Digital Image Correlation of 2D X-ray Powder Diffraction Data for Lattice Strain Evaluation.

Lattice strain measurement is a common practice in materials science. Traditional methods involve converting 2D X-ray powder diffraction data into 1D profiles. This conversion is necessary for full pattern refinement but is not always efficient. When only peak center positions are needed, the conversion process introduces unnecessary complexity. Errors may arise from radial binning or fitting procedures during conversion. These errors can affect the accuracy of strain evaluation. Prior research has shown that 2D to 1D conversion is a standard but not always optimal approach. No prior work had resolved how to bypass this step while maintaining accuracy. This gap motivated the development of a new direct analysis method.

The aim of this study is to propose a new method for lattice strain evaluation. The method avoids the need for 2D to 1D conversion of X-ray diffraction data. The researchers propose using Digital Image Correlation (DIC) directly on 2D X-ray powder diffraction patterns. This method is named XRD-DIC for short. The motivation is to simplify the analysis process and reduce potential errors. The study compares XRD-DIC results with conventional 'caking' and fitting procedures. The goal is to demonstrate that XRD-DIC provides reliable strain values. The study also aims to show that this method enables full in-plane strain evaluation.

The researchers developed a new method called XRD-DIC. This method applies Digital Image Correlation to 2D X-ray powder diffraction patterns. The process skips the traditional 2D to 1D conversion step. Instead, the analysis is performed directly on the 2D data. As a test case, the method was applied to a Mg AZ31B alloy bar after 3-point bending. Strain values along the central line were calculated using XRD-DIC. The same data was also analyzed using the conventional 'caking' and fitting procedures. The results from both methods were compared to assess agreement and reliability.

The XRD-DIC method produced strain values that matched well with the conventional 'caking' and fitting results. The comparison showed excellent agreement in strain values across different azimuthal angles. The principal strains and their directions were calculated using multiple direction data. This allowed for full in-plane strain evaluation. The XRD-DIC approach simplified the analysis process by eliminating the 2D to 1D conversion step. The method proved to be reliable and robust for strain evaluation. It reduced the potential for errors introduced during conversion and fitting. The results suggest that XRD-DIC is a valid alternative to traditional methods.

The study concludes that XRD-DIC is a reliable and robust method for strain evaluation. The results from XRD-DIC matched well with conventional methods. The method simplifies the analysis process by skipping the 2D to 1D conversion step. This reduces the potential for errors in radial binning or fitting. The XRD-DIC approach enables full in-plane strain evaluation. The researchers propose that this method opens new possibilities for data analysis. It provides a more efficient way to evaluate strain from 2D powder diffraction data. The study suggests that XRD-DIC is a valid alternative to traditional methods.