Line Profile Analysis Method Research Articles

XRD as an Alternative Technique for Cation Distribution Characterization of MFe2O4 Magnetic Nanoparticles

This work focuses on utilizing the X‐ray diffraction technique as an alternative method to specialized and high‐cost techniques such as X‐ray photoelectron spectroscopy to obtain the cation distribution in magnetic nanoparticles as MFe2O4 with spinel structure synthesized by thermal decomposition. X‐ray diffraction measurements for MFe2O4 with M = Co2+ as transition cation (inverse spinel CoFe2O4) showed sensitivity to the cation distribution for octahedral and tetrahedral sites in this material with this kind of crystalline structure, being a good option for its determination. The cation distribution was obtained from the X‐ray diffraction intensity ratios for the most sensitive crystalline planes to the cations in octahedral and tetrahedral sites. Besides, the Debye–Scherrer equation and line profile analysis method from the diffraction pattern were used to determine the size distribution and the crystallite size. The size distribution obtained by X‐ray diffraction was from 15 to 18 nm, while transmission electron microscopy was found to be from 10 to 25 nm. The inversion degree x derived from X‐ray diffraction exhibits variability within the interval 0.6 < x < 0.8, not very far from that obtained by X‐ray photoelectron spectroscopy (x = 0.67). This material exhibits a saturation magnetization of 124.88 emu g−1. Consequently, the X‐ray diffraction technique opens the possibility of obtaining reliable information related to nanoparticles’ morphological and chemical properties with spinel structure.

Fractional densities and character of dislocations in different slip modes from powder diffraction patterns

Irradiation induced dislocation loops and lattice dislocations produced by plastic deformation have very different dipole characters, dislocation contrasts and range of strain fields. To determine partial dislocation densities of the different dislocation types from X-ray or neutron diffraction patterns, all differences in dislocation properties should be considered. We have extended the convolutional multiple whole profile line profile analysis method to convolve different strain profiles with different effective outer cut-off radii, corresponding to different dislocation type, into a single size profile. The extended procedure is applied to determine the 〈a〉 loop and lattice dislocation densities in a neutron irradiated and tensile deformed Zr-2.5 %Nb alloy and in a proton or neutron irradiated Zircaloy-2 alloy. We show that when the dislocation densities are very different the effective outer cut-off radius of dislocations is a better descriptor of dislocation character than the dislocation arrangement parameter, which was used previously in line profile analysis. Our results show that the combination of line profile analysis and electron microscopy methods provides a detailed and comprehensive description of defect structures in deformed and irradiated materials.

Microstructure of Gear Steels Treated by Shot Peening by X-Ray Line Profile Analysis Method

Microstructure of Gear Steels Treated by Shot Peening by X-Ray Line Profile Analysis Method

Experimental analysis of deformation texture evolutions in pure Cu, Cu-37Zn, Al-6Mg, and −8Mg alloys at cold-rolling processes

Generally, two types of deformation textures of copper-type and brass-type textures are evolved in face-centered cubic (FCC) metals. During deformation, dislocation motion determines which texture will be dominant. The copper-type texture is formed in metals of high stacking fault energy by cross-slip of dislocations and subsequent dislocation cell formation. On the other hand, deformation twinning involves the brass-type texture evolution, whereas some exceptions, such as Al-Mg alloys, also have been reported. This study examined deformation texture evolutions in four cold-rolled FCC alloys of pure Cu, Brass (Cu-37Zn), Al-6Mg, and Al-8Mg alloys. Electron backscattered diffraction and X-ray line profile analysis methods investigated the deformation texture evolution. Three different strains of 0.25, 0.45, and 0.63 were applied to observe the strain effect on texture evolution. In pure Cu, the copper-type texture is developed, as commonly known. The brass-type texture is developed in Brass and Al-Mg alloys. More reduction ratios in those alloys lead to the copper-type texture strengthening in pure Cu, whereas stronger brass-type texture is shown in Brass and Al-Mg alloys by applying more reduction. While the brass-type texture evolution in Brass can be illustrated by deformation twinning, deformation twins are absent in deformed Al-Mg alloys despite their evident brass-type texture formation. Instead, the short-range ordering (SRO) mechanism can explain the brass-texture evolution in Al-Mg alloys. Planar slips by the high Mg content of Al alloys strengthen the rotated Goss orientation with brass-type texture evolution after cold-rolling processes of those alloys.

