scholarly journals Deformation Induced Soft and Hard Lath Packets Enhance Ductility in Martensitic Steels

Crystals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 373 ◽  
Author(s):  
Éva Ódor ◽  
Bertalan Jóni ◽  
Gábor Ribárik ◽  
Nguyen Quang Chinh ◽  
Tamás Ungár ◽  
...  
Keyword(s):  
Tensile Deformation ◽  
Profile Analysis ◽  
High Strength ◽  
Line Profile Analysis ◽  
Martensitic Steels ◽  
Hardness Tests ◽  
Dislocation Densities ◽  
Fast Cooling ◽  
Composite Microstructure ◽  
Coherency Strains

Martensitic steels are widely used structural materials with outstanding mechanical properties. Their high strength is provided by the non-diffusional phase transformation of fcc γ into thin lamellar bcc plates during fast cooling. Coherency strains between the fcc and bcc lamellae induce large dislocation densities in the range of 1016 m−2, well above the densities attainable by conventional plastic deformation. Using high resolution X-ray line profile analysis, scanning electron microscopy, and hardness tests we show that during tensile deformation when the active Burgers vectors are within the lath plane the lath-packets work soften. On the contrary, when the active Burgers vectors are oblique to the lath-plane the lath-packets work harden. The softening and hardening processes in the differently oriented lath-packets produce a composite of hard and soft components on the length scale of lath-packet size. The stress–strain response of the alloy is discussed in terms of the different mean free paths and the different annihilation lengths of dislocations in the softened and hardened lath-packets. The relatively good ductility is shown to be produced by the composite microstructure induced by plastic strain.

Dislocation densities and prevailing slip-system types determined by X-ray line profile analysis in a textured AZ31 magnesium alloy deformed at different temperatures

2013 ◽  
Vol 46 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Bertalan Jóni ◽  
Talal Al-Samman ◽  
Sandip Ghosh Chowdhury ◽  
Gábor Csiszár ◽  
Tamás Ungár
Keyword(s):  
Magnesium Alloy ◽  
Tensile Deformation ◽  
Profile Analysis ◽  
High Angular Resolution ◽  
Line Profile Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dislocation Densities ◽  
Different Temperatures ◽  
Diffraction Patterns

Tension experiments were carried out at room temperature, 473 K and 673 K on AZ31-type extruded magnesium alloy samples. The tensile deformation has almost no effect on the typical extrusion texture at any of the investigated temperatures. X-ray diffraction patterns provided by a high-angular-resolution diffractometer were analyzed for the dislocation density and slip activity after deformation to fracture. The diffraction peaks were sorted into two groups corresponding either to the major or to the random texture components in the specimen. The two groups of reflections were evaluated simultaneously as if the two texture components were two different phases. The dislocation densities in the major texture components are found to be always larger than those in the randomly oriented grain populations. The overwhelming fraction of dislocations prevailing in the samples is found to be of 〈a〉 type, with a smaller fraction of 〈c + a〉-type dislocations. The fraction of 〈c〉-type dislocations is always obtained to be zero within experimental error.

Dislocation Densities in Dispersion-Strengthened Copper with Aluminum Oxide from X-Ray Line Profile Analysis

2018 ◽  
Vol 941 ◽  
pp. 2024-2029
Author(s):  
Mutsumi Sano ◽  
Sunao Takahashi ◽  
Atsuo Watanabe ◽  
Ayumi Shiro ◽  
Takahisa Shobu ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Aluminum Oxide ◽  
Ambient Temperature ◽  
Line Profile ◽  
Profile Analysis ◽  
Compressive Strain ◽  
Line Profile Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dislocation Densities

Dislocation densities of dispersion-strengthened copper with aluminum oxide, namely GlidCop were evaluated employing the X-ray line profile analysis using the modified Williamson-Hall and modified Warren-Averbach method. X-ray diffraction profiles for GldCop samples with compressive strains applied at ambient temperature were measured with synchrotron radiation. The dislocation densities of GlidCop with compressive strain ranging from 0 – 2.7 % were on the order of 1.5×1014 – 6.6×1014 m-2.

Dislocation densities and crystallite size distributions in nanocrystalline ball-milled fluorides,MF2(M= Ca, Sr, Ba and Cd), determined by X-ray diffraction line-profile analysis

2005 ◽  
Vol 38 (6) ◽  
pp. 912-926 ◽  
Author(s):  
G. Ribárik ◽  
N. Audebrand ◽  
H. Palancher ◽  
T. Ungár ◽  
D. Louër
Keyword(s):  
Crystallite Size ◽  
Line Profile ◽  
Interference Effect ◽  
Profile Analysis ◽  
Line Profile Analysis ◽  
Size Distributions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Line Profile ◽  
Dislocation Densities

