scispace - formally typeset
Search or ask a question

Showing papers on "Laves phase published in 2002"


Journal ArticleDOI
TL;DR: The phase diagram of the binary Fe-Zr system was redetermined by differential thermal analysis (DTA), electron-probe microanalysis (EPMA), x-ray diffraction (XRD), and metallography in the whole range of compositions as mentioned in this paper.
Abstract: The phase diagram of the binary Fe-Zr system was redetermined by differential thermal analysis (DTA), electron-probe microanalysis (EPMA), x-ray diffraction (XRD), and metallography in the whole range of compositions The stable intermetallic phases of the binary system are the cubic and the hexagonal polymorphs of the Fe2Zr Laves phase and the Zr-rich phases FeZr2 and FeZr3 While the cubic polymorph of the Laves phase is the stable structure at the stoichiometric Fe2Zr composition, the hexagonal C36-type polymorph of the Laves phase is a high-temperature phase that is found at Zr concentrations as low as 266 at% The Zr-rich phases FeZr2 and FeZr3 have small homogeneity ranges of about 05 at% FeZr2 is a high-temperature phase, stable between 780 and 951 °C FeZr3 decomposes peritectoidally at 851 °C The frequently reported phase Fe23Zr6 (Fe3Zr) is found not to be an equilibrium phase of the binary system

173 citations


Journal ArticleDOI
TL;DR: In this article, the structural and electrochemical properties of the superstoichiometric (Ti 0.8 Zr 0.2 ) x (x = 2, 3, 4, 5, 6) hydrogen storage alloys have been studied systematically.
Abstract: In this paper, the structural and electrochemical properties of the superstoichiometric (Ti 0.8 Zr 0.2 )(V 0.533 Mn 0.107 Cr 0.16 Ni 0.2 ) x (x = 2, 3, 4, 5, 6) hydrogen storage alloys have been studied systematically. It is found by X-ray diffraction and energy dispersive spectra analysis that all these alloys mainly consist of two phases, a C 14 Laves phase with hexagonal structure and a V-based solid solution phase with body-centered cubic structure. The lattice parameters and thus the cell volumes of the two phases all decrease when x is increased. The electrochemical measurements indicate that the maximum discharge capacity, the discharge equilibrium potential, the high rate dischargeability, the cyclic stability, the exchange current density I 0 , and the limiting current density I L of the alloys all increase with increasing x from 2 to 5. When x reaches 6, the discharge equilibrium potential, the high rate dischargeability, and the cyclic stability are still increasing proportionately, while the maximum discharge capacity, the exchange current density I 0 , and the limiting current density 1 L all decrease. Furthermore, the alloy electrodes are activated with more difficulty for the alloys with higher stoichiometry x. Consequently, we believe that the superstoichiometry is an effective way to improve the overall electrochemical properties of the Ti-based Laves-phase hydrogen storage alloys used for the negative electrodes of the Ni-MH secondary batteries.

62 citations


Journal ArticleDOI
TL;DR: In this paper, the authors designed new super heat-resistant 12 % Cr martensitic/ferritic steels using basic principles and concepts of physical metallurgy, to test and optimize model alloys and to investigate and clarify their behavior under long-term creep conditions with emphasis on microstructural stability and corrosion resistance.
Abstract: In the recent two decades advanced martensitic/ferritic 9-12 % Cr steels are recognized to be the most potential materials for 650°C Ultra Super Critical (USC) Power Plants. The critical issues are the improvement of long-term creep strength and corrosion resistance. The aim of the present research is to design new super heat-resistant 12 % Cr martensitic/ferritic steels using basic principles and concepts of physical metallurgy, to test and optimize model alloys and to investigate and clarify their behavior under long-term creep conditions with emphasis on microstructural stability and corrosion resistance. Fine distributions of stable precipitates, which block the movement of subgrain boundaries (M 23 C 6 carbides, Laves phase) and dislocations (MX carbonitrides) and delay coarsening of microstructure, are the key to high creep strength of this type of steels. Therefore, different carbide, nitride and Laves phase forming elements (Cr, W, Nb, V, Ta, Ti) have been used to provide precipitation hardening. Furthermore, the aim is to produce a sequence of precipitates with different kinetics, i.e. with precipitation of a new phase during coarsening of the prior one. Co has been used for obtaining 100% martensite initially and for slowing down diffusion processes and particle coarsening. The partial replacement of Co by Cu is also investigated to reduce costs. The first results of mechanical tests of the studied model alloys have shown positive effects of the addition of W and Ta as Laves phase and MX forming elements, respectively, as well as of the addition of B. Alloying with Co has also shown beneficial effects on the creep strength.

