Analysis of EET on Ca increasing the melting point of Mg17Al12 phase

The present investigation showed that the additions of Ca to the alloy AZ91 were mainly dissolved into the Mg₁₇Al₁₂ phase and increased its melting point and thermal stability, which would have great effects on the high-temperature properties of AZ91 alloy. The empirical electron theory (EET) of solid and molecules was used to calculate the valence electron structures (VES) of Mg₁₇Al₁₂ intermetallic compound with and without Ca addition. The results showed that Ca dissolving in Mg₁₇Al₁₂ phase increased the strength of bonds that control the thermal stability of Mg₁₇Al₁₂ phase. Additions of Ca also made the distribution of the valence electrons on the dominant bond network more uniform in the whole unit cell of Mg₁₇Al₁₂. The theoretical conclusions well account for the experimental results.