Evolution of Phase Transformations in the Mg-Ni-Ce System After Mechanical Synthesis and Spark Plasma Sintering.

The present study focuses on investigating the evolution of phase transformations in the Mg-Ni-Ce system under the influence of mechanical synthesis (MS) and spark plasma sintering (SPS). Magnesium powder mixtures with different nickel and cerium contents (Mg-3%Ni-2%Ce, Mg-7%Ni-3%Ce, and Mg-10%Ni-5%Ce) were mechanically activated along with various grinding parameters. The X-ray phase analysis (XRD) has shown the successive stages of the phase formation in the MS process: from the initial components to the formation of intermetallic compounds of MgNi, MgNi, and CeMg. An increase in the intensity of mechanical treatment facilitated the accelerated destruction of the crystal lattice, the generation of defects, and the formation of new phases, as evidenced by the broadening and reduction in the intensity of Mg diffraction peaks. The subsequent SPS stage promoted the completion of phase transformations, structural stabilization, and the formation of a dense, multicomponent microstructure with a uniform distribution of intermetallic compounds. The observed average crystallite sizes ranged from 20 to 70 nm, depending on the processing conditions. The research results demonstrate the possibility of targeted control over the phase composition, opening new opportunities for the development of highly efficient hydrogen-absorbing alloys.