49 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe the rapid quenching effects on the solid-solution range of La(Ni, M)x (x=3-5) alloys prepared by melt spinning in discussing their hydrogen absorption properties.
Abstract: Many intermetallics such as AB5, AB2, A2B show the excellent hydrogen absorbing properties. Specially, LaNi5 compound has been extensively studied for the negative electrode of Ni–MH batteries. In today's use for the negative electrode of Ni–MH batteries, alloys must be single phase. But it is well known that it is difficult to make non-stoichiometric LaNi5 alloys as single phase because of its limited solid-solution range. The present study describes the rapid quenching effects on the solid-solution range of La(Ni, M)x (x=3–5) alloys prepared by melt spinning in discussing their hydrogen absorption properties. It is found that the single phase with CaCu5 crystal structure extends to LaNi4.65 compositional alloys. For fuel cell automobile, the alloys with high content of hydrogen must be developed. Strong candidates for this will be Vanadium based BCC alloys, which would be hard to be activated. Since it is well known that the Laves phases undergo easy activation treatment, it may be possible that the BCC phases will be easily activated if the alloys contain such Laves phases. The present study also found that Zr addition is effective on forming Laves phase as grain boundary phases in BCC phases in V–Ti–Zr–Ni alloys, and on improving the hydrogen absorbing properties. The study will be also extended to future hydrogen absorbing alloys with high capacity.

47 citations


Journal ArticleDOI
TL;DR: In this article, the determined defect structures are discussed, on the basis of the geometrical model, i.e. the atomic size factor, and a determined defect structure is introduced in Cr-rich and Zr-rich sides of stoichiometry.

45 citations


Journal ArticleDOI
TL;DR: In this article, microstructural observation and microchemical analysis of oxide dispersion-strengthened ferritic steels were carried out by neutrons up to 21 dpa and showed that the original high dislocation density did not change after neutron irradiation.

44 citations


Journal ArticleDOI
TL;DR: In this article, the effect of Nb on the high temperature proof strength of 0.46% Nb-added ferritic stainless steel was studied from the viewpoints of solid solution strengthening, precipitation strengthening, and precipitation strengthening during tensile test and/or preceding hold time.
Abstract: The effect of Nb on the high temperature proof strength of 0.46% Nb-added ferritic stainless steel was studied from the viewpoints of solid solution strengthening, precipitation strengthening, and precipitation strengthening during tensile test and/or preceding hold time. The results obtained were as follows. (1) The increase in high temperature proof strength in Nb-added ferritic stainless steel is particularly remarkable at around 700°C in comparison with that in Ti-added steels. (2) After aging treatment for 2 h at 700°C, in addition to the approximately 0.14% content of coarse Nb carbides and nitrides which had precipitated before this aging treatment, fine Fe 2 Nb Laves phase particles with a size of 0.02 μm precipitated out in an amount of approximately 0.3%, and virtually no solid solution Nb existed in the steel. The 700°C proof strength in this condition showed a value near the 700°C proof strength before the aging treatment, that is, when approximately 0.3 % solid solution Nb was present. (3) When aging treatment is performed at 700°C for 2 h or more, virtually all the added Nb precipitates out. The coarsening of the Fe 2 Nb laves phase particles within the range of 0.02-0.05 μm during aging at 700°C greatly decreases the high temperature proof strength at 700°C. (4) Cold rolled steel sheets of Nb-added ferritic stainless steel are normally manufactured by annealing at a temperature of 900°C or higher in order to cause recrystallization. Accordingly, before measurement of the proof strength at 700°C, the steel contains a large quantity of solid solution Nb. The phenomenon of particularly high strength at 700°C is considered to be attributable to the precipitation of this solid solution Nb as a fine Fe 2 Nb Laves phase during the tensile test and/or preceding hold time.

43 citations


Journal ArticleDOI
You-cai Zhu1, Hongming Pan1, Mingxia Gao1, Jie Ma1, S.Q. Li1, Qiuyan Wang1 
TL;DR: In this paper, the effect of Zr substitution for Ti on the microstructures and electrochemical properties of the electrode alloys has been studied, and it is found by X-ray powder diffraction and energy-dispersal spectroscope analyses that all the alloys consist of a C14 Laves main phase with hexagonal structure and a V-based solid solution secondary phase with b.c. structure.

