Revisiting Precipitation kinetics in Mg-Zn alloy – a multi-characterization and modeling study

This work aims to provide new insights into understanding precipitation kinetics in Mg-Zn alloys. First, the evolution of Zn solute, precipitate size and volume fraction is characterized using a combination of thermoelectric power, X-ray diffraction, atom probe tomography and transmission-electron microscopy in an Mg-1.7at.%Zn alloy when aged at 150 °C and 200 °C. The experimental results are then supported by a precipitation model based on classical nucleation and growth theories for rod and plate-shaped precipitates. It is found that rod-shaped precipitates are prevalent in the early aging stage, while plate-shaped precipitates dominate the over-aging stage. The kinetics of both precipitates are depicted in detail to represent this competition. Finally, a time-temperature-transformation diagram for these two types of precipitates is proposed for this system.