Metals

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186 KiB

Open AccessEditorial

Metals Challenged by Neutron and Synchrotron Radiation

by Klaus-Dieter Liss

Metals 2017, 7(7), 266; https://doi.org/10.3390/met7070266 - 11 Jul 2017

Cited by 13 | Viewed by 4302

Abstract

In the past one and a half decades, neutron and synchrotron radiation techniques have come to the forefront as an excellent set of tools for the wider investigation of material structures and properties [1,2], becoming available to a large user community.[...] Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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Research

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6085 KiB

Open AccessArticle

Hydrostatic Compression Behavior and High-Pressure Stabilized β-Phase in γ-Based Titanium Aluminide Intermetallics

by Klaus-Dieter Liss, Ken-Ichi Funakoshi, Rian Johannes Dippenaar, Yuji Higo, Ayumi Shiro, Mark Reid, Hiroshi Suzuki, Takahisa Shobu and Koichi Akita

Metals 2016, 6(7), 165; https://doi.org/10.3390/met6070165 - 15 Jul 2016

Cited by 21 | Viewed by 7082 | Correction

Abstract

Titanium aluminides find application in modern light-weight, high-temperature turbines, such as aircraft engines, but suffer from poor plasticity during manufacturing and processing. Huge forging presses enable materials processing in the 10-GPa range, and hence, it is necessary to investigate the phase diagrams of [...] Read more.

Titanium aluminides find application in modern light-weight, high-temperature turbines, such as aircraft engines, but suffer from poor plasticity during manufacturing and processing. Huge forging presses enable materials processing in the 10-GPa range, and hence, it is necessary to investigate the phase diagrams of candidate materials under these extreme conditions. Here, we report on an in situ synchrotron X-ray diffraction study in a large-volume press of a modern (α₂ + γ) two-phase material, Ti-45Al-7.5Nb-0.25C, under pressures up to 9.6 GPa and temperatures up to 1686 K. At room temperature, the volume response to pressure is accommodated by the transformation γ → α₂, rather than volumetric strain, expressed by the apparently high bulk moduli of both constituent phases. Crystallographic aspects, specifically lattice strain and atomic order, are discussed in detail. It is interesting to note that this transformation takes place despite an increase in atomic volume, which is due to the high ordering energy of γ. Upon heating under high pressure, both the eutectoid and γ-solvus transition temperatures are elevated, and a third, cubic β-phase is stabilized above 1350 K. Earlier research has shown that this β-phase is very ductile during plastic deformation, essential in near-conventional forging processes. Here, we were able to identify an ideal processing window for near-conventional forging, while the presence of the detrimental β-phase is not present under operating conditions. Novel processing routes can be defined from these findings. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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3866 KiB

Open AccessFeature PaperArticle

Hydrogen Absorption in Metal Thin Films and Heterostructures Investigated in Situ with Neutron and X-ray Scattering

by Sara J. Callori, Christine Rehm, Grace L. Causer, Mikhail Kostylev and Frank Klose

Metals 2016, 6(6), 125; https://doi.org/10.3390/met6060125 - 24 May 2016

Cited by 21 | Viewed by 8510

Abstract

Due to hydrogen possessing a relatively large neutron scattering length, hydrogen absorption and desorption behaviors in metal thin films can straightforwardly be investigated by neutron reflectometry. However, to further elucidate the chemical structure of the hydrogen absorbing materials, complementary techniques such as high [...] Read more.

Due to hydrogen possessing a relatively large neutron scattering length, hydrogen absorption and desorption behaviors in metal thin films can straightforwardly be investigated by neutron reflectometry. However, to further elucidate the chemical structure of the hydrogen absorbing materials, complementary techniques such as high resolution X-ray reflectometry and diffraction remain important too. Examples of work on such systems include Nb- and Pd-based multilayers, where Nb and Pd both have strong affinity to hydrogen. W/Nb and Fe/Nb multilayers were measured in situ with unpolarized and polarized neutron reflectometry under hydrogen gas charging conditions. The gas-pressure/hydrogen-concentration dependence, the hydrogen-induced macroscopic film swelling as well as the increase in crystal lattice plane distances of the films were determined. Ferromagnetic-Co/Pd multilayers were studied with polarized neutron reflectometry and in situ ferromagnetic resonance measurements to understand the effect of hydrogen absorption on the magnetic properties of the system. This electronic effect enables a novel approach for hydrogen sensing using a magnetic readout scheme. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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2172 KiB

