Influence of planar defects on powder diffractograms of fcc metals

Abstract

X-ray powder diffractograms from fcc crystals containing high concentration (more than 1%) of planar defects [deformation stacking faults (SF), double deformation SF, twin boundaries (TB)] have been simulated by Monte Carlo method in kinematic approach. It was shown that the characteristics of powder diffraction peak profiles (except peaks with indexes H00) dependent nonmonotonically on PD concentration, during which peak maximums stay in Bragg positions. An addition point to emphasize is that an appearance of TB only in the crystal not affects on position of all peaks. Several types of PD to be occurred simultaneously in the crystal influence on powder diffractograms additively. Peculiarities of the powder diffraction pattern inherent in different types of PD have been revealed to permit predominant PD type to be found with a high degree of accuracy based on experimental data.

In‐Situ Study of the Microstructure Development in a CrMnNi TRIP Steel During Plastic Deformation

“…8). This asymmetry of the XRD line (220) is an indicator of the presence of the stacking faults 14–17 that is plausible with the findings of TEM.…”

“…HRXRD experiments were carried out both as radial (2θ/Ω) and azimuthal (Ω) scans. The radial scans revealed changes in the asymmetry of the XRD lines that were attributed to the different density of stacking faults 14–17. The azimuthal scans were performed at different inclinations of the sample from the symmetrical position and at a fixed detector position for the (220) line of austenite and disclosed small local lattice rotations as caused, e.g., by certain dislocation structures.…”

Reinforcing Mechanism of Mg‐PSZ Particles in Highly‐Alloyed TRIP Steel

“…This can be seen by the advancing broadening of the 110α′ XRD peak. Naturally, the 200 peak of the γ‐austenite broadens significantly and shifts to smaller diffraction angles as a result of the increased stacking fault content within the fcc austenite phase 26. The increasing stacking fault density is related to the appearance of hexagonal diffraction lines 24, which are used to be assigned to the ε‐martensite 27.…”

A total scattering Debye function analysis study of faulted Pt nanocrystals embedded in a porous matrix

“…A probabilistic approach to the occurrence of single, double deformation and twin faults was introduced several decades ago by defining three independent , and parameters, the (approximate) effect of which on peak shifts and broadening has been derived numerically (Wilson, 1942;Warren, 1990). As beautifully summarized by Ustinov & Budarina (2002), the occurrence of these defects induces different, though weak, effects, depending on the reflection parity. In particular, while twin deformations do not significantly affect the peak positions, single and double deformation faults induce measurable shifts, the sign of which, for the most prominent 111 and 200 peaks, clearly suggests the predominance of one type of deformation versus the other.…”

“…However, complex hybrid systems are commonly obtained and, even though the analysis is restricted to the structural and microstructural characterization of the metal nanocrystalline component, conventional X-ray diffraction methods, which inherently disregard the amount of information from the diffuse scattering, may provide a limited outcome. The investigation may be further complicated by the structural defectiveness of metal nanoparticles, which frequently exhibit faulting deformation (Hall, 2000;Zanchet et al, 2000;Ustinov & Budarina, 2002;Cervellino et al, 2003Cervellino et al, , 2004Beyerlein et al, 2010;Beyerlein, Leoni et al, 2011;Scardi et al, 2011;Longo et al, 2014), and by possible surface relaxation effects (Wasserman & Vermaak, 1972;Diao et al, 2003;Qi & Wang, 2005;Gelisio & Scardi, 2014;Scardi & Gelisio, 2016), occurring at their very small sizes. Moreover, even if the geometrical constraints of the host template are expected to induce the formation of (elongated) NCs within the channels, metal nanoparticles may also form on the surface of the silica matrix, the two ensembles being difficult to distinguish by conventional analytical/ imaging methods.…”