Back-grinding Metallic Polycrystals for Improved X-ray Diffraction Patterns

Author(s):

Braden L. Miller, Joshua M. Cline, Michael T. Hurst, James D. Paramore, Anup Bandyopadhyay, Eli Norris, Trevor Hastings, Ibrahim Karaman, Raymundo Arróyave, George M. Pharr, and Brady G. Butler

Abstract:

The advancements made in X-ray diffractometer technology and the equations that were developed over the course of the 20th century have made modern X-ray diffraction (XRD) a quick and reliable technique for characterizing a material’s structure. Conventional sample types for XRD are monocrystals or powders; however, plenty of work has been done with polycrystalline materials. Each sample type has its own nuances: for polycrystals, grain size and orientation can cause issues during XRD experiments, and coarse grains and preferred orientations can lead to very few scanned crystallites that satisfy the Bragg criterion. This ultimately leads to low signal-to-noise ratios, missing peaks, and poor intensities in a scan. These issues can be compensated for by utilizing a simple back-grinding technique to increase the number of orientations that are queried during a scan. In this effort, a batch of coarse-grained high-entropy alloys were background on two sizes of silicon carbide abrasive pads to decrease the crystallite sizes and increase the orientations that satisfy the Bragg criterion during a scan. This introduces some peak-broadening; however, it also significantly improves the XRD patterns and results in more useful data.