Open AccessFeature PaperArticle

Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

by Darren J. Goossens

Metals 2016, 6(2), 33; https://doi.org/10.3390/met6020033 - 4 Feb 2016

Cited by 2 | Viewed by 5567

Abstract

Single-crystal diffuse scattering (SCDS) reveals detailed structural insights into materials. In particular, it is sensitive to two-body correlations, whereas traditional Bragg peak-based methods are sensitive to single-body correlations. This means that diffuse scattering is sensitive to ordering that persists for just a few [...] Read more.

Single-crystal diffuse scattering (SCDS) reveals detailed structural insights into materials. In particular, it is sensitive to two-body correlations, whereas traditional Bragg peak-based methods are sensitive to single-body correlations. This means that diffuse scattering is sensitive to ordering that persists for just a few unit cells: nanoscale order, sometimes referred to as “local structure”, which is often crucial for understanding a material and its function. Metals and alloys were early candidates for SCDS studies because of the availability of large single crystals. While great progress has been made in areas like ab initio modelling and molecular dynamics, a place remains for Monte Carlo modelling of model crystals because of its ability to model very large systems; important when correlations are relatively long (though still finite) in range. This paper briefly outlines, and gives examples of, some Monte Carlo methods appropriate for the modelling of SCDS from metallic compounds, and considers data collection as well as analysis. Even if the interest in the material is driven primarily by magnetism or transport behaviour, an understanding of the local structure can underpin such studies and give an indication of nanoscale inhomogeneity. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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2257 KiB

Open AccessFeature PaperArticle

Probing Interfaces in Metals Using Neutron Reflectometry

by Michael J. Demkowicz and Jaroslaw Majewski

Metals 2016, 6(1), 20; https://doi.org/10.3390/met6010020 - 20 Jan 2016

Cited by 8 | Viewed by 8390

Abstract

Solid-state interfaces play a major role in a variety of material properties. They are especially important in determining the behavior of nano-structured materials, such as metallic multilayers. However, interface structure and properties remain poorly understood, in part because the experimental toolbox for characterizing [...] Read more.

Solid-state interfaces play a major role in a variety of material properties. They are especially important in determining the behavior of nano-structured materials, such as metallic multilayers. However, interface structure and properties remain poorly understood, in part because the experimental toolbox for characterizing them is limited. Neutron reflectometry (NR) offers unique opportunities for studying interfaces in metals due to the high penetration depth of neutrons and the non-monotonic dependence of their scattering cross-sections on atomic numbers. We review the basic physics of NR and outline the advantages that this method offers for investigating interface behavior in metals, especially under extreme environments. We then present several example NR studies to illustrate these advantages and discuss avenues for expanding the use of NR within the metals community. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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1194 KiB

Open AccessArticle

Study on Sintering Mechanism of Stainless Steel Fiber Felts by X-ray Computed Tomography

by Jun Ma, Aijun Li and Huiping Tang

Metals 2016, 6(1), 18; https://doi.org/10.3390/met6010018 - 13 Jan 2016

Cited by 9 | Viewed by 5707

Abstract

The microstructure evolution of Fe-17 wt. % Cr-12 wt. % Ni-2 wt. % Mo stainless steel fiber felts during the fast sintering process was investigated by the synchrotron radiation X-ray computed tomography technique. The equation of dynamics of stable inter-fiber neck growth was [...] Read more.

