Spectral Analysis for Estimating the Electrochemical Behavior of High-Entropy GdTbDyHoSc and GdTbDyHoY Alloys

The electrochemical behavior of disordered systems, such as high-entropy alloys, is a stochastic random process. To accurately predict and analyze the behavior of such systems under operating conditions, it is necessary to use new computational and experimental methods along with classical electrochemical methods. Using equimolar rare-earth alloys GdTbDyHoSc and GdTbDyHoY as an example, we demonstrate the efficiency of using fast Fourier transform and wavelet analysis to estimate the electrochemical behavior of stochastic systems. The time series of potential fluctuations of alloy samples are measured in 0.01 M NaCl solution within 12 h at a current density of 0.2–0.5 mA/cm 2 . Fast Fourier transform analysis of the obtained time series shows that the slope of the logarithm of spectral power density to the logarithm of frequency increases with the current density. In particular, coefficient β changes from –1.93 to –1.77 for a GdTbDyHoY sample and from –1.46 to –1.35 for a GdTbDyHoSc sample. In addition, wavelet analysis is used to process the time series obtained for both alloys at current densities from 0.2 to 0.5 mA/cm 2 . To illustrate the intensity of the electrochemical dissolution of the alloy surface, we construct scalograms for the obtained time series. The scalograms are used to calculate the global energy spectra distributed over frequency ranges and the total energies of the systems under study. The GdTbDyHoY alloy exhibits higher total energies as compared to the GdTbDyHoSc alloy. The total energy for the GdTbDyHoY alloy increases from 0.97 to 2.03 kV 2 when the current density increases from 0.2 to 0.5 mA/cm 2 . For the GdTbDyHoSc alloy, the total energy increases from 0.50 to 0.84 kV 2 . Fast Fourier transform and wavelet analysis are found to be effective tools for understanding the electrochemical behavior of locally disordered chemical systems, such as high-entropy GdTbDyHoSc and GdTbDyHoY alloys, in addition to classical electrochemical methods.