Atomistic characterization on the solute clustering and precipitation of Mg alloysWednesday (08.11.2017) 11:20 - 11:40 Part of:
Magnesium alloys have important applications in the automotive and aerospace industries because of their high specific strength for the weight reduction and better fuel economy. However, the mechanical properties of conventional Mg alloys are often not suitable for high temperature applications. The addition of heavy rare-earth (HRE) elements can greatly improve the high temperature performance of Mg alloys, which can be directly correlated to the different type solute clusters and precipitates formed during the aged treatment. However, these solute clusters and precipitates have not been systemically characterized. Furthermore, there is a lack of the solute partitioning information into the precipitates. In this contribution, transmission electron microscopy (TEM) and atom probe tomography (APT) were employed to characterize the solute clustering and precipitates in Mg-Zn-Gd based alloys. TEM characterizations and APT analyses reveal that the roles of Gd are threefold: (i) forming Gd-containing ternary phase, and thereby partly consuming Gd, (ii) partitioning into the precipitates, and thereby increasing the number density of precipitates, decreasing the size of precipitates, and improving the thermal stability of precipitates, and (iii) increasing the eutectic temperature of the alloy, and thereby increasing the solution treatment temperature, dissolving more solutes into the Mg matrix, and enhancing the ageing hardening. These careful TEM characterizations and quantitative atom probe data analyses give us some hints to design novel Mg alloy and optimize some important Mg alloy in service.