High-Throughput Evaluation of Hardening Coefficients of Eight Alloying Elements in Magnesium

Liquid-solid diffusion couples (LSDCs) are employed to generate a composition gradient in the single-phase hexagonal closed-packed (hcp) solid solution with compositions up to the solubility limit of various solutes in Mg. Nanoindentation scanning across the composition gradient in LSDCs allows effective evaluation of composition-dependent hardness of eight alloying elements (Al, Ca, Ce, Gd, Li, Sn, Y, and Zn) in the hcp Mg phase. The hardening coefficients, an indicator of the potency of solid-solution hardening, are evaluated from the measured composition-hardness data and correlated with various materials properties such as atomic radius, shear modulus, and elastic modulus of the solutes. The rank of hardening potency of Al, Gd, Sn, Y, and Zn measured by nanoindentation is in good agreement with that measured by microindentation reported in the literature. The hardening coefficient (potency) from the strongest to the weakest is Ce > Ca > Y approximate to Gd > Zn > Al approximate to Sn > Li in Mg-based hcp binary solid solutions. The hardening coefficient is found to be closely correlated with the strengthening potency.