Reliability and interpretation of the microstructural parameters determined by X-ray line profile analysis for nanostructured materials

Abstract

In this overview, the applicability of X-ray diffraction line profile analysis (XLPA) for the characterization of the microstructure in nanostructured materials is overviewed. The dislocation densities obtained by whole pattern fitting and from the breadth of the diffraction peaks are compared. Both theoretical considerations and experimental evidences prove that the evaluation of the peak breadth solely is not suitable for the determination of the dislocation density. In addition, the microstructural parameters determined by XLPA were compared to the values obtained directly by microscopic methods. It was found that the ratio of the grain size obtained by microscopy and the crystallite size determined by XLPA decreases with the reduction of the grain size in nanomaterials, and below $$\sim $$ ∼ 20 nm, the two values agree within the experimental error. In addition, correlation between the microstructural parameters (e.g., crystallite size and dislocation density) determined by XLPA was not found. It was revealed that bottom–up processing methods can produce similarly high defect density in nanostructured materials as severe plastic deformation (SPD). The influence of stacking fault energy, melting point, and degree of alloying on the microstructure of nanomaterials is discussed in detail.

Combinatorial Design of Novel Multiprincipal Element Alloys Using Experimental Techniques

“…[ 39 ] During XLPA, the width and shape of XRD profiles are evaluated which can yield the crystallite size distribution, the density, and the edge/screw character of dislocations as well as the planar fault probability in MPEAs. [ 40 ] These parameters are sensitive to the chemical composition of MPEAs as it has been revealed by former studies. [ 10,11,41 ] Combining synchrotron radiation experiment with ML‐XLPA, a full microstructure mapping of combinatorial samples can be performed within hours.…”

Nanostructuring of Multi-Principal Element Alloys by Severe Plastic Deformation: from Fundamentals to an Improved Functionality

“…In addition, the average size and size distribution of crystallites can also be obtained from XLPA. 51) This technique does not require complicated sample preparation and the statistics of the microstructural parameters obtained by this procedure is much better than that of the microscopic methods (e.g., transmission electron microscopy -TEM) due to the much larger probed volume. 50,51) In this study, mainly XLPA is used for the determination of the density of lattice defects formed during SPD, therefore some features of this technique specific to MPEAs will be discussed in the next paragraphs.…”

“…7 compares the defect densities of CoCrFeNi MPEA samples processed by 20 turns of HPT and physical vapor deposition (PVD). 51,69) In nanocrystalline MPEAs processed by bottomup methods, the dislocations and twin faults are grown-in lattice defects which form in order to reduce the mismatch stresses between nanograins.…”