XRD Line Profile Analysis Research Articles

ZnSe:Cu@ZnS core/shell quantum dots synthesis by photochemical method for ethanol gas sensing

In the present study, ZnSe, ZnSe:Cu and ZnSe:Cu@ZnS core/shell quantum dots (QDs) were synthesized at room temperature using the new and fast microwave-assisted photochemical approach recently reported by the authors. Gas sensors based on these QDs were made and their sensitivity was studied in response to different flows of ethanol gas. Morphology and elemental analyses (conducted via FESEM, TEM, EDS and Map) were performed alongside XRD line profile analysis using Halder-Wagner approach. TEM results showed that the synthesized QDs exhibited spherical morphology of particles with an average size of approximately 20 nm, except for ZnSe:Cu(1.5 %)@ZnS (including nanorods). Ethanol gas sensing measurements were conducted under ambient conditions. Coating the Cu (1.5 mol%)-doped cores with ZnS increased the sensitivity, while the undoped samples exhibited the opposite trend. Among the fabricated sensors, the most sensitive one was made of ZnSe without microwave irradiation (MWIR), although it lacked desired stability. Meanwhile, ZnSe:Cu(1.5 %)@ZnS nanorods were identified as the most sensitive (optimal) sample, demonstrating favorable stability. Consequently, the gas sensitivity of the optimal sample to various ethanol gas flow rates was tested. It was observed that gas sensitivity increased with increasing flow rate up to 150 ml/min and decreased somewhat at higher flow rates.

Medium-vacuum thermal evaporation of CdS:O thin films towards industrial CdS/CdTe solar cells: Temperature and O2% optimization

Oxygenated CdS thin films were deposited on Fluorine-doped Tin Oxide glasses by thermal evaporation technique at medium vacuum. The substrate temperature, source temperature and oxygen concentration at the ambient were varied to obtain optimum characteristics. The post-heat-treated thin films were subjected to optical, morphological and structural characterizations to achieve optimum deposition conditions. The optical bandgaps of this study were varied within 2.41–2.47 eV, and the highest average bandgap value of 2.47 eV was obtained from the CdS layer deposited at the substrate temperature of 150 °C, source temperature of 500 °C and 20% oxygen ambient. Crystallite size, microstrain and lattice parameters were obtained using XRD line profile analysis and the Pawley refinement technique. CdS/CdTe/Cu/Au solar cells were fabricated, and the highest average efficiency of 8.32% was observed from the CdS layers deposited with the above conditions.

Formability investigation of perforated austenitic SS 304L sheets using SPIF

Incremental sheet forming (ISF) is a progressive and highly flexible method of producing sheet metallic components in batches of limited quantities. It is also used for making prototypes at a low cost. Advantages of ISF are: higher sheet formability; elimination of molds and dies or use of simple molds and dies; formed parts with a good surface finish; use of commonly available vertical CNC milling machine and the possibility of quick changes in design. The low accuracy of formed parts and slow speed of the process are the disadvantages of ISF. Perforated metallic sheets have many applications in different industries because of their attractive display exposable to the atmospheric air and lighter weight than nonperforated metallic sheets. Its formability varies with the hole dimensions, ligament width, material chemistry, and forming parameters. In this paper, the effects of hole size, and other input parameters on the formability of the sheet are investigated. One millimeter thick SS 304L perforated sheets with 2 mm and 3 mm diameter holes are used for the present work. FLD and FLSD were drawn after performing the straight groove and wall angle tests. The highest formability was observed in the sheet with 2 mm diameter holes. XRD line profile analysis was done and correlated the formability with the crystallite size and dislocation density. SEM micrographs of fracture surfaces were taken and the fractographic parameters were correlated with formability. FE simulation was done using the optimized process parameters and the simulation results were compared with the experimental results. Contour and spiral tool path comparison was done numerically and experimentally.