Post irradiated microstructure and mechanical properties of pure V

Proton irradiation has been carried out on pure vanadium samples and the changes in the microstructure and mechanical properties have been evaluated as a function of dose. The microstructural parameters such as domain size and microstrain have been assessed along different crystallographic planes using the X-ray diffraction line profile analysis methods such as simplified breadth and the modified Rietveld technique. No significant change in the dislocation density is observed as a function of dose from the XRD results. However, the results of positron annihilation spectroscopy in terms of positron lifetime and S-parameter clearly indicated the formation of small defect clusters with irradiation. Transmission electron microscopy investigation confirmed the presence of small dislocation loops in the irradiated samples. Molecular dynamics simulations carried out to model the formation of irradiation-induced defects clusters with irradiation dose support the experimental observation of small defect clusters and increasing cluster size with dose. The yield strength and tensile strength showed systematic increase with irradiation dose corroborating with the results of microhardness measurement. The fractography of the tensile samples clearly showed the characteristics of brittle fracture in the irradiated samples.

Residual Stress Heterogeneity Induced By Powder Metallurgy Gear Manufacturing Chains

Powder metallurgy represents an alternative to increase sustainability in the manufacturing of automotive gears, but its potential is hindered by a certain lack of knowledge on surface integrity properties that can impair the gear performance. This study explores the effects of the microstructural differences induced by this chain on the residual stress heterogeneity state of gears. X-ray diffraction methods of macro residual stress mapping and line profile analysis were applied for measurements of gear teeth after subsequent steps of the powder metallurgy and the conventional wrought steel chains. The powder metallurgy chain induced more pronounced heterogeneities than the conventional manufacturing, characterized by non-uniform residual stress distributions along the lead and the involute profiles of gear flanks. These non-uniformities observed after carburizing were traced back to the previous steps, surface densification, sintering and compaction. The residual stress distribution patterns of these steps were compatible with the plasticity dynamics of each manufacturing process. Such surface integrity heterogeneities result in a residual stress gradient along the gears functional surface, exposing particular regions to be more susceptible to fatigue effects.

Strain anisotropy models for refined diffraction line profile analysis in cubic metals

Abstract The present work examined the anisotropy magnitudes obtained from different elastic models of cubic metals (Cu, 5383 Al alloy, FCC austenite steel and BCC steel) to explore the origin of strain anisotropy. The results showed that stable intersections were observed from the modeled and experimental plots of the reciprocal elastic modulus (1/Ehkl) and orientation parameter (Γ). The effectiveness of quasi elasto-plastic model based method in correcting strain anisotropy was further verified in cold-worked specimens. For the important input parameters in dislocation model based diffraction line profile analysis methods, the average diffraction contrast factors of dislocations were observed to depend on elastic constants. Interesting intersections were found from linear dependence of on Γ. The conventional input values indicated distinct dependencies on given elastic constants in diffraction line profile analysis. Accordingly, a refined approach was proposed by adopting the optimized intersections as input values, by which more reliable results could be obtained in practical applications.

