The Mg–Zn–Si system: Constitutional properties and phase formation during mechanical alloying

The isothermal section of the Mg–Zn–Si system at 300 °C was determined through the characterization of annealed samples by means of scanning electron microscopy, electron probe microanalysis and X-ray powder diffraction. No ternary phases have been detected in this system at 300 °C. The Mg2Si phase was found to dissolve about 2 at.% Zn, changing its lattice parameter from a = 0.6347(4) nm to a = 0.6335(4) nm; the other binary phases do not form detectable solid solutions with the third element. Based on the results obtained on samples subjected to different thermal treatments a U-type invariant equilibrium is proposed to occur in the solid state at 350 < T < 380 °C. Si powder blends of two different compositions were mechanically alloyed in a planetary ball mill. In both cases the milling process promoted solid state reactions between the constituent elements, leading to the formation of multiphase samples containing crystalline Mg–Si and Mg–Zn binary phases.