Finding Short Range Order in High Entropy Alloys

In this project, chemical short-range order in four samples of the high entropy alloy FeMnAlC was investigated. X-ray diffraction measurements were performed at the Advanced Photon Source of Argonne National Laboratory in Chicago, IL. The data were then analyzed by curve fitting with mathematical Gaussian and Lorentzian functions. Conditional fitting was applied to the first and fourth samples to confirm the original curve fit. Conditional fitting was then used to adjust the determined indices of the Gaussian peaks in these samples so that they better reflected what was occurring in nature. From these indices, an increased unit cell was predicted with four atoms, further confirming chemical ordering. The peak width of the Gaussian and Lorentzian peaks in each of the four samples was found by determining the full width at half maximum (FWHM). Using the FWHM, the number of unit cells in short-range ordering was calculated for each of the peaks. The peak height was also examined to determine the strength of short-range ordering. The strength of short-range ordering for each of the peaks in the four samples was then ranked from highest to lowest. Finding short-range order can give information that helps explain the mechanical properties of high entropy alloys. Because of their exceptional properties, applications of high entropy alloys include various fields such as aerospace.