Precipitation mechanism of Mg2Ni in Mg-Ni-Y studied by STEM, 3DAP and first-principles calculations.

The precipitation mechanism of nano-sized and micro-sized Mg 2 Ni particles during hydrogen-induced decomposition of 18R-type long period stacking ordered phase is investigated. Nano-sized Mg 2 Ni particles adhere to YH 2 particles inside grains, while micro-sized Mg 2 Ni particles form at grain boundaries due to the segregation of Ni atoms. The interface energies are predicted to be 1.108–1.263 J/m 2 for Mg/Mg 2 Ni, 1.389 J/m 2 for YH 2 /Mg 2 Ni, and 1.536 J/m 2 for YH 2 /Mg, indicating that the adhesion of nano-sized Mg 2 Ni to YH 2 reduces the total energy of the system. The negative segregation energy of −0.194 eV proves that the segregation of Ni atoms is energetically favorable. [ABSTRACT FROM AUTHOR]