Effect of stacking fault energy on the evolution of microstructure and texture during blast assisted deformation of FCC materials

Effect of stacking fault energy (SFE) on microstructural and crystallographic aspect of high-velocity deformation of FCC metals (Ni, Cu, and austenitic stainless steel) via blast assisted deformation have been investigated in this work. Microstructural changes have been probed via XRD line profile analysis and electron back-scattered diffraction methods along with TEM analysis for selected samples. The texture of all deformed material tends towards a developed α-fiber, which is observed to be strain-dependent. The relative fraction of Brass to Goss texture components increases with a decrease in SFE. The annealing twin boundaries, present in the initial material, transform in segments or full to high angle random boundary in all the material due to the dislocation pile-up. However, the microstructure of the deformed material depends heavily on the SFE, with nickel showing dislocation cells, and, austenitic stainless steel (ASS) has a mix of features of homogeneous dislocation, deformation bands, and deformation twins. Relatively thick deformation twins form in grains having orientations other than {110} plane normal to the blast direction. The overall microstructure of ASS gives an impression of a superimposed microstructure. Such structure is expected to be a result of shock passage through the material followed by macroscopic straining. No such superimposed microstructure has been observed in nickel which is attributed to recovery behavior prevalent in high SFE materials.

Dislocation densities in cold worked copper by electron and X-ray diffraction methods

ABSTRACTElectron backscatter diffraction (EBSD) and X-ray diffraction line profile analysis (XLPA) methods are suitable to determine dislocation densities within crystalline structures. A software was developed to obtain dislocation density from misorientations measured between the adjacent points by EBSD. However, this EBSD-based method can estimate only the density of geometrically necessary dislocations (GND), while XLPA method can give the total dislocation (TD) density. In this paper, GND densities are determined and compared them to the TD densities in as-received and severe plastic deformed copper samples. Based on these results, estimations are tested to provide reliable GND densities and to appreciate the applicability of this calculation method. Furthermore, correlations are found between TD densities and yield strengths estimated by hardness tests.

Investigation on microstructure and properties of Al18B4O33 whisker reinforced Al[sbnd]Mg[sbnd]Si matrix composite after shot peening

This work investigated the influences of two-step shot peening on the residual stress fields, microstructure, microhardness and corrosion performance of aluminum borate (Al18B4O33) whisker reinforced AlMgSi matrix composite by X-ray stress tester, X-ray diffraction line profile analysis method, transmission electron microscopy (TEM), Vickers analyzer and electrochemical examinations, respectively. The results indicate that shot peening induces considerable compressive residual stress (−151 MPa) and satisfied microstructure refinement into the near surface region. The domain sizes gradually increase from the top surface to the substrate, the microstrain and dislocation density present the contrary variation trends. The maximum microhardness locates at top surface and the value is about 2.5 times that of matrix. Furthermore, shot peening improves the corrosion performance of Al18B4O33 whisker reinforced AlMgSi matrix composite. The sample with a peening intensity 0.40 + 0.08 mmN possesses the best corrosion behavior with maximum polarization resistance (15133 Ω cm2) and lowest corrosion current density (2.202 μA cm−2). The refined domain size and compressive residual stress should account for the improvement of corrosion behavior. However, further increasing shot peening intensity, the corrosion resistance drops, which is considered as a consequence of induced surface defects, increased surface roughness and dislocation density.

Analysis of recrystallization behavior of shot peened graphene reinforced Al composites during isothermal annealing by X-ray diffraction method

Graphene reinforced Al matrix composites (G/Al) with high mechanical property was successfully reported. However, there are quite limited studies about the recrystallization behavior of these new composites after plastic deformation. Here, the recrystallization behaviors of shot-peened surface layer of G/Al composites and Al during isothermal annealing were investigated by using X-ray diffraction line profile analysis method. The microstrain, domain size, dislocation density at different annealing conditions were calculated. The results revealed that besides annealing temperature and time, the existence of graphene reinforcement also played an important role for its microstructure evolution. Based on the results of X-ray diffraction line profile analysis, the microstrain relaxation energy and recrystallization activation energy of G/Al composites and Al were calculated by computer regression analysis, respectively. It showed that microstrain relaxation energy and recrystallization activation energy of G/Al composites were higher than that of Al, which can be ascribed to the reinforcement's impeding movement of dislocations, grain and subgrain boundaries in the process of recrystallization. The effect of graphene reinforcement on the variation of relative texture coefficient and microhardness was also distinct. Based on above results, it can be concluded that the existence of graphene reinforcement may enhance the thermostablity of deformed G/Al composites.

