Microstructure and corrosion resistance of high-pressure solidified Mg-11Al Alloy
摘要
Mg-11 wt%Al alloy was prepared by high-pressure solidification, and the corrosion resistance of the alloy was studied based on experiments and first-principles calculations. For the alloy solidified at 6 GPa pressure, remarkable grain refinement occurs in α-Mg phase, and the number of β-Mg17Al12 phase decreases by 80% compared to the alloy solidified at atmospheric pressure. In addition, the solid solubility of Al atoms in α-Mg increases from 5.11 wt% at atmospheric pressure to 17.34 wt% at 6 GPa. The electrochemical tests show that the potential difference of α- mg/grain boundary decreases by 61 mV because the β-Mg17Al12 phase at grain boundaries transforms into Al solute enrichment zone, so the driving force of galvanic corrosion is reduced. Moreover, the Volta potential of the alloy increases from 35 mV to 1.386 V. Furthermore, first-principles calculations show that the work function increases (3.61 → 3.63 eV) owing to larger Al solid solubility, which confirms the improvement of the resistance to uniform corrosion at the electron level. In summary, the corrosion rate of the alloy decreases from 61.5 mm/a (at atmospheric pressure) to 4.6 mm/a (at 6 GPa) due to more solid solubility of Al atoms, phase interface reconstruction and uniform electrochemical behavior caused by high pressure.