The microstructure evolution of Fe-17 wt. % Cr-12 wt. % Ni-2 wt. % Mo stainless steel fiber felts during the fast sintering process was investigated by the synchrotron radiation X-ray computed tomography technique. The equation of dynamics of stable inter-fiber neck growth was established for the first time based on the geometry model of sintering joints of two fibers and Kucsynski’s two-sphere model. The specific evolutions of different kinds of sintering joints were observed in the three-dimensional images. The sintering mechanisms during sintering were proposed as plastic flow and grain boundary diffusion, the former leading to a quick growth of sintering joints. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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2228 KiB

Open AccessArticle

Deformation in Metallic Glasses Studied by Synchrotron X-Ray Diffraction

by Takeshi Egami, Yang Tong and Wojciech Dmowski

Metals 2016, 6(1), 22; https://doi.org/10.3390/met6010022 - 11 Jan 2016

Cited by 17 | Viewed by 6437

Abstract

High mechanical strength is one of the superior properties of metallic glasses which render them promising as a structural material. However, understanding the process of mechanical deformation in strongly disordered matter, such as metallic glass, is exceedingly difficult because even an effort to [...] Read more.

High mechanical strength is one of the superior properties of metallic glasses which render them promising as a structural material. However, understanding the process of mechanical deformation in strongly disordered matter, such as metallic glass, is exceedingly difficult because even an effort to describe the structure qualitatively is hampered by the absence of crystalline periodicity. In spite of such challenges, we demonstrate that high-energy synchrotron X-ray diffraction measurement under stress, using a two-dimensional detector coupled with the anisotropic pair-density function (PDF) analysis, has greatly facilitated the effort of unraveling complex atomic rearrangements involved in the elastic, anelastic, and plastic deformation of metallic glasses. Even though PDF only provides information on the correlation between two atoms and not on many-body correlations, which are often necessary in elucidating various properties, by using stress as means of exciting the system we can garner rich information on the nature of the atomic structure and local atomic rearrangements during deformation in glasses. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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1817 KiB

Open AccessArticle

Monitoring of Bainite Transformation Using in Situ Neutron Scattering

by Hikari Nishijima, Yo Tomota, Yuhua Su, Wu Gong and Jun-ichi Suzuki

Metals 2016, 6(1), 16; https://doi.org/10.3390/met6010016 - 9 Jan 2016

Cited by 8 | Viewed by 5166

Abstract

Bainite transformation behavior was monitored using simultaneous measurements of dilatometry and small angle neutron scattering (SANS). The volume fraction of bainitic ferrite was estimated from the SANS intensity, showing good agreement with the results of the dilatometry measurements. We propose a more advanced [...] Read more.

Bainite transformation behavior was monitored using simultaneous measurements of dilatometry and small angle neutron scattering (SANS). The volume fraction of bainitic ferrite was estimated from the SANS intensity, showing good agreement with the results of the dilatometry measurements. We propose a more advanced monitoring technique combining dilatometry, SANS and neutron diffraction. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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2782 KiB

Open AccessArticle

Investigation of Elastic Deformation Mechanism in As-Cast and Annealed Eutectic and Hypoeutectic Zr–Cu–Al Metallic Glasses by Multiscale Strain Analysis

by Hiroshi Suzuki, Rui Yamada, Shinki Tsubaki, Muneyuki Imafuku, Shigeo Sato, Tetsu Watanuki, Akihiko Machida and Junji Saida

Metals 2016, 6(1), 12; https://doi.org/10.3390/met6010012 - 5 Jan 2016

Cited by 4 | Viewed by 5082

Abstract

Elastic deformation behaviors of as-cast and annealed eutectic and hypoeutectic Zr–Cu–Al bulk metallic glasses (BMG) were investigated on a basis of different strain-scales, determined by X-ray scattering and the strain gauge. The microscopic strains determined by Direct-space method and Reciprocal-space method were compared [...] Read more.

Elastic deformation behaviors of as-cast and annealed eutectic and hypoeutectic Zr–Cu–Al bulk metallic glasses (BMG) were investigated on a basis of different strain-scales, determined by X-ray scattering and the strain gauge. The microscopic strains determined by Direct-space method and Reciprocal-space method were compared with the macroscopic strain measured by the strain gauge, and the difference in the deformation mechanism between eutectic and hypoeutectic Zr–Cu–Al BMGs was investigated by their correlation. The eutectic Zr₅₀Cu₄₀Al₁₀ BMG obtains more homogeneous microstructure by free-volume annihilation after annealing, improving a resistance to deformation but degrading ductility because of a decrease in the volume fraction of weakly-bonded regions with relatively high mobility. On the other hand, the as-cast hypoeutectic Zr₆₀Cu₃₀Al₁₀ BMG originally has homogeneous microstructure but loses its structural and elastic homogeneities because of nanocluster formation after annealing. Such structural changes by annealing might develop unique mechanical properties showing no degradations of ductility and toughness for the structural-relaxed hypoeutectic Zr₆₀Cu₃₀Al₁₀ BMGs. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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3770 KiB

