Advanced microstructural engineering through thermo-mechanical processing for enhanced corrosion resistance in Mg-Gd-Y alloys

Magnesium alloys with Gd and Y alloying have emerged as promising materials for various critical applications due to their excellent strength-to-weight ratio and mechanical performance. However, their corrosion resistance often hinders their broader adoption, necessitating advanced strategies to optimize their performance. This study explores the potential of a surface thermo-mechanical process, friction stir processing (FSP), in tailoring the corrosion behavior of Mg-Gd-Y alloys through microstructural engineering. The prime focus of this study is to look into the role of rare-earth elements distribution and grain refinement on the corrosion performance. Results demonstrate that FSP effectively reduces grain size from 302.36 to 10.05 mu m in the material with 4% alloying of Gd and Y. Differential scanning calorimetry (DSC) analysis suggests that the temperature during FSP was higher than the dissolution temperature of the alloy's intermetallic phases (282-375 degrees C), which improved the solid solubility of rare-earth elements (REE) in the Mg-matrix thereby facilitating their redistribution and minimizing the intergranular segregation. X-ray photoelectron spectroscopy (XPS) analysis suggests that suppressed micro-galvanic coupling and promoted formation of stable Mg/REE oxide layers leads to better corrosion performance. Multi-pass FSP processing strategy led to further microstructural refinement and superior corrosion resistance of 0.18 mm/year. The study opens up a potential research direction in exploring surface microstructural engineering as a promising technique for developing corrosion-resistant Mg alloys.