Influence of Long-Period Stacked Ordered Phases on Inductive Impedance of Mg-Gd-Y-Zn-Zr-Ag Alloys

Abstract

In this paper, the influence of long-period stacked ordered (LPSO) phases on the electrochemical impedance spectroscopy (EIS) of a Mg-Gd-Y-Zn-Zr-Ag alloy in 0.9 wt.% NaCl was investigated. The Mg-6Gd-3Y-1Zn-0.5Zr-0.3Ag (wt.%) alloy samples with and without LPSO phases in the grain interior (HOMO and LPSO, respectively) were prepared using different heat treatments. The EIS results showed that both the HOMO and LPSO samples’ Nyquist diagrams contained two inductive loops. However, in the Nyquist plots of the LPSO samples, the inductive loops at 1.71–0.67 Hz appeared in the first quadrant rather than the fourth quadrant. Analysis of the fitting parameters illustrated that the abnormal shape of the inductive loops is related to greater values of the surface film capacitance Cf and double layer capacitance Cdl in the LPSO samples. Further investigations through corrosion morphology observation indicated that the greater values of Cf and Cdl in the LPSO samples resulted from the existence of intragranular LPSO phases that created more film-free areas. The above results show that a better understanding of the relationship between the inductive impedance and corrosion morphology of a Mg-6Gd-3Y-1Zn-0.5Zr-0.3Ag alloy in 0.9 wt.% NaCl solution was attained.

The Development of a High-Strength Mg-10.3Gd-4.4Y-0.9Zn-0.7Mn Alloy Subjected to Large Differential-Thermal Extrusion and Isothermal Aging

“…The magnitude and spacing of blocky LPSO phases were too large to allow them to directly interact with dislocations and promote strengthening [ 43 ]. Instead, short fiber reinforcement was primarily generated by the blocky LPSO phase [ 44 , 45 ]. The E3 alloy exhibited a smaller blocky LPSO phase and a more diffuse Mg 5 (Gd, Y) phase, resulting in stronger strengthening ( ) compared to the E2 alloy by ~37 MPa.…”

“…The magnitude and spacing of blocky LPSO phases were too large to allow them to directly interact with dislocations and promote strengthening [43]. Instead, short fiber reinforcement was primarily generated by the blocky LPSO phase [44,45]. The E3 alloy exhibited a smaller blocky LPSO phase and a more diffuse Mg5(Gd, Y) phase, resulting in stronger strength- In addition, the average lengths of blocky LPSO phases measured lengthwise to the ED in the E2 and E3 alloys were about 20 and 14 µm, respectively, with the average spacing values perpendicular to the ED being about 10 and 8 µm, respectively.…”