Open AccessArticle

In situ Investigation of Titanium Powder Microwave Sintering by Synchrotron Radiation Computed Tomography

by Yu Xiao, Feng Xu, Xiaofang Hu, Yongcun Li, Wenchao Liu and Bo Dong

Metals 2016, 6(1), 9; https://doi.org/10.3390/met6010009 - 4 Jan 2016

Cited by 12 | Viewed by 5886

Abstract

In this study, synchrotron radiation computed tomography was applied to investigate the mechanisms of titanium powder microwave sintering in situ. On the basis of reconstructed images, we observed that the sintering described in this study differs from conventional sintering in terms of [...] Read more.

In this study, synchrotron radiation computed tomography was applied to investigate the mechanisms of titanium powder microwave sintering in situ. On the basis of reconstructed images, we observed that the sintering described in this study differs from conventional sintering in terms of particle smoothing, rounding, and short-term growth. Contacted particles were also isolated. The kinetic curves of sintering neck growth and particle surface area were obtained and compared with those of other microwave-sintered metals to examine the interaction mechanisms between mass and microwave fields. Results show that sintering neck growth accelerated from the intermediate period; however, this finding is inconsistent with that of aluminum powder microwave sintering described in previous work. The free surface areas of the particles were also quantitatively analyzed. In addition to the eddy current loss in metal particles, other heating mechanisms, including dielectric loss, interfacial polarization effect, and local plasma-activated sintering, contributed to sintering neck growth. Thermal and non-thermal effects possibly accelerated the sintering neck growth of titanium. This study provides a useful reference of further research on interaction mechanisms between mass and microwave fields during microwave sintering. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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902 KiB

Open AccessArticle

Forge-Hardened TiZr Null-Matrix Alloy for Neutron Scattering under Extreme Conditions

by Takuo Okuchi, Akinori Hoshikawa and Toru Ishigaki

Metals 2015, 5(4), 2340-2350; https://doi.org/10.3390/met5042340 - 9 Dec 2015

Cited by 9 | Viewed by 5621

Abstract

For neutron scattering research that is performed under extreme conditions, such as high static pressures, high-strength metals that are transparent to the neutron beam are required. The diffraction of the neutron beam by the metal, which follows Bragg’s law, can be completely removed [...] Read more.

For neutron scattering research that is performed under extreme conditions, such as high static pressures, high-strength metals that are transparent to the neutron beam are required. The diffraction of the neutron beam by the metal, which follows Bragg’s law, can be completely removed by alloying two metallic elements that have coherent scattering lengths with opposite signs. An alloy of Ti and Zr, which is known as a TiZr null-matrix alloy, is an ideal combination for such purposes. In this study, we increased the hardness of a TiZr null-matrix alloy via extensive mechanical deformation at high temperatures. We successfully used the resulting product in a high-pressure cell designed for high-static-pressure neutron scattering. This hardened TiZr null-matrix alloy may play a complementary role to normal TiZr alloy in future neutron scattering research under extreme conditions. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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1160 KiB

Open AccessFeature PaperArticle

In Situ High-Energy X-ray Diffraction during Hot-Forming of a Multiphase TiAl Alloy

by Andreas Stark, Marcus Rackel, Aristide Tchouaha Tankoua, Michael Oehring, Norbert Schell, Lars Lottermoser, Andreas Schreyer and Florian Pyczak

Metals 2015, 5(4), 2252-2265; https://doi.org/10.3390/met5042252 - 30 Nov 2015

Cited by 19 | Viewed by 7374

Abstract

Intermetallic γ-TiAl based alloys exhibit excellent high-temperature strength combined with low density. This makes them ideal candidates for replacing the twice as dense Ni base super-alloys, currently used in the medium temperature range (~700 °C) of industrial and aviation gas turbines. An important [...] Read more.

