Observation of ε′-Ag₁₇Mg₅₄ phase induced by plasma immersion ion implantation

This paper provides a confirmation of the effectiveness of the recently suggested ab initio approach to the theoretical prediction of phase transformations which may be induced in metallic alloys by metal plasma immersion and ion implantation processing. The approach is based on an assumption that at certain concentrations of the implanted species, the relaxation of the exited electronic state of the implanted structure should be accompanied by the rearrangement of atoms leading to the formation of a new phase. Recently, on the basis of density functional theory calculations of the energetic characteristics of the electronic subsystems of the implanted Mg-Ag system, it was predicted that concentrations of the implanted Ag ions within the range from ∼18 to 23 at% Ag, favor transition to the phase ε′-Ag₁₇Mg₅₄. Our transmission electron microscopy observations and electron diffraction analysis of the Mg-based alloy subjected to the implantation of Ag ions at dose of ∼5×10¹⁵ ion/cm² confirmed that the formation of the ε′-Ag ₁₇Mg₅₄ phase indeed takes place.