42 citations


Journal ArticleDOI
TL;DR: In this article, a new class of heat resisting ferritic steels was investigated in the Fe-Cr-Nb and Fe−Cr-Ni systems, in which the major strengthener is the Fe2Nb Laves phase.
Abstract: A new class of heat resisting ferritic steels is investigated in the Fe–Cr–Nb and Fe–Cr–Nb–Ni systems, in which the major strengthener is the Fe2Nb Laves phase. Ferritic steels strengthened by Laves phase are expected to show excellent high temperature strength, while the brittleness of Laves phase may lower the toughness of the alloy. The α-Fe/Fe2Nb two-phase microstructure is selected to improve mechanical properties through changing volume fraction and morphology of Laves phase. Effects of Nb and Ni contents on the microstructure and mechanical properties of the alloys, fixed at 10 at.% Cr, have been systematically investigated. Mechanical properties were evaluated by tensile tests conducted at room temperature, 873 and 973 K. The tensile test revealed that the room temperature ductility decreases with increasing Nb content. The alloys with 1.0–1.5 at.% Nb are found to exhibit a good balance between room temperature ductility and high temperature strength.

42 citations


Journal ArticleDOI
TL;DR: In this paper, a creep model for metal-matrix composites has been extended to treat creep in Nb-based in-situ composites containing silicides in a creeping matrix.
Abstract: A creep model for metal-matrix composites has been extended to treat creep in Nb-based in-situ composites containing silicides in a creeping matrix. Model calculations revealed that the creep exponent of the in-situ composites is significantly influenced by the creep behavior of the stronger reinforcement (silicide or Laves) phase. The wide range of creep exponent (1–11) observed in Nb–Ti–Hf–Si in-situ composites can be explained on the basis of the rigid or creeping behavior of the silicide (or Laves) phase during creep in the in-situ composites. The application of the creep model to designing creep-resistant microstructure for Nb-based in-situ composites is discussed in conjunction with the roles of alloy addition and Peierls–Nabarro stress in influencing the creep resistance of the in-situ composites.

40 citations


Journal ArticleDOI
TL;DR: In this article, the intermediate phases in the Zr-Nb-Fe system have been investigated by X-ray diffraction, optical and electron microscopy and electron microprobe analysis.

Journal ArticleDOI
TL;DR: In this paper, the evolution and stability of particulate phases during creep of molybdenum- or tungsten-bearing 12Cr steels have been investigated in considerable depth, and data on Laves-phase precipitation kinetics as a function of time and temperature were quantified using the Wert-Zener equation in conjunction with the proprietary Thermo-Calc software.
Abstract: The evolution and stability of particulate phases during creep of molybdenum- or tungsten-bearing 12Cr steels have been investigated in considerable depth. The important finding is that the performance of Laves-phase precipitation in the molybdenum-bearing alloy is significantly different from that in the tungsten-bearing alloy. It is generally believed that such differences in kinetics will influence creep behavior. Data on Laves-phase precipitation kinetics as a function of time and temperature were quantified using the Wert-Zener equation in conjunction with the proprietary Thermo-Calc software, to determine equilibrium solute concentrations in these complex steels. The progressive depletion of Mo and W from the matrix as the particles of Laves phase evolve has been quantitatively modeled using experimental data obtained on both steels over a range of times and temperatures. The Isothermal coarsening rates of M23C6 and MX carbide particles were measured and found to occur at a constant volume fraction, in accordance with Ostwald ripening kinetics, with no significant differences in rates found between the two steels. The coarsening rates of M23C6 particles, found on subgrain boundaries, were consistent with a third-power dependence on particle radius, with an activation energy similar to that of volume diffusion. The smaller MX particles, which lay on subgrain-interior dislocation lines, were better explained by dislocation pipe diffusion, with a fifth-power dependence on particle radius and an activation energy approximately half that of volume diffusion.

Journal ArticleDOI
TL;DR: In this paper, a two-sublattice model with Mo and Zr on both sublattices was used to evaluate the Mo-Zr system using the calculation of phase diagrams (CALPHAD).
Abstract: The Mo-Zr system was critically assessed using the calculation of phase diagrams (CALPHAD) technique. The solution phases (liquid, bcc, and cph) were modeled with the Redlich-Kister expression for the excess Gibbs energy. The intermetallic Mo2Zr Laves phase, which has a measurable homogeneity range, was treated by a two-sublattice model with Mo and Zr on both sublattices. A set of self-consistent thermodynamic parameters for the Mo-Zr system was obtained. With the optimized functions for the Gibbs energy of the individual phases, most of the experimental information can be well reproduced.