Intermetallic γ-TiAl based alloys exhibit excellent high-temperature strength combined with low density. This makes them ideal candidates for replacing the twice as dense Ni base super-alloys, currently used in the medium temperature range (~700 °C) of industrial and aviation gas turbines. An important step towards the serial production of TiAl parts is the development of suitable hot-forming processes. Thermo-mechanical treatments often result in mechanical anisotropy due to the formation of crystallographic textures. However, with conventional texture analysis techniques, their formation can only be studied after processing. In this study, in situ high-energy X-ray diffraction measurements with synchrotron radiation were performed during hot-forming. Thus, it was possible to record the evolution of the phase constitution as well as the formation of crystallographic texture of different phases directly during processing. Several process temperatures (1100 °C to 1300 °C) and deformation rates were investigated. Based on these experiments, a process window can be recommended which results in the formation of an optimal reduced texture. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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933 KiB

Open AccessArticle

Dynamic Strain Evolution around a Crack Tip under Steady- and Overloaded-Fatigue Conditions

by Soo Yeol Lee, E-Wen Huang, Wanchuck Woo, Cheol Yoon, Hobyung Chae and Soon-Gil Yoon

Metals 2015, 5(4), 2109-2118; https://doi.org/10.3390/met5042109 - 12 Nov 2015

Cited by 30 | Viewed by 5925

Abstract

We investigated the evolution of the strain fields around a fatigued crack tip between the steady- and overloaded-fatigue conditions using a nondestructive neutron diffraction technique. The two fatigued compact-tension specimens, with a different fatigue history but an identical applied stress intensity factor range, [...] Read more.

We investigated the evolution of the strain fields around a fatigued crack tip between the steady- and overloaded-fatigue conditions using a nondestructive neutron diffraction technique. The two fatigued compact-tension specimens, with a different fatigue history but an identical applied stress intensity factor range, were used for the direct comparison of the crack tip stress/strain distributions during in situ loading. While strains behind the crack tip in the steady-fatigued specimen are irrelevant to increasing applied load, the strains behind the crack tip in the overloaded-fatigued specimen evolve significantly under loading, leading to a lower driving force of fatigue crack growth. The results reveal the overload retardation mechanism and the correlation between crack tip stress distribution and fatigue crack growth rate. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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900 KiB

Open AccessArticle

Detecting Structural Features in Metallic Glass via Synchrotron Radiation Experiments Combined with Simulations

by Gu-Qing Guo, Shi-Yang Wu, Sheng Luo and Liang Yang

Metals 2015, 5(4), 2093-2108; https://doi.org/10.3390/met5042093 - 9 Nov 2015

Cited by 19 | Viewed by 7146

Abstract

Revealing the essential structural features of metallic glasses (MGs) will enhance the understanding of glass-forming mechanisms. In this work, a feasible scheme is provided where we performed the state-of-the-art synchrotron-radiation based experiments combined with simulations to investigate the microstructures of ZrCu amorphous compositions. [...] Read more.

Revealing the essential structural features of metallic glasses (MGs) will enhance the understanding of glass-forming mechanisms. In this work, a feasible scheme is provided where we performed the state-of-the-art synchrotron-radiation based experiments combined with simulations to investigate the microstructures of ZrCu amorphous compositions. It is revealed that in order to stabilize the amorphous state and optimize the topological and chemical distribution, besides the icosahedral or icosahedral-like clusters, other types of clusters also participate in the formation of the microstructure in MGs. This cluster-level co-existing feature may be popular in this class of glassy materials. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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710 KiB

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How Can Synchrotron Radiation Techniques Be Applied for Detecting Microstructures in Amorphous Alloys?

by Gu-Qing Guo, Shi-Yang Wu, Sheng Luo and Liang Yang

Metals 2015, 5(4), 2048-2057; https://doi.org/10.3390/met5042048 - 4 Nov 2015

Cited by 10 | Viewed by 4528

Abstract

In this work, how synchrotron radiation techniques can be applied for detecting the microstructure in metallic glass (MG) is studied. The unit cells are the basic structural units in crystals, though it has been suggested that the co-existence of various clusters may be [...] Read more.