The dislocation densities and crystallite size distributions in ball-milled fluorides,MF2(M= Ca, Sr, Ba and Cd), of the fluorite structure type have been determined as a function of milling time by X-ray diffraction line-profile analysis. The treatment has been based on the concept of dislocation contrast to explain strain anisotropy by means of the modified Williamson–Hall and Warren–Averbach approaches and a whole-profile fitting method using physically based functions. In most cases, the measured and calculated patterns are in perfect agreement; however, in some specific cases, the first few measured profiles appear to be narrower than the calculated ones. This discrepancy is interpreted as the result of an interference effect similar to that described by Rafaja, Klemm, Schreiber, Knapp & Kužel [J. Appl. Cryst.(2004),37, 613–620]. By taking into account and correcting for this interference effect, the microstructure of ball-milled fluorides is determined in terms of dislocation structure and size distributions of coherent domains. A weak coalescence of the crystallites is observed at longer milling periods. An incubation period in the evolution of microstrains is in correlation with the homologous temperatures of the fluorides.

scholarly journals In situ synchrotron X-ray diffraction line-profile analysis of additively manufactured Ti−6Al−4V alloy under tensile deformation

2020 ◽  
Vol 321 ◽  
pp. 03026
Author(s):  
K. Yamanaka ◽  
A. Kuroda ◽  
M. Ito ◽  
M. Mori ◽  
T. Shobu ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Line Profile ◽  
Tensile Deformation ◽  
Profile Analysis ◽  
High Energy ◽  
Line Profile Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase

In this study, the tensile deformation behavior of an electron beam melted Ti−6Al−4V alloy was examined by in situ X-ray diffraction (XRD) line-profile analysis. The as-built Ti−6Al−4V alloy specimen showed a fine acicular microstructure that was produced through the decomposition of the α′-martensite during the post-melt exposure to high temperatures. Using high-energy synchrotron radiation, XRD line-profile analysis was successfully applied for examining the evolution of dislocation structures not only in the α-matrix but also in the nanosized, low-fraction β-phase precipitates located at the interfaces between the α-laths. The results indicated that the dislocation density was initially higher in the β-phase and an increased dislocation density with increasing applied tensile strain was quantitatively captured in each constitutive phase. It can be thus concluded that the EBM Ti−6Al−4V alloy undergoes a cooperative plastic deformation between the constituent phases in the duplex microstructure. These results also suggested that XRD line-profile analysis combined with highenergy synchrotron XRD measurements can be utilized as a powerful tool for characterizing duplex microstructures in titanium alloys.

scholarly journals Microstructure Characterization in Individual Texture Components by X-Ray Line Profile Analysis: Principles of the X-TEX Method and Practical Application to Tensile-Deformed Textured Ti

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 691
Author(s):  
Bertalan Jóni ◽  
Éva Ódor ◽  
Mia Maric ◽  
Wolfgang Pantleon ◽  
Tamás Ungár
Keyword(s):  
Line Profile ◽  
Profile Analysis ◽  
Subgrain Size ◽  
Pure Titanium ◽  
Evaluation Procedure ◽  
Line Profile Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dislocation Densities ◽  
Diffraction Peaks

A novel X-ray diffraction-based method and computer program X-TEX has been developed to determine the microstructure in individual texture components of polycrystalline, textured materials. Two different approaches are presented. In the first one, based on the texture of the specimen, the X-TEX software provides optimized specimen orientations for X-ray diffraction experiments in which diffraction peaks consist of intensity contributions stemming from grain populations of separate texture components in the specimen. Texture-specific diffraction patterns can be created by putting such peaks together from different measurements into an artificial pattern for each texture component. In the second one, the X-TEX software can determine the intensity contributions of different texture components to diffraction peaks measured in a particular sample orientation. According to this, peaks belonging mainly to one of the present texture components are identified and grouped into the same quasi-phase during the evaluation procedure. The X-TEX method was applied and tested on tensile-deformed, textured, commercially pure titanium samples. The patterns were evaluated by the convolutional multiple whole profile (CMWP) procedure of line profile analysis for dislocation densities, dipole character, slip systems and subgrain size for three different texture components of the Ti specimens. Significant differences were found in the microstructure evolution in the two major and the random texture components. The dislocation densities were discussed by the Taylor model of work hardening.

scholarly journals Precipitation Microstructure of Ultrafine-Grained Al-Zn-Mg Alloys Processed by Severe Plastic Deformation

2007 ◽  
Vol 537-538 ◽  
pp. 169-176 ◽  
Author(s):  
Jenő Gubicza ◽  
I. Schiller ◽  
Nguyen Q. Chinh ◽  
Judit Illy
Keyword(s):  
Profile Analysis ◽  
High Strength ◽  
Precipitation Process ◽  
Line Profile Analysis ◽  
X Ray Diffraction ◽  
Diffraction Line Profile ◽  
Angular Pressing ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Precipitation Microstructure

Supersaturated Al-4.8Zn-1.2Mg-0.14Zr and Al-5.7Zn-1.9Mg-0.35Cu (wt.%) alloys were processed by Equal-Channel Angular Pressing (ECAP) at 200°C. The crystallite size distribution and the characteristic parameters of the dislocation structure of both Al matrix and precipitates were determined by X-ray diffraction line profile analysis, which has been complemented by transmission electron microscopy (TEM) observations. Results of these investigations show that the bulk ultrafine-grained microstructure with high dislocation density produced by ECAP has strong influence on the precipitation process, resulting in high strength in both alloys.

