Scientific Reports: New progress in the creep mechanism of Mg-RE alloys
MAR 7,2021 Li Jin
Limited creep resistance in Mg alloys has restricted their widespread usage for decades. One critical strategy enhancing the creep performance is to add RE elements to achieve solid solution alloys. However, the conventional elastic interaction fails to explain the abnormally higher solid solution strengthening of RE elements compared to other solutes in Mg.
To further explore the strengthening mechanism, the role of dislocation-solute interactions on the creep behaviour of binary Mg-RE alloys were systematically investigated by Professor Dong Jie’s team from the National Engineering Research Center of Light Alloy Net Forming of Shanghai Jiao Tong University. HAADF-STEM was utilized to obtain the atomic scale information in the as-extruded Mg-0.5Ce and Mg-2Gd (wt.%) alloys. A transition of the creep mechanism from dislocation climb for the Mg-0.5Ce alloys to solute drag dislocation glide for the Mg-2Gd alloys has been verified even under the same temperature of 200 ℃ and the similar ratio of the applied stress to the yield stress. The results show that the low solid solubility and faster diffusion rate of Ce lead to almost no Ce atoms left in the Mg matrix upon high temperature extrusion. However, the interactions between dislocations and Gd atoms are detected in the as-extruded Mg-2Gd alloys. Such interactions can not only exert a drag effect on the dislocation motion and enhance the strengthening effect offered by the hexagonal dislocation patterns, but also lead to the formation of dynamic precipitation. In this case, dislocation-Gd atoms interactions are crucial for the high creep resistance of the Mg-2Gd alloys.
Relevant results were published in Scientific Reports with the title "The Role of Dislocation-solute Interactions on the Creep Behaviour of Binary Mg-RE Alloys". Link to the original article is https://www.nature.com/articles/s41598-021-82517-5. The first author of the paper is PhD student Jing Li, and the corresponding author is Professor Li Jin. The research was funded by the National Key Research and Development Plan and the National Natural Science Foundation of China.
Fig. 1. Creep performance of Mg-0.5Ce alloys (a-d) and Mg-2Gd alloys (e-h).
Fig. 2. Characterization of dislocations in the steady-state creep stage of Mg-0.5Ce alloys (a-b) and Mg-2Gd alloys (c-f).
Fig. 3. Characterization of dislocation-solute interactions in the steady-state creep stage of Mg-0.5Ce alloys (a) and Mg-2Gd alloys (b-f).