In this work, how synchrotron radiation techniques can be applied for detecting the microstructure in metallic glass (MG) is studied. The unit cells are the basic structural units in crystals, though it has been suggested that the co-existence of various clusters may be the universal structural feature in MG. Therefore, it is a challenge to detect microstructures of MG even at the short-range scale by directly using synchrotron radiation techniques, such as X-ray diffraction and X-ray absorption methods. Here, a feasible scheme is developed where some state-of-the-art synchrotron radiation-based experiments can be combined with simulations to investigate the microstructure in MG. By studying a typical MG composition (Zr₇₀Pd₃₀), it is found that various clusters do co-exist in its microstructure, and icosahedral-like clusters are the popular structural units. This is the structural origin where there is precipitation of an icosahedral quasicrystalline phase prior to phase transformation from glass to crystal when heating Zr₇₀Pd₃₀ MG. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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761 KiB

Open AccessArticle

Resistance of Hydrogenated Titanium-Doped Diamond-Like Carbon Film to Hyperthermal Atomic Oxygen

by Kengo Kidena, Minami Endo, Hiroki Takamatsu, Masahito Niibe, Masahito Tagawa, Kumiko Yokota, Yuichi Furuyama, Keiji Komatsu, Hidetoshi Saitoh and Kazuhiro Kanda

Metals 2015, 5(4), 1957-1970; https://doi.org/10.3390/met5041957 - 23 Oct 2015

Cited by 6 | Viewed by 5207

Abstract

The effect of irradiation by a hyperthermal-atomic-oxygen beam on hydrogenated titanium-doped diamond-like carbon (hydrogenated Ti-DLC) films, applied as a solid lubricant for equipment used in low-earth orbit was investigated. Unlike the film thickness of hydrogenated non-doped DLC films, that of hydrogenated Ti-DLC films [...] Read more.

The effect of irradiation by a hyperthermal-atomic-oxygen beam on hydrogenated titanium-doped diamond-like carbon (hydrogenated Ti-DLC) films, applied as a solid lubricant for equipment used in low-earth orbit was investigated. Unlike the film thickness of hydrogenated non-doped DLC films, that of hydrogenated Ti-DLC films was found to be constant after the films were exposed to atomic oxygen. In addition, bulk composition of the hydrogenated Ti-DLC film stayed constant, and in particular, hydrogen content in the film did not decrease. These results indicate that a hydrogenated Ti-DLC film can keep its low friction properties under vacuum. Surface chemical analysis showed that a titanium-oxide layer is form on the film by exposure to atomic oxygen. The thickness of the titanium oxide layer was estimated to be about 5 nm from the element distribution in the depth direction of the hydrogenated Ti-DLC films. The titanium-oxide layer was interpreted to protect the bulk film from erosion by hyperthermal atomic oxygen. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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872 KiB

Open AccessArticle

Characterization of Deformation Behavior of Individual Grains in Polycrystalline Cu-Al-Mn Superelastic Alloy Using White X-ray Microbeam Diffraction

by Eui Pyo Kwon, Shigeo Sato, Shun Fujieda, Kozo Shinoda, Ryosuke Kainuma, Kentaro Kajiwara, Masugu Sato and Shigeru Suzuki

Metals 2015, 5(4), 1845-1856; https://doi.org/10.3390/met5041845 - 9 Oct 2015

Cited by 4 | Viewed by 5250

Abstract

White X-ray microbeam diffraction was applied to investigate the microscopic deformation behavior of individual grains in a Cu-Al-Mn superelastic alloy. Strain/stresses were measured in situ at different positions in several grains having different orientations during a tensile test. The results indicated inhomogeneous stress [...] Read more.