Nanostructures and Microhardness in Al and Al–Mg Alloys Subjected to SPD

2008 ◽  
Vol 604-605 ◽  
pp. 179-185 ◽  
Author(s):  
Hans Jørgen Roven ◽  
M. Liu ◽  
Maxim Yu. Murashkin ◽  
Ruslan Valiev ◽  
A.R. Kilmametov ◽  
...  
Keyword(s):  
High Resolution ◽  
High Pressure Torsion ◽  
Profile Analysis ◽  
High Hardness ◽  
Mg Alloys ◽  
Line Profile Analysis ◽  
Dislocation Densities ◽  
Average Grain Size ◽  
Hardness Values ◽  
Al Mg Alloys

Nanostructures and microhardness of a commercial purity Al, three binary Al–Mg alloys and a commercial AA5182 alloy subjected to high pressure torsion (HPT) at room temperature were comparatively investigated using high-resolution transmission electron microscopy, X-ray diffraction (XRD) and high-resolution XRD line profile analysis. The hardness values of HPT samples are twice to three times larger than that of the undeformed counterparts. Grain sizes measured by XRD are in the range 10–200 nm with typical average values ranging from 46 to 120 nm. The hardness values and the dislocation densities increased, whereas, the average grain size decreased significantly with increasing Mg contents. Typical dislocation densities are in the range 1.7 × 1014 m-2 – 2.3 × 1015 m-2. However, local densities in grain boundary and triple junction areas might be as high as 1017 m-2. The strengthening mechanisms contributing to high hardness may primarily be attributed to the cooperative interactions of high dislocation densities, grain boundaries and planar interfaces.

Dislocation Densities, Slip-System Types and Burgers Vector Populationsinhexagonal and Cubiccrystalsfrom X-Ray Line Profile Analysis

2011 ◽  
Vol 702-703 ◽  
pp. 479-484
Author(s):  
Tamás Ungár
Keyword(s):  
Line Profile ◽  
Profile Analysis ◽  
Polycrystalline Materials ◽  
Line Profile Analysis ◽  
X Ray Diffraction ◽  
Burgers Vector ◽  
X Ray ◽  
Diffraction Line Profile ◽  
Vector Population ◽  
Dislocation Densities

X-ray diffraction line profile analysis can be carried out on the hkl planes corresponding to the same texture component or the same crystallographic orientation fiber. It is shown that in textured polycrystalline materials or in thin films or multilayers X-ray line profiles measured on planes corresponding either to the main or the minor texture components can provide the Burgers vector population and dislocations densities in the different texture components separately. The experimental technique is outlined for textured specimens and the multiple convolutional whole profile method, i.e. the CMWP line profile analysis procedure, is presented for its capacity to determine the substructure pertaining to different texture components in textured samples.

scholarly journals Data-Driven Analysis of Neutron Diffraction Line Profiles: Application to Plastically Deformed Ta

2021 ◽  
Author(s):  
Aaron Tallman ◽  
Reeju Pokharel ◽  
Darshan Bamney ◽  
Douglas Spearot ◽  
Bjorn Clausen ◽  
...  
Keyword(s):  
Profile Analysis ◽  
Constitutive Models ◽  
Gaussian Process Regression ◽  
Dislocation Dynamics ◽  
Diffraction Line ◽  
Data Driven ◽  
Analytical Models ◽  
Line Profile Analysis ◽  
Line Profiles ◽  
Dislocation Densities

Abstract Non-destructive evaluation of plastically deformed metals, particularly diffraction line profile analysis (DLPA), is valuable both to estimate dislocation densities and arrangements and to validate microstructure-aware constitutive models. To date, the interpretation of whole line diffraction profiles relies on the use of semi-analytical models such as the extended convolutional multiple whole profile (eCMWP) method. This study introduces and validates two data-driven DLPA models to extract dislocation densities from experimentally gathered whole line diffraction profiles. Using two distinct virtual diffraction models accounting for both strain and instrument induced broadening, a database of virtual diffraction whole line profiles of Ta single crystals is generated using discrete dislocation dynamics. The databases are mined to create Gaussian process regression-based surrogate models, allowing dislocation densities to be extracted from experimental profiles. The method is validated against 11 experimentally gathered whole line diffraction profiles from plastically deformed Ta polycrystals. The newly proposed model predicts dislocation densities consistent with estimates from eCMWP. Advantageously, this data driven LPA model can distinguish broadening originating from the instrument and from the dislocation content even at low dislocation densities. Finally, the data-driven model is used to explore the effect of heterogeneous dislocation densities in microstructures containing grains, which may lead to more accurate data-driven predictions of dislocation density in plastically deformed polycrystals.

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