Hierarchical Fe2O3 hexagonal nanoplatelets anchored on SnO2 nanofibers for high-performance asymmetric supercapacitor device

Metal oxide heterostructures have gained huge attention in the energy storage applications due to their outstanding properties compared to pristine metal oxides. Herein, magnetic Fe2O3@SnO2 heterostructures were synthesized by the sol–gel electrospinning method at calcination temperatures of 450 and 600 °C. XRD line profile analysis indicated that fraction of tetragonal tin oxide phase compared to rhombohedral hematite was enhanced by increasing calcination temperature. FESEM images revealed that hexagonal nanoplatelets of Fe2O3 were hierarchically anchored on SnO2 hollow nanofibers. Optical band gap of heterogeneous structures was increased from 2.06 to 2.40 eV by calcination process. Vibrating sample magnetometer analysis demonstrated that increasing calcination temperature of the samples reduces saturation magnetization from 2.32 to 0.92 emu g-1. The Fe2O3@SnO2-450 and Fe2O3@SnO2-600 nanofibers as active materials coated onto Ni foams (NF) and their electrochemical performance were evaluated in three and two-electrode configurations in 3 M KOH electrolyte solution. Fe2O3@SnO2-600/NF electrode exhibits a high specific capacitance of 562.3 F g-1 at a current density of 1 A g-1 and good cycling stability with 92.8% capacitance retention at a high current density of 10 A g-1 after 3000 cycles in three-electrode system. The assembled Fe2O3@SnO2-600//activated carbon asymmetric supercapacitor device delivers a maximum energy density of 50.2 Wh kg-1 at a power density of 650 W kg-1. The results display that the Fe2O3@SnO2-600 can be a promising electrode material in supercapacitor applications.

Microstructure and residual stress evolution in nanocrystalline Cu-Zr thin films

Grazing incidence X-ray diffraction (GIXRD) and scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDS) were employed to study the microstructure evolution and stress development in the nanocrystalline Cu100−X-ZrX (2.5 at% ≤ x ≤ 5.5 at%) alloy thin films. Small Zr additions to Cu led to significant lattice parameter anisotropy in the as-deposited Cu-Zr thin films both due to macroscopic lattice strain and stacking faults in the Cu matrix. Strain free lattice parameters obtained after the XRD stress analysis of Cu-Zr thin films confirmed formation of a supersaturated substitutional Cu-Zr solid solution. For the first time, the study of film microstructure by XRD line profile analysis (XLPA) confirmed progressive generation of dislocations and planar faults with increasing Zr composition in Cu-Zr alloy films. These microstructural changes led to the generation of tensile stresses in the thin films along with considerable stress gradients across the films thicknesses which are quantified by the traditional dψhkl−Sin2ψ and GIXRD stress measurement methods. The origin of tensile stresses and stress gradients in the Cu-Zr film are discussed on the basis of film growth and heterogeneous microstructure with changing Zr composition.

XRD Line Profile Analysis of Ball Milled ODS Ferritic Steel Powder Consolidated by Hot Isostatic Pressing

In this study, an ODS ferritic steel powder of composition Fe–12Cr–2W–1Zr–0.2Y (in wt %) was mechanically alloyed in a planetary ball mill, until the proper solid solution was established and consolidated by hot isostatic pressing. Basic microstructure features, in terms of the nature, density of the dislocations, lattice parameter and lognormal domain sizes distribution,—were determined by X-ray diffraction profile analysis, using the recent, powerful whole powder pattern modelling approach. XRD analysis revealed that microstructure during ball milling evolved towards the nanocrystalline state made of very fine, narrowly dispersed crystallites with strongly correlated dislocation structure of extensive number density of dislocations reaching almost 1017 m–2. Mean coherent domain size was estimated using both whole powder pattern modelling and modified Williamson–Hall methods, which yielded 9.5 and 7.5 nm, respectively. Powder consolidation induced crystallite growth accompanied with restrained drop in dislocation density. The anisotropic strain broadening of bcc iron diffraction peaks was taken into account by incorporating the dislocation contrast factor, directly related to elastic constants of material and to the dislocation slip system.

