Revisiting Precipitation kinetics in Mg-Zn alloy – a multi-characterization and modeling study
Yi Yang, V. Massardier, Mahmoud Reza Ghandehari Ferdowsi, Lu Jiang, Jun Wang, Thomas Dorin, Sitarama R. Kada, Matthew Barnett, Michel Perez
Abstract
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.