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

The isothermal section of the Mg-Zn-Si system at 300 degrees 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 degrees 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) mu; 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 degrees C. Mg-Zn-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. (C) 2010 Elsevier Ltd. All rights reserved.