ESTIMATION OF CRYSTALLITE SIZE, LATTICE PARAMETER, INTERNAL STRAIN AND CRYSTAL IMPURIFICATION OF NANOCRYSTALLINE Al3Ni20Bx ALLOY BY WILLIAMSON-HALL METHOD

Al3Ni20Bx alloys (0.06≤ x ≤0.12) nanocrystalline, AlNiB-NCys were synthesized by rapid solidification method in an arc-melt furnace or in an induction furnace. The effect of changing the addition ratio of boron on the crystallography, microstrural, crystal impurifications has been investigated for the Al3Ni20Bx ternary. The crystal structure of samples obtained using X-ray diffraction was examined. XRD analysis revealed that prepared samples have the polycrystalline nanometric face centered cubic structure. XRDLine profile analysis by Lorentzian and Gaussian distributions were used to study the microstructure and crystal imperfections of Al3Ni20Bx. Crystallite size and microstrain were estimated using Williamson-Hall plots for the major eight XRD peaks. The data obtained shows that when the metal content is increased, the lattice parameters and volume of unit cell are increased linearly with boron concentration increase. This behavior is believed to be associated with an increase in content B by up to 11% that is entered into the unit cell of the Al3Ni20Bx system.

Optical, Structural, and Crystal Defects Characterizations of Dip Synthesized (Fe-Ni) Co-Doped ZnO Thin Films.

Sol-gel technique is used to synthesize as-grown zinc oxide (ZnO) and iron-nickel (Fe-Ni) co-doped ZnO thin films deposited on glass substrates using dip coating technique. The structural properties and crystal imperfections of as-prepared thin films are investigated. We performed the structural analysis of films using X-ray diffraction (XRD). The XRD analysis reveal that the as-prepared films exhibit wurtzite structure. Furthermore, XRD-line profile analysis is performed to study the correlation between structural properties and imperfections of the nanocomposite thin films. The crystallite size and microstrains parameters are predicted using the Williamson–Hall method. We found that the crystallites size increases as the co-doped (Fe-Ni) concentration is increased. However, microstrains of the nanocomposite films decreases as (Fe-Ni) concentration is increased. The optical properties of the (Fe-Ni) co-doped nanocomposite films are investigated by performing UV-Vis (250 nm–700 nm) spectrophotometer measurements. We found that as the (Fe-Ni) concentration level is steadily increased, transmittance of the undoped ZnO thin films is decreased. Remarkably, refractive index of undoped ZnO thin films is found to exhibit values extending from 1.55 to1.88 that would increase as (Fe-Ni) concentration is increased.

Modification of structural and magnetic properties of Co[formula omitted]Ni[formula omitted]Fe2O4 nanoparticles embedded Polyvinylidene Fluoride nanofiber membrane via electrospinning method

Ferrite nanoparticles have garnered significant attention due to their remarkable ferromagnetic properties. However, the functionality of the ferrite nanoparticles can be enhanced with the development of nanofiber membranes. This helps to control the surface, structural and magnetic properties of the composite nanofiber membrane. Herein, we report the fabrication of novel nanofiber membrane containing Co0.5Ni0.5Fe2O4-Polyvinylidene Fluoride (PVDF) via electrospinning method. The Co0.5Ni0.5Fe2O4 nanoparticles were synthesized with the help of sol–gel combustion method. Investigations on the effect of Co0.5Ni0.5Fe2O4 nanoparticles embedded within PVDF polymer nanofiber membrane on structural, morphological and magnetic properties are discussed. XRD line profile analysis revealed cubic spinel structure of the Co0.5Ni0.5Fe2O4 nanoparticles To determine the crystallite size of the samples; Scherrer, Williamson–Hall (W–H), and Size-Strain plot (SSP) were carried out with the help of XRD spectra. The crystallite size of the nanoparticles reduced as they were embedded within PVDF polymer. FTIR studies confirmed that the presence of Co0.5Ni0.5Fe2O4 pristine nanoparticles within the polymeric nanofiber membrane was accountable for the enhanced β-phase bands which makes a significant effect on the ferroelectric properties of the nanofiber membrane. In addition, the VSM technique was used to study the ferromagnetic properties. The enhanced remnant magnetization and saturation magnetization of the nanoparticles was responsible for magnetic nature of the non-magnetic polymer PVDF.

Impact of Co2+ Substitution on Microstructure and Magnetic Properties of CoxZn1-xFe2O4 Nanoparticles.