INVESTIGATION OF SURFACE GRADIENT MICROSTRUCTURE OF SHOT PEENED S30432 STEEL BY X-RAY LINE PROFILE ANALYSIS METHOD

S30432 steels were processed by multistep shot peening treatment. The refined microstructures, including domain size, microstrain, domain size distribution and texture were characterized by X-ray diffraction (XRD) line profile analysis method, respectively. The results demonstrate that in the deformed layers, a gradient structure is formed after shot peening. The domain size reaches 25[Formula: see text]nm at the surface, then it decreases as the depth increases, but microstrain (0.0027) is the largest at the surface. The domain size distributions at different depths calculated by Rietveld method are consistent with domain size variation along the depth. There are no strong textures after shot peening treatment. The change of microhardness along the depth is in accordance with the gradient microstructure. It is expected that this work can offer useful information for characterizing the microstructure of shot peened materials.

An improved X-ray diffraction analysis method to characterize dislocation density in lath martensitic structures

An improved X-ray diffraction line profile analysis method is developed to determine dislocation density of lath martensitic steels. This method combines the modified Warren–Averbach (MWA) and the modified Williamson–Hall (MWH) methods. The developed method is robust and leads to unique values for the dislocation density, the effective outer cut-off radius of the dislocations (Re) and the dislocations distribution parameter (M). Dislocation structures of lath martensite in a steel, in the as-quenched condition as well as in tempered conditions, are characterized by using the proposed method. The calculated dislocation density is compared with the values obtained from the MWH method by considering a constant value for M. It was found that both methods provide dislocation densities in the range of the values calculated from the dislocation strengthening component of the yield strength.

Dislocation Effects on the Diffraction Line Profiles from Nanocrystalline Domains

A Pd nano-polycrystalline microstructure was simulated by molecular dynamics, including edge or screw dislocations in one of the 50 grains, so as to produce a realistic model of nanocrystalline domain with line defect. The same crystalline domain was also studied, with or without line defects, as a free-standing, isolated nanocrystal. Atomic coordinates of the selected domain were used to generate powder patterns by means of the Debye scattering equation, and these patterns were used as “experimental” data to test existing methods of line profile analysis in controlled condition, i.e., with known type and density of defects. Results show that the Krivolgaz–Wilkens theory of dislocation line broadening qualitatively agrees with the MD model, but errors can be larger than 50 pct. A critical issue arises from the instability of the Krivolgaz–Wilkens model when all line profile parameters are simultaneously refined: reasonable results can be obtained by fixing or restricting some parameters.

Microstructure and texture of electrodeposited Ni–ZrC composite coatings investigated by Rietveld XRD line profile analysis

Rietveld X-ray diffraction (XRD) line profile analysis method was used to investigate the influence of applied current density on the microstructure and texture of the electrodeposited Ni–ZrC composite coatings. Crystallite size, microstrain, distribution of crystallite size, dislocation density, crystalline preferred orientation (texture), and ZrC particles content of the Ni–ZrC coatings were obtained from the Rietveld XRD line profile analysis. The results show that the crystallite size of Ni–ZrC coating increases, the microstrain and dislocation density decrease with the increasing of the current density. And the distribution of crystallite size is less uniform at higher current density. The pole figures simulated by Rietveld analysis software are coincident with the measured pole figures of Ni–ZrC coatings. The calculated relative texture coefficient (RTC) values, the simulated and measured pole figures of the coatings all illustrate that the texture of Ni–ZrC coating is modified from weak (220) to strong (200) texture with the increasing of applied current density. The microstructure evolution of Ni–ZrC composites is ascribed to the change of applied current density and ZrC content in the coatings.