White X-ray microbeam diffraction was applied to investigate the microscopic deformation behavior of individual grains in a Cu-Al-Mn superelastic alloy. Strain/stresses were measured in situ at different positions in several grains having different orientations during a tensile test. The results indicated inhomogeneous stress distribution, both at the granular and intragranular scale. Strain/stress evolution showed reversible phenomena during the superelastic behavior of the tensile sample, probably because of the reversible martensitic transformation. However, strain recovery of the sample was incomplete due to the residual martensite, which results in the formation of local compressive residual stresses at grain boundary regions. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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1101 KiB

Open AccessArticle

Twinning-Detwinning Behavior during Cyclic Deformation of Magnesium Alloy

by Soo Yeol Lee, Huamiao Wang and Michael A. Gharghouri

Metals 2015, 5(2), 881-890; https://doi.org/10.3390/met5020881 - 26 May 2015

Cited by 14 | Viewed by 5276

Abstract

In situ neutron diffraction has been used to examine the deformation mechanisms of a precipitation-hardened and extruded Mg-8.5wt.%Al alloy subjected to (i) compression followed by reverse tension (texture T1) and (ii) tension followed by reverse compression (texture T2). Two starting textures are used: [...] Read more.

In situ neutron diffraction has been used to examine the deformation mechanisms of a precipitation-hardened and extruded Mg-8.5wt.%Al alloy subjected to (i) compression followed by reverse tension (texture T1) and (ii) tension followed by reverse compression (texture T2). Two starting textures are used: (1) as-extruded texture, T1, in which the basal pole of most grains is normal to the extrusion axis and a small portion of grains are oriented with the basal pole parallel to the extrusion axis; (2) a reoriented texture, T2, in which the basal pole of most grains is parallel to the extrusion axis. For texture T1, the onset of extension twinning corresponds well with the macroscopic elastic-plastic transition during the initial compression stage. The non-linear macroscopic stress/strain behavior during unloading after compression is more significant than during unloading after tension. For texture T2, little detwinning occurs after the initial tension stage, but almost all of the twinned volumes are detwinned during loading in reverse compression. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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1362 KiB

Open AccessArticle

An in situ Study of NiTi Powder Sintering Using Neutron Diffraction

by Gang Chen, Klaus-Dieter Liss and Peng Cao

Metals 2015, 5(2), 530-546; https://doi.org/10.3390/met5020530 - 3 Apr 2015

Cited by 21 | Viewed by 8746

Abstract

This study investigates phase transformation and mechanical properties of porous NiTi alloys using two different powder compacts (i.e., Ni/Ti and Ni/TiH₂) by a conventional press-and-sinter means. The compacted powder mixtures were sintered in vacuum at a final temperature of [...] Read more.

This study investigates phase transformation and mechanical properties of porous NiTi alloys using two different powder compacts (i.e., Ni/Ti and Ni/TiH₂) by a conventional press-and-sinter means. The compacted powder mixtures were sintered in vacuum at a final temperature of 1373 K. The phase evolution was performed by in situ neutron diffraction upon sintering and cooling. The predominant phase identified in all the produced porous NiTi alloys after being sintered at 1373 K is B2 NiTi phase with the presence of other minor phases. It is found that dehydrogenation of TiH₂ significantly affects the sintering behavior and resultant microstructure. In comparison to the Ni/Ti compact, dehydrogenation occurring in the Ni/TiH₂ compact leads to less densification, yet higher chemical homogenization, after high temperature sintering but not in the case of low temperature sintering. Moreover, there is a direct evidence of the eutectoid decomposition of NiTi at ca. 847 and 823 K for Ni/Ti and Ni/TiH₂, respectively, during furnace cooling. The static and cyclic stress-strain behaviors of the porous NiTi alloys made from the Ni/Ti and Ni/TiH₂ compacts were also investigated. As compared with the Ni/Ti sintered samples, the samplessintered from the Ni/TiH₂ compact exhibited a much higher porosity, a higher close-to-total porosity, a larger pore size and lower tensile and compressive fracture strength. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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Review

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2092 KiB

Open AccessReview

Structural Dynamics of Materials under Shock Compression Investigated with Synchrotron Radiation

by Kouhei Ichiyanagi and Kazutaka G. Nakamura

Metals 2016, 6(1), 17; https://doi.org/10.3390/met6010017 - 15 Jan 2016

Cited by 20 | Viewed by 6764

Abstract

Characterizing material dynamics in non-equilibrium states is a current challenge in material and physical sciences. Combining laser and X-ray pulse sources enables the material dynamics in non-equilibrium conditions to be directly monitored. In this article, we review our nanosecond time-resolved X-ray diffraction studies [...] Read more.

