2001 Volume 42 Issue 7 Pages 1293-1300
The influence of the raw powder characteristics and cold compaction on the solid-state synthesis of Mg2Si from elemental Mg–Si mixture powder has been examined by thermal analysis using DSC thermogram. The Mg2Si synthesis progresses at the lower temperature range when employing the fine Si powder, because of the increase in the contacting area between the Mg and Si particles. MgO film, covering the Mg powder surface, prevents the Mg2Si synthesis due to its thermal stability, however SiO2 surface film is not so effective because of the deoxidization by Mg during heating. Concerning the effect of the compaction pressure, when the hard Si particles are embedded in the Mg powder after compacting the mixture powder, the mechanical breakage of the thermally stable MgO surface film occurs. Therefore, the enlargement of the contacting clean area between the particles causes the progress of the Mg2Si synthesis at the lower temperature. Based on these results, the bulk mechanically alloyed Mg–Si composite powder, in which the fine Si particles are distributed uniformly in the Mg matrix, shows a decrease of the reaction temperature by 350 K compared to the mixture powder.