SiNx thickness dependent morphology and mechanical properties of CrAlN/SiNx nanomultilayers

CrAlN/SiNx nanomultilayers with different SiNx layer thicknesses were synthesized by reactive magnetron sputtering. The microstructure and mechanical properties were investigated by X-ray diffraction, high-resolution transmission electron microscopy and nano-indentation techniques. The average crystallite size, microstrain and average dislocation density of CrAlN/SiNx nanomultilayers with different SiNx layer thicknesses were evaluated by X-ray diffraction line profile analysis method. The results indicated that, when SiNx layer thickness was below 0.6nm, SiNx was forced to crystallize and grew epitaxially with CrAlN layers, resulting in the decrease of average dislocation density and the enhancement in hardness and elastic modulus. As the SiNx layer thickness further increases, the epitaxial growth was firstly interrupted and then crystallized SiNx layers transformed back to amorphous state, leading to the increase of average dislocation density and the decrease of hardness and elastic modulus. An energy balance model was established to explain the microstructure evolution.

Thermostability of S30432 shot peened surface layer

The recrystallisation behaviour of S30432 shot peened deformation surface layer during isothermal annealing has been investigated by X-ray diffraction line profile analysis method. The results revealed that annealing time and temperature were two key parameters for isothermal annealing process of S30432 steel. With higher annealing temperature, the recrystallisation behaviour in the shot peened deformed layer was more obvious. Based on the results of line profile analysis, the recrystallisation activation energy and microstrain relaxation energy were calculated. In addition, after isothermal annealing, the depth distribution of domain size in the deformed layer was also investigated and discussed in details. According to the analysis, the results showed that the thermostability of S30432 shot peened surface layer was relatively stable when the annealing temperature was below 650°C.

Grain growth studies on nanocrystalline Ni powder

The microstructure of nanocrystalline Ni powder produced by ball-milling and its thermal stability were investigated by applying different methods of X-ray diffraction line-profile analysis: single-line analysis, whole powder-pattern modelling and the (modified) Warren–Averbach method were employed. The kinetics of grain growth were investigated by both ex-situ and in-situ X-ray diffraction measurements. With increasing milling time, the grain-size reduction is accompanied by a considerable narrowing of the size distribution and an increase in the microstrain. Upon annealing, initial, rapid grain growth occurs, accompanied by the (almost complete) annihilation of microstrain. For longer annealing times, the grain-growth kinetics depend on the initial microstructure: a smaller microstrain with a broad grain-size distribution leads to linear grain growth, followed by parabolic grain growth, whereas a larger microstrain with a narrow grain-size distribution leads to incessant linear grain growth. These effects have been shown to be incompatible with grain-boundary curvature driven growth. The observed kinetics are ascribed to the role of excess free volume at the grain boundaries of nanocrystalline material and the prevalence of an “abnormal grain-growth” mechanism.

Surface mechanical properties of S30432 austenitic steel after shot peening

The surface yield strength of S30432 austenitic steel after conventional and dual shot peening treatments has been investigated by means of X-ray stress analysis. The results showed that the proof stress σ0.2 of the shot peened surface increased to around 830MPa and 940MPa after conventional and dual shot peening, respectively. While for the bulk S30432 austenitic steel, the yield strength was 268MPa. The strengthen mechanism was discussed in terms of microstructure by X-ray line profile analysis method. The results revealed that the refined domain size and high micro-strain were induced in the deformed surface layer. This changed microstructure was mainly responsible for the high yield strength of shot peened surface. The surface yield strength of the material surface can be obtained from the proposed X-ray stress analysis method. Therefore, this method can be considered as a complementary approach in investigating the microstructural hardening effect of SP treatment.

Atomistic interpretation of microstrain in diffraction line profile analysis

A virtual X-ray powder diffraction experiment is conducted on a realistic computer-generated nano-polycrystalline microstructure. It is shown that the size and strain broadening contributions to the diffraction line profiles can be directly and reliably extracted from the atomistic model. It is also shown that current line profile analysis methods cannot fully interpret the observed patterns due to the peculiar microstructure of grain boundaries.