Nonisothermal dissolution kinetics on Mg17Al12 intermetallic in Mg-Al alloys

Abstract

In this work, nonisothermal dissolution of intermetallic Mg17Al12 in Mg-Al alloy has been firstly studied via Differential Scanning Calorimetry-DSC, X-Ray Diffraction-XRD and Scanning Electron Microscope-SEM as well as CALPHAD_based dissolution models and molecular dynamics simulation. The size and volume fraction of Mg17Al12 phase could be predicted via the present kinetic dissolution model and agree well with experimental results. Also, the data-driven screening calculation shows that there is a range of temperature for significantly dissolving Mg17Al12 phase, which could be increased with the increase of heating rate. The evolution of structural order for Mg17Al12 phase has also been performed via molecular dynamics simulation with LAMMPS. The simulated results indicate that the structural order of Mg17Al12 phase during heating is mainly affected by the Al-contained atomic pairs (Al-Al and Al-Mg), suggested that Mg atoms are thermodynamically and kinetically more active than Al atoms in Mg17Al12 phase during heating, which has also been approved via the calculated atomic mobility of Mg and Al atoms in Mg17Al12 phase in this work. Therefore, the atomic mobility of Mg atoms is mainly attributed to the interdiffusion coefficient of Mg17Al12 phase which determines the dissolution of Mg17Al12 phase during heating. The fundamental principle in this work could be used for other intermetallics and offers the greatly valuable information for optimizing the thermal processing in application of metal structural materials.

Keywords

• Mg-Al alloy
• Intermetallics
• Dissolution model
• CALPHAD
• Molecular dynamics simulation