Thermal Behavior of AZ31 and Si in Solid State Synthesis of Mg2Si

Abstract

Mg2Si/Mg composite which shows high mechanical properties was expected to be produced via solid-state synthesis using AZ31 powder and Si powder as initial material. For the first step of this research, thermal behavior of AZ31 and Si was investigated in this paper.AZ31/Si compacts with various compositions were examined by differential scanning calorimeter and analyzed by X-ray diffraction to confirm reactability between them.The detailed result indicated that Si could completely react with AZ31 and synthesize Mg2Si when heated at 753 K, which is almost the same temperature as in the case of using purity Mg. The starting temperature of synthesis became lower and exothermic heat increased as Si content increased. Repeated plastic working (RPW) was also effective to decrease their synthesizing temperature. That is because the reaction between Mg and Si occurred easily due to the mechanisms of RPW process such as (1) breakage of oxide film on the surface of Mg particles and (2) refinement of both of the Mg and Si particles. In addition, it was observed as the result of optical microstructure that Mg2Si particles were dispersed into matrix and they existed at the interface of Mg grain.