Balancing Microstructural Refinement and Electrochemical Homogeneity in ECAP-Processed Mg-Y-Zn Alloys via Mn/Zr Microalloying

This study reveals the synergistic effects of Mn and Zr microalloying and equal-channel angular pressing (ECAP) on the microstructure and corrosion behavior of Mg-Y-Zn alloys in Hanks’ solution. At moderate deformation levels (four passes), the alignment of LPSO phases forms semi-continuous barrier structures, promoting the formation of dense corrosion product layers and improving corrosion resistance. (e.g., Mg-Y-Zn-Mn 4p: 1.07 mm·y−1). However, excessive deformation (eight passes) leads to severe fragmentation of LPSO phases, increasing cathodic activity and intensifying micro-galvanic coupling in Mn-containing alloys (Mg-Y-Zn-Mn 8p: 2.61 mm·y−1). In contrast, Zr-containing alloys exhibit continuous improvement in corrosion resistance with increasing ECAP passes, attributed to enhanced electrochemical uniformity resulting from homogeneous ultrafine-grained structures (Mg-Y-Zn-Zr 8p: 0.87 mm·y−1). These findings elucidate the critical mechanism by which the interplay between microalloying chemistry and severe plastic deformation governs electrochemical uniformity and corrosion kinetics. This work provides new insight into the corrosion behavior of ECAP-processed Mg-Y-Zn alloys, highlighting the critical role of balancing microstructural refinement and electrochemical heterogeneity, and offers guidance for the optimization of corrosion-resistant Mg-based materials.