposes of guiding alloy design, i.e. selection of solutes, Trinkle et al [39] devised two quantitative measures for the solute/dislocation interaction energy, a misfit volume parameter and a solute/stacking fault interaction parameter, and used these parameters in Fleischer/Friedel-type model to predict trends in solute strengthening at 0 K. Quantitatively predictive models have remained elusive. The long-range issue was only clearly addressed by the new theory presented in the following sections.…”

Nanoscale hydride formation at dislocations in palladium:Ab initiotheory and inelastic neutron scattering measurements

“…10 The dislocation core-where the continuum description of the strain fields breaks down-provides the largest distortions in geometry and the attraction of solutes to this region is crucial for solute effects on strength. [11][12][13] Tensile strain also lowers the vibrational excitation for H, and, in a dislocation core, broken symmetry splits the excitations. 14 The vibration of Pd next to H changes the local potential energy for each H atom, broadening the vibrational excitations.…”

Evaluation of Solid-Solution Hardening in Several Binary Alloy Systems Using Diffusion Couples Combined with Nanoindentation

“…The additional contribution to SSH can be attributed to the low SFE of Co. As mentioned in Section IV-A, the slip misfit e s [28] can be considered as an added contribution to e. Assuming a linear variation in SFE for the sake of argument, e s can be written as Dc c ; here, Dc is the difference between SFEs of FCC Ni (120 to 130 mJ/m 2 [37] ) and FCC Co (~10 mJ/m 2 [38] ), and c is the SFE of the solvent. Thus, it can be seen that e s could provide a significant contribution to k for Co (due to the low value of c), suggesting a possible explanation for the difference between the k values of Co and Ni alloys containing the same solute.…”

“…A probable explanation for this difference then is the contribution of chemical or slip misfit effect to SSH. This effect has been incorporated [28] [29] the slip misfit parameter can be expected to contribute to the high value of k.…”