In the present work, we synthesized CoxZn1-xFe2O4 spinel ferrite nanoparticles (x= 0, 0.1, 0.2, 0.3 and 0.4) via the precipitation and hydrothermal-joint method. Structural parameters were cross-verified using X-ray powder diffraction (XRPD) and electron microscopy-based techniques. The magnetic parameters were determined by means of vibrating sample magnetometry. The as-synthesized CoxZn1-xFe2O4 nanoparticles exhibit high phase purity with a single-phase cubic spinel-type structure of Zn-ferrite. The microstructural parameters of the samples were estimated by XRD line profile analysis using the Williamson–Hall approach. The calculated grain sizes from XRPD analysis for the synthesized samples ranged from 8.3 to 11.4 nm. The electron microscopy analysis revealed that the constituents of all powder samples are spherical nanoparticles with proportions highly dependent on the Co doping ratio. The CoxZn1-xFe2O4 spinel ferrite system exhibits paramagnetic, superparamagnetic and weak ferromagnetic behavior at room temperature depending on the Co2+ doping ratio, while ferromagnetic ordering with a clear hysteresis loop is observed at low temperatures (5K). We concluded that replacing Zn2+ ions with Co2+ ions changes both the structural and magnetic properties of ZnFe2O4 nanoparticles.

Characterization of Dislocation Evolution in Cyclically Loaded Austenitic and Ferritic Stainless Steels via XRD Line-profile Analysis

Dislocations in austenitic and ferritic stainless steels (SSs) under cyclic loading were quantitatively evaluated via X-ray diffraction line-profile analysis to determine the relationship between the dislocation density and low-cycle fatigue (LCF) life in both SSs. The dislocation density of the austenitic and ferritic SSs varied linearly with respect to the LCF life in a double-logarithmic graph, with different slopes of the line. The dislocation density normalized by the maximum work hardening for both SSs exhibited a log–log linear relationship with the LCF life. The fraction of screw dislocations in the ferritic SS decreased with decreasing LCF life owing to the easy cross-slip of dislocations. Because of the difficulty of the cross-slip of dislocations in the austenitic SS, the fraction of screw dislocations remained almost constant throughout the LCF life. Analysis of the crystallite size and the dislocation arrangement with respect to the dislocation density under tensile and cyclic loading revealed that the dislocation arrangement for cyclic loading was smaller than that for tensile loading. Thus, the dislocation arrangement was related to the cyclic loading. In the plot of the dislocation evolution versus the number of cycles, two stages were observed in the variation of the dislocation characteristics for both SSs. In the first stage, the dislocation density increased, and the crystallite size decreased. The dislocation arrangement parameter of the ferritic and austenitic SS decreased and remained the same, respectively, in the first stage. In the second stage, the dislocation density, dislocation arrangement parameter, and crystallite size remained constant.

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.

Thickness dependent correlation between structural and optical properties of textured CdSe thin film

Nano-crystalline CdSe thin films of different thicknesses under sub-micron range were deposited on glass substrate via thermal evaporation route. A gradual deterioration in film crystallinity confirmed by XRD line profile analysis has been accompanied by a reduction in Cd to Se molar ratio as the film thickness decreases. A coordinated microstructural and crystallographic orientation distribution analysis explicitly demonstrated that CdSe tends to grow in nano-sized columns with hexagonal c-axis parallel to its growth direction on glass substrate. A thickness dependence of structural evolution was discussed in terms of aspect ratio of the columnar structure and dispersion in orientation of hexagonal (002) basal plane. The variation in the spectra of optical constants [n(λ), k(λ)] obtained from Swanepoel envelop method was interpreted in terms of crystallographic defects arising from stoichiometric disorder which was also accounted for the observed thickness dependent shifts in band gap and valence band split energy. The bathochromic shifts in dielectric and energy loss functions, optical conductivity, skin depth and cut-off energy were discussed in detail along with the variations in their spectral shapes in connection with the dispersion in the real and imaginary parts of complex refractive index, which might shed a new light upon holistic comprehension of thickness dependent optical properties of other chalcogenide semiconducting thin films.

