Individual effect of Y and Nd on the microstructure formation of Mg-Y-Nd alloys processed by severe plastic deformation and their effect on the subsequent mechanical and corrosion properties

This work investigated the effect of sole yttrium and neodymium alloying on the microstructure formation during severe plastic deformation by equal channel angular pressing (ECAP) and an impact on the mechanical strength and corrosion resistance of binary Mg-3Y and Mg-3Nd alloys. The results are compared with a ternary Mg-4Y-3Nd alloy, which represents a simplified version of the commercially successful WE43 alloy. The extensive study comprises a thorough microstructural analysis performed by scanning and transmission electron microscopy, including electron backscatter diffraction and texture analysis performed by X-ray diffraction. It is shown that the presence of Nd primarily caused precipitation during the processing of the Mg-3Nd alloy, while Y remained dissolved in the magnesium matrix in the Mg-3Y alloy. This difference resulted in a significantly smaller average grain size in the Mg-3Y alloy (∼0.77 nm) than in the Mg-3Nd alloy (∼1.3 µm) after the final step of the processing and formation of a slightly different texture. Consequently, the composition and the processing affected the mechanical and corrosion properties of the investigated materials, measured by compression deformation tests, microhardness measurement, and electrochemical impedance spectroscopy. This study shows that the ECAP-processed W3 sample exhibits a surprisingly good combination of ultrafine-grain structure, weak crystallographic texture, high strength, and high corrosion resistance compared with the other investigated samples. These attributes make this material very interesting for utilisation in the industry and/or medicine.