Journal ArticleDOI
TL;DR: In this article, the authors reviewed the metallurgy of stainless steel-zirconium (SS-Zr) alloys with emphasis on Laves intermetallic behavior.
Abstract: Laves intermetallics (AB2 compounds) play an important role in the disposal of metallic waste resulting from the electrometallurgical treatment of spent nuclear fuel. These ZrFe2-type intermetallics incorporate and immobilize highly radioactive and long-lived constituents that are present in waste forms based on the stainless steel–zirconium (SS–Zr) alloys. This paper reviews the metallurgy of SS–Zr alloys with emphasis on Laves intermetallic behavior. Microscopy and diffraction studies have shown that all actinide elements and most fission product elements are present only in the ZrFe2-type intermetallics of a stainless steel–15 wt.% zirconium (SS–15Zr) waste form, whereas only molybdenum is incorporated in the ZrFe2-type intermetallics of a zirconium–8 wt.% stainless steel (Zr–8SS) alloy. Because of the importance of material durability to waste disposal, recent experiments have been aimed at determining the corrosion behavior of these intermetallics. Results from transmission electron microscopy of corrosion layers observed on the ZrFe2-type compounds are presented.

Journal ArticleDOI
TL;DR: The TiCr 2−x V x compounds with 0.0≤ x ≤ 1.2 series have been synthesised and characterised by X-ray powder diffraction as mentioned in this paper.

Journal ArticleDOI
TL;DR: In this article, the phase compositions of 50 alloys of Laves phase type were studied using X-ray, EDXA and electron microscopy methods and the interaction of alloys with hydrogen was studied by PC-isotherm method.

Journal ArticleDOI
TL;DR: In this article, the microstructure of the as-deposited Ti-Cr alloys primarily consists of a metastable bcc matrix of β-Ti(Cr) with precipitates along the grain boundaries.
Abstract: Ti-Cr alloys have been laser deposited from powder feedstock consisting of a blend of elemental powders using the laser-engineered net-shaping (LENS) process. The microstructure of the as-deposited Ti-Cr alloys primarily consists of a metastable bcc matrix of β-Ti(Cr) with precipitates along the grain boundaries. The grain-boundary precipitates have been identified to be of three types, essentially pure hcp Ti, an alloyed hcp phase designated α-Ti(Cr), and the C14 TiCr2 Laves phase. Initial stages of decomposition, visible within the β matrix, suggest a spinodal clustering process resulting in a fine dispersion of second phases. Diffraction studies have revealed the presence of fine precipitates of α within the β matrix. The evidence for the precipitation of the metastable ω phase within the β matrix is not strong. The phase evolution in the LENS-deposited Ti-Cr alloy has been discussed in the context of rapid solidification and the enthalpy of mixing of the elemental powders.

Journal ArticleDOI
TL;DR: In this paper, the icosahedral (i) phase was observed to form from liquid in as-cast Ti 33 Zr 46 Ni 21 and Ti 37 Zr 42 Ni 21 alloys.
Abstract: Previously, the formation of the thermodynamically stable icosahedral Ti-Zr- Ni i-(Ti-Zr-Ni) phase has been observed in rapidly quenched alloys, or by a low-temperature solid-state transformation from crystal phases that form at higher temperatures. Here we report the nucleation and growth of the icosahedral (i) phase directly from the liquid in as-cast Ti 33 Zr 46 Ni 21 and Ti 37 Zr 42 Ni 21 alloys. Diffraction patterns obtained by transmission electron microscopy and X-ray diffraction confirm the phase identity. Differential scanning calorimetry measurements show an endothermic transformation from the i-phase to a phase mixture of a C14 Laves phase and a solid-solution phase, demonstrating that this i-phase is also stable. The short time that the liquid remains in the Laves-phase-forming field and the higher nucleation rate for the i-phase, owing to strong similarities in the local structures of the i-phase and liquid, allow i-phase nucleation and growth directly from the liquid.

Journal ArticleDOI
TL;DR: In this article, the lattice constant and magnetic properties of compounds Nd1-xTbxCo2 were investigated by x-ray power diffraction and magnetic measurements, and it was shown that these compounds exhibit a field-induced metamagnetic transition from a weak ferrimagnetism to a strong ferrimagnetic transition in the vicinity of x(c).
Abstract: The lattice constant and magnetic properties of compounds Nd1-xTbxCo2 were investigated by x-ray power diffraction and magnetic measurements. The lattice constant and Curie temperature show linear variations with the Tb concentration, while the saturation moment exhibits an anomaly at a critical concentration x(c)approximate to0.33. The compounds exhibit a field-induced metamagnetic transition from a weak ferrimagnetism to a strong ferrimagnetism in the vicinity of x(c). (C) 2002 American Institute of Physics.