Structure–property relation in HPMC:CoCl2 polymer composites using functional data analysis

Cobalt chloride doped HPMC polymer composites were characterized using various analytical studies. This includes, X-ray diffraction, conductivity, dielectric properties, mechanical strength and UV/Vis spectroscopy. These tests have been carried out to understand the changes in physical parameters of these composites, as an influence of doped CoCl2. Electrical conductivity, Impedance, dielectric loss and tensile strength of these films have been related with the microstructural parameters which are derived from the XRD line profile analysis. To efficiently state the structure dependence of these physical parameters, we have made use of Functional Data Analysis to validate such relation between the parameters. This study can be extended over any set of polymer composites to estimate the variations and dependency of structure on other physical parameters. Further, the study reveals that, cobalt chloride can be used as an effective dopant to modify conductivity in a non-conductive polymer.

Characterization of structural changes of mechanically activated natural pyrite using XRD line profile analysis

In the present study, the X-ray diffraction line profile analysis was used for the characterization of structural changes in mechanically activated pyrite by a planetary ball mill. Applying the Williamson-Hall integral breadth and Warren-Averbach methods, comprehensive investigations were carried out on the XRD patterns in order to separate the crystallite size and microstrain contributions in XRD broadened patterns. The analysis of XRD patterns of mechanically activated pyrite indicated that no phase transformation occurred during milling operation. The results revealed that crystallite size and microstrain decreased and increased, respectively, during mechanical activation process. Volume weighted crystallite size (Dv), surface weighted crystallite size (Ds), strain (ε) and root mean square strain (RMSS) changed from 316nm, 103.6nm, 0.05% and 0.04% in initial pyrite to 57.73nm, 25.1nm, 0.224% and 0.117%, respectively, in mechanically activated pyrite for 100min. In addition, the lattice parameter of mechanically activated pyrite increased as a function of milling time, implying that pyrite lattice volumes were expanded probably due to vacancy formation. Regarding to shape parameter study, the crystallite size broadening portion is more than the strain broadening portion on the broadened peaks in the XRD patterns of mechanically activated pyrite. This may be related to the fracture toughness of pyrite lattice, implying that pyrite structure is refined mainly by decreasing crystallite size rather than lattice strain. From surface area and particle size analysis, it can be confirmed that the agglomeration begins after 50min mechanical activation. The X-ray amorphization degree increases to about 70% after 100min intensive milling, reflecting the refractory nature of pyrite.

XRD Characterization of Microstructural Evolution During Mechanical Alloying of W-20 wt%Mo

The present paper reports a study on the micro- structural evolution during mechanical alloying of W-20 wt%Mo using XRD line profile analysis. The W-20wt%Mo powder blends were ball milled using Fritsch Pulverisette P-5 high energy ball mill for varying milling time (0, 5, 10, 15, 20 h) at 300 rpm with 10:1 and 2:1 ball to powder weight ratio. The crystallite size and lattice strain were calculated using Langford method ('average' Williamson-Hall Plot). The precision lattice parameter calculation was done using Nelson-Riley method. The effect of milling on alloying behaviour has been investigated using change in relative integrated intensity ratios (IMo/IW/W(Mo)) of (211) XRD peak. There was complete alloying in case of 10:1 ball to powder weight ratio, whereas half of the Mo (*10 % Mo) was alloyed with 2:1 ball to powder weight ratio. The paper also discusses the applicability of the criteria based on lattice parameter change (peak shift) for alloying behaviour during mechanical milling.

Microstructure and dislocation density evolutions in MgAlZn alloy processed by severe plastic deformation

Commercial MgAlZn alloy AZ31 was processed by hot extrusion and equal channel angular pressing (ECAP) known as EX-ECAP. Microstructure and defect structure evolution with strain due to ECAP were investigated by TEM, positron annihilation spectroscopy (PAS), and X-ray diffraction. Significant grain refinement was obtained by EX-ECAP. In the extruded condition relatively low density of dislocations was determined by PAS. Sharp increase of dislocation density occurred during the first two passes of ECAP, followed by the saturation and even a decline manifesting the dynamic recovery at higher strains. XRD line profile analysis confirmed the results of PAS with slightly higher values of dislocation densities in individual conditions. Detailed analysis of contrast factors allows to determine the type of dislocations and to draw conclusions about slip activation and its variations with strain. The influence of microstructure evolution on mechanical properties is discussed.

