Nonisothermal dissolution kinetics on Mg17Al12 intermetallic in Mg-Al alloys

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.(c) 2021 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University

Automated summary

In this study, the nonisothermal dissolution of intermetallic Mg17Al12 in Mg-Al alloy was investigated using DSC, XRD, SEM, CALPHAD-based dissolution models, and molecular dynamics simulation. The size and volume fraction of Mg17Al12 phase were successfully predicted by the kinetic dissolution model and matched well with experimental results. The screening calculation showed that there is a temperature range for significant dissolution of Mg17Al12 phase, which can be increased by increasing the heating rate. Molecular dynamics simulation revealed that the structural order of Mg17Al12 phase during heating is mainly influenced by Al-contained atomic pairs, suggesting the higher activity of Mg atoms compared to Al atoms. These findings provide valuable information for optimizing thermal processing in the application of metal structural materials.