Synergistic regulation of texture and second phases to enhance the mechanical properties and long-term corrosion resistance of friction stir processed Mg-14Gd-0.6Ce-0.5Zr alloy

In this study, friction stir processing (FSP) was employed to modify the as-cast Mg-14Gd-0.6Ce-0.5Zr alloy, and the effects of texture evolution and distribution of second phases on mechanical properties were systematically investigated. The results show that friction stir processing effectively refined the coarse Mg₅Gd phases into nanoscale second phases uniformly distributed along grain boundaries. The synergistic effect of texture weakening and second phases refinement significantly enhanced the tensile strength and elongation of the FSP-1000-120 alloy to 302.1 MPa and 18.3%, respectively, representing increases of 20.8% and 281.3% compared to the as-cast alloy. The as-cast alloy has a lower corrosion rate in the initial stage due to fewer micro-galvanic corrosion sites. However, the uniform distribution of the second phase in the FSP-treated (FSPed) alloy contributes to the formation of a more complete and dense corrosion product film. After 120 h of immersion, the as-cast alloy forms deep pits due to the continuous dissolution at the second phase-matrix interface, with the average corrosion rate increasing from 0.31 to 0.47 mL/cm²/h. The long-term corrosion rates of FSP-1000-60, FSP-1000-120, and FSP-1200-120 samples are stable at 0.36, 0.43, and 0.50 mL/cm²/h, respectively. Research reveals that FSP regulates texture and second phase distribution to achieve synergistic strengthening of alloy strength plasticity, and the homogenization of second phase distribution is a key factor in improving the long-term corrosion resistance of alloys.