Calorimetric analysis of AZ91D magnesium alloy

In order to study the activation energies and microstructure evolution of β-Mg₁₇Al₁₂ and eutectic structure in AZ91D magnesium alloy, calorimetric analyses were carried out using non-isothermal measurements by DSC and scanning electron microscopy (SEM) with EDX. During DSC tests, two peak temperatures of β-Mg₁₇Al₁₂ dissolution/precipitation and eutectic transformation were delayed in the heating/cooling process with the increase of scanning rates due to the occurrence of superheating/supercooling. Activation energies of β-Mg₁₇Al₁₂ dissolution and eutectic transformation were derived using multiple heating rates. Furthermore, the results of SEM and EDX revealed that the size and morphology of eutectic structures in the alloy had a close relationship with the time of β-Mg₁₇Al₁₂ phase dissolution during the heating process. More eutectic structures formed at low scanning rate due to sufficient time for the diffusion of Al in α-Mg regions.