Characterizing material dynamics in non-equilibrium states is a current challenge in material and physical sciences. Combining laser and X-ray pulse sources enables the material dynamics in non-equilibrium conditions to be directly monitored. In this article, we review our nanosecond time-resolved X-ray diffraction studies with 100-ps X-ray pulses from synchrotron radiation concerning the dynamics of structural phase transitions in non-equilibrium high-pressure conditions induced by laser shock compression. The time evolution of structural deformation of single crystals, polycrystals, and glass materials was investigated. In a single crystal of cadmium sulfide, the expected phase transition was not induced within 10 ns at a peak pressure of 3.92 GPa, and an over-compressed structure was formed. In a polycrystalline sample of Y₂O₃ stabilized tetragonal zirconia, reversible phase transitions between tetragonal and monoclinic phases occur within 20 ns under laser-induced compression and release processes at a peak pressure of 9.8 GPa. In polycrystalline bismuth, a sudden transition from Bi-I to Bi-V phase occurs within approximately 5 ns at 11 GPa, and sequential V–III–II–I phase transitions occur within 30 ns during the pressure release process. In fused silica shocked at 3.5 GPa, an intermediate-range structural change in the nonlinear elastic region was observed. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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Open AccessReview

In Situ Characterization Techniques Based on Synchrotron Radiation and Neutrons Applied for the Development of an Engineering Intermetallic Titanium Aluminide Alloy

by Petra Erdely, Thomas Schmoelzer, Emanuel Schwaighofer, Helmut Clemens, Peter Staron, Andreas Stark, Klaus-Dieter Liss and Svea Mayer

Metals 2016, 6(1), 10; https://doi.org/10.3390/met6010010 - 4 Jan 2016

Cited by 32 | Viewed by 10424

Abstract

Challenging issues concerning energy efficiency and environmental politics require novel approaches to materials design. A recent example with regard to structural materials is the emergence of lightweight intermetallic TiAl alloys. Their excellent high-temperature mechanical properties, low density and high stiffness constitute a profile [...] Read more.

Challenging issues concerning energy efficiency and environmental politics require novel approaches to materials design. A recent example with regard to structural materials is the emergence of lightweight intermetallic TiAl alloys. Their excellent high-temperature mechanical properties, low density and high stiffness constitute a profile perfectly suitable for their application as advanced aero-engine turbine blades or as turbocharger turbine wheels in next-generation automotive engines. As the properties of TiAl alloys during processing as well as during service are dependent on the phases occurring, detailed knowledge of their volume fractions and distribution within the microstructure is of paramount importance. Furthermore, the behavior of the individual phases during hot deformation and subsequent heat treatments is of interest to define reliable and cost-effective industrial production processes. In situ high-energy X-ray diffraction methods allow tracing the evolution of phase fractions over a large temperature range. Neutron diffraction unveils information on order-disorder transformations in TiAl alloys. Small-angle scattering experiments offer insights into the materials’ precipitation behavior. This review attempts to shine a light on selected in situ diffraction and scattering techniques and the ways in which they promoted the development of an advanced engineering TiAl alloy. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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Open AccessCorrection

Correction: Liss, K.-D., et al. Hydrostatic Compression Behavior and High-Pressure Stabilized β-Phase in γ-Based Titanium Aluminide Intermetallics. Metals 2016, 6, 165

by Klaus-Dieter Liss, Ken-Ichi Funakoshi, Rian Johannes Dippenaar, Yuji Higo, Ayumi Shiro, Mark Reid, Hiroshi Suzuki, Takahisa Shobu and Koichi Akita

Metals 2017, 7(9), 353; https://doi.org/10.3390/met7090353 - 7 Sep 2017

Viewed by 2846

Abstract

The authors would like to apologize for any inconvenience regarding misleading errors and inconsistencies in some of the units and one number, and wish to make the following corrections to this paper [1]:[...] Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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