The generation of toxic reactive oxygen species (ROS) from mechanically activated sulphide concentrates and its effect on thermophilic bioleaching

Two types of laboratory mills, planetary and vibratory, were used to activate sulphide mineral concentrates mechanically before thermophilic (bio)leaching. These samples were analysed in terms of particle size, surface area, density, SEM, XRD line profile analysis and reactivity. The product particle size distributions indicated different particle breakage mechanisms of the two mills. The surface area for pyrite milled with the planetary mill was three fold that milled in the vibratory mill for the same length of time. Planetary milled samples showed lower densities, up to 4% less for pyrite samples, compared to vibratory milled samples. Particle surface oxidation, observed by SEM, occurred post milling. Surface oxidation products were more prevalent with planetary milled sulphide samples. XRD line profile analysis showed more line broadening effects with the planetary mill. This indicated that more bulk particle-related structural defects were present in the planetary milled samples. The reactivity in acidic solution was measured in terms of the generation of toxic reactive oxygen species (ROS): hydrogen peroxide and hydroxyl radicals. The ROS generation from milled sulphides, normalised to constant surface area loading, increased with increased mechanical activation. The planetary milled samples generated greater ROS per sample surface area than vibratory milled samples, more than 4-fold for pyrite after 60 min of milling. Increased ROS generation was postulated to result from increased surface area defects, solubilisation of iron oxidation products and bulk particle-related defects. The effect of mechanical activation on performance on thermophilic leaching and bioleaching tests was investigated using milled samples at 2% (w/v) pulp density. Short mill times improved leach rates from both mills, up to 7-fold cf. unactivated feed leach rates. Poor bioleaching performance resulted following long periods of mechanical activation (20–60 min). Pyrite and chalcopyrite bioleaching performance decreased dramatically above surface area loadings of 25 and 125 m 2/L respectively. Planetary milled samples were less amenable to bioleaching. For pyrite milled for 20 and 60 min and chalcopyrite milled for 40 min, no viable cells were observed following inoculation via fluorescence microscopy, suggesting culture death supported by compromised ferrous iron oxidation. The generation of ROS was postulated to cause poor bioleaching performance under these conditions.

Determination of Nanocrystalline Fe<sub>80</sub>Cr<sub>20</sub> Powder Based Alloys Using Williamson-Hall Method

The aim of this study is to determine the nanocrystalline size by using Williamson-Hall method of Fe80Cr20 powder which prepared by mechanical alloying process. X-rays diffraction line profile analysis was adopted to analyze the crystallite size and microstrains of Fe80Cr20 alloys powder. Transmission Electron Microscopy (TEM) was used to examine the microstructure morphology of the nanosized of Fe80Cr20 alloys. The crystallite size, microstrain, and lattice parameters were estimated by Williamson–Hall plot. The results showed that the mechanical alloying processes resulted the final product in nanocrystalline size range (below 12 nm) which confirmed by TEM observation and XRD line profile analysis.

Characterization of aging behavior of precipitates and dislocations in copper-based alloys

The growth of precipitates in a deformed Cu–Ni–Si alloy with an aging treatment and the rearrangement of dislocations were investigated using small-angle X-ray scattering method and XRD line-profile analysis. The small-angle X-ray scattering method was used for characterizing the growth behavior of the precipitates. The results showed that the precipitates grew gradually to a few nanometers in radius when aged under the condition that the alloy exhibited a maximum of the hardness due to precipitation hardening. The growth rate rose from the onset of the overaging, where the hardness started to decrease. The line-profile analysis of copper-based alloy diffraction peaks using modified Williamson–Hall and modified Warren–Averbach procedures yielded a variation in the dislocation densities of the alloy as a function of the aging time. The dislocation density of the alloy before the aging treatment was estimated to be 1.7×1015 m−2 and its high value was held up to the peak-aging time. With the onset of the overaging, however, the dislocation density distinctly decreased by about 1 order of magnitude indicating that a large amount of the dislocations rearranged to release the alloy from the high dislocation-density state. The results suggest that the massive rearrangement of dislocations was accompanied with coarsening of the precipitates.