Regulating elevated-temperature Portevin-Le Chatelier effect in wire-arc directed energy deposited GW102K Mg alloy through heat treatment

• This work first investigates tensile properties and deformation behavior of WA-DED Mg-Gd-Y-Zr alloy at elevated temperatures. • The Portevin-Le Chatelier (PLC) effect severity depends on tensile temperature and specific microstructural features. • RE-rich regions and dissolved solute atoms promote PLC, while solute depletion and nano-β' precipitates eliminate it. • Solution plus aging treatment achieves a combination of high strength and decent ductility, significantly surpassing traditional Mg-RE alloys. Wire-arc directed energy deposition (WA-DED) process, as an efficient and cost-effective additive manufacturing method, is emerging as a promising technique for fabricating high-performance Mg-Gd-Y-Zr alloys. However, most of the previous studies were limited to exploring the tensile performance at room temperature, which greatly restricted the practical application of such typical lightweight and heat-resistant metallic material at elevated-temperature service environment. Herein, this study investigates the tensile properties and deformation behavior of the as-deposited and heat-treated GW102K Mg alloy at various temperatures (room temperature, 200 °C, 300 °C) for the first time. The results indicate that elevated temperatures enhance ductility but reduce strength by promoting slip system activation, as indicated by the tensile properties. Notably, the tensile test temperature and microstructural characteristics determine the severity of the Portevin-Le Chatelier (PLC) effect. Specifically, the tensile test temperature influences the rates of both solute atoms' migration and dislocation annihilation, thus leading to an enhancement and then a decrease in the intensity of the PLC phenomenon. Particularly during elevated-temperature tension, rare-earth (RE) rich regions in the as-deposited samples and dissolved solute atoms in the solution-treated samples promote the PLC effect. Conversely, solute atom depletion and effective dislocation pinning by dense nano-β' precipitates eliminate PLC phenomenon in the solution plus aging-treated samples. Ultimately, the solution plus aging-treated sample achieves a combination of high ultimate tensile strength of 271 MPa along with a decent ductility of 11.1 % at 300 °C, substantially outperforming conventionally processed Mg-RE alloys. This study therefore offers guidance for regulating PLC effects in WA-DED Mg alloys for elevated-temperature applications.