Synthesis and thermal stability of nanocrystalline Mg-6Al-1Zn-1Si alloy prepared via mechanical alloying

Thermal stability and the kinetics of the grain growth of nano-crystalline Mg-6Al-1Zn-1Si alloy prepared via mechanical alloying (MA) were investigated. It started with elemental powders, using a variety of analytical techniques including differential scanning calorimetry (DSC), X-ray diffraction method (XRD), and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). The results showed that MA-processed alloy was composed of an Mg-based supersaturated solid solution with small amounts of Al and MgAl2O4. Grain growth and Mg2Si precipitation occurred upon annealing of the MA-processed Mg-based alloy. Nevertheless, grain growth in the MA-processed alloy was limited and α-Mg grains with sizes in the range of 70 nm were still present after exposure to 450 °C. The grain growth behavior of alloy can be described by the parabolic kinetic equation of grain growth. Higher strength values obtained after hot consolidation can be due to refined microstructure and the formation of Mg2Si intermetallic phase.