Role of the LPSO structure in the improvement of corrosion resistance of Mg-Gd-Zn-Zr alloys.

Abstracts The role of long period stacking ordered (LPSO) structure in the corrosion behavior of Mg-Gd-Zn-Zr alloys was investigated by means of potentiodynamic polarization experiments, hydrogen evolution tests, and microstructure characterization. The corrosion rate of the Mg-Gd-Zn-Zr alloys is mainly determined by the acceleration effect of the second phases in the micro-galvanic corrosion. After T4 heat-treatment, the β-(Mg,Zn) 3 Gd eutectic phase in the as-cast Mg-Gd-Zn-Zr alloys transforms into an X phase with a 14H-LPSO structure. According to the results of scanning Kelvin probe force microscopy (SKPFM), the potential difference between LPSO phase and the α-Mg matrix is 243 mV, whereas, it is 290 mV between the eutectic phase and matrix in the as-cast alloys. The low relative potential and volume fraction of the LPSO phase reduce the acceleration degree of micro-galvanic corrosion. As a result, the corrosion resistance of Mg-Gd-Zn-Zr alloys improves significantly by the LPSO structure. Highlights • Corrosion rate of T4 treated alloys with LPSO structure is extremely lower than as-cast alloys without LPSO structure. • Micro-galvanic corrosion dominates the corrosion behavior of Mg-Gd-Zn-Zr alloys. • LPSO phase can improve the corrosion resistance of Mg-Gd-Zn-Zr alloys significantly due to its lower potential. [ABSTRACT FROM AUTHOR]