Hidden flaw found in how scientists measure metal alloys used in engines and tools
Researchers discovered that a standard laboratory technique for analyzing the atomic structure of engineering alloys produces misleading results when materials have directional crystalline patterns—a condition that occurs during normal manufacturing. The finding could affect quality control processes and materials development across aerospace, automotive, and industrial manufacturing sectors.
Originaltitel: Effect of crystallographic texture on pair distribution function analysis in engineering materials
Physical properties of alloys are known to be affected by local order on the atomic scale; however, since this structural feature appears on sub-nanometer to nanometer scale, characterization of it is inherently challenging. Interest in local order in metallic systems has increased in recent years, driven by the development of increasingly compositionally complex alloys and observation of phenomena that cannot be explained by microstructural changes alone. One way to study local order is through the total scattering technique, an extension of powder diffraction where Bragg scattering and diffuse scattering are analyzed, often primarily through the pair distribution function. The calculation of a pair distribution function assumes an ideal powder with randomly oriented crystallites (i.e., without texture), which is rarely the case for conventionally processed engineering materials. Texture has numerically been shown to affect an arbitrary pair distribution function, but the effect has not been explored in depth across different alloy systems. In this work, we investigate the effect of texture on pair distribution functions for typical engineering materials through simulations, validate the simulation results with experimental data, and investigate potential artificial short-range order effects that may arise in large box models when texture is present. We show that different types of texture introduce perturbations in real space, which in turn affect model fitting within the Reverse Monte Carlo modelling framework. Based on this work, we conclude that samples for which the presence of texture cannot be excluded, through experimental setup or data reduction methods, are not suitable for standard PDF analysis.