Thermal stability and grain growth behavior of nanocrystalline Mg2Si

Thermal stability and grain growth behavior of nanocrystalline Mg2Si (nano-Mg2Si), prepared by using mechanically activated solid-state reaction plus hot-pressing in vacuum, were investigated by the method of in situ high-temperature X-ray diffraction. The result indicates that the evolution of grain size d with isothermal-annealing time t for nano-Mg2Si can be well described by the formula d − d0 = ct1/n with grain growth exponent n = 6, 5 and 4 at 700, 800 and 900 °C, respectively, indicating that nano-Mg2Si has a good thermal stability. Simultaneously, an Arrhenius plot of rate constant c against the reciprocal of T yields a straight line, from which an activation energy of 112 ± 1 kJ/mol is derived for the grain growth of nano-Mg2Si.