Journal ArticleDOI
TL;DR: In this article, a thermal-aged 9Cr-2W-V, Ta steel (JLF-1) and JLS-series were used for D-T fusion reactors and microstructural features were observed using transmission electron microscope with energy dispersive X-ray spectrometer.

Journal ArticleDOI
TL;DR: In this article, the authors measured the hydrogen diffusivity in C15-Hf Ti2Hx (3.9, 3.9 and 4.2) by means of the pulsed-field-gradient nuclear magnetic resonance (PFG-NMR) between 220 and 500 K.
Abstract: Measurements of the hydrogen diffusivity in the hydrogen-stabilized Laves phase compound C15-Hf Ti2Hx (3.9≤x≤4.2) have been performed by means of the pulsed-field-gradient nuclear magnetic resonance (PFG-NMR) between 220 and 500 K. The activation enthalpies for hydrogen diffusion obtained by fitting an Arrhenius expression to the diffusivities measured at a given concentration x are Ha = 240 meV (x = 3.9), 210 meV (x = 4.0) and 235 meV (x = 4.2). The proton spin-lattice relaxation rates Γ1 have been measured on the same samples over wide temperature ranges and at different resonance frequencies. Above about 250 K, the Γ1 data are well represented by a relaxation model for jumps between tetrahedral [Hf Ti3] sites. A comparison with the PFG results shows that these jumps correspond to long-range diffusion. At lower temperatures, the Γ1 data indicate localized motion of hydrogen, presumably within hexagons formed by six tetrahedral [Hf2Ti2] sites, which has no effect on the PFG measurements. Similar diffusion mechanisms have been observed previously in C15-ZrTi2Hx (x≈4).

Journal ArticleDOI
Yan-hui Xu, Changpin Chen1, Xiaolin Wang, Yongquan Lei1, Qidong Wang1 
TL;DR: In this article, a Ti-based AB2 Laves phase hydrogen storage electrode alloys are prepared and their electrochemical cycle stability is studied, including Ti0.7Zr0.5V0.2Cr0.4Ni0.8V 0.8−xAlx (x=0.6), 0.4, 0.1, 1.4 and 1.7) and Ti1.0Zr 0.2Mn1.

Journal ArticleDOI
TL;DR: In this article, a characterisation of modified F-82H steel was carried out, where microstructural studies together with mechanical testing were conducted on the steel in the as received state and after thermal aging in the temperature range 300-600°C for periods up to 5000 h.
Abstract: Metallurgical characterisation of modified F–82H steel was carried out. Microstructural studies together with mechanical testing were conducted on the steel in the as received state and after thermal aging in the temperature range 300–600°C for periods up to 5000 h. In addition, precipitate development during creep tests at 600 and 650°C was studied. During thermal aging, the general microstructure of the steel (tempered martensite with M23C6 precipitates) remained stable up to 500°C. However, at 550 and 600°C, in addition to the M23C6 carbides, Laves phase and precipitates with intermediate composition between carbides and Laves phase were observed. In terms of mechanical properties, the F–82H modified steel exhibited the same values of hardness, ultimate tensile stress and 0.2% proof stress, and similar creep rupture strength, regardless of the material condition studied. In contrast, aging treatments at 550 and 600°C caused a significant decrease in impact properties, essentially attributable t...

Journal ArticleDOI
Yunfeng Zhu1, Hongge Pan1, Mingxia Gao1, Yongfeng Liu1, Qidong Wang1 
TL;DR: In this paper, the multi-component, multiphase Ti-based hydrogen storage alloys (Ti 0.8 Zr 0.2 )(V 0.533 Mn 0.107 Cr 0.16 Ni 0.5, 7) have been studied systematically in order to find the lattice parameters and unit cell volumes of the C14 Laves phase and the V-based solid solution all decrease when x is increased.

Journal ArticleDOI
Yunfeng Zhu1, Hongge Pan1, Mingxia Gao1, Yongfeng Liu1, Qidong Wang1 
TL;DR: In this article, the effects of annealing treatment on the alloy structures of the hydrogen storage electrode alloy (Ti0.8Zr0.2)(V0.533Mn0.107Cr0.16Ni0.4) have been investigated.

Journal ArticleDOI
TL;DR: In this article, a time-composition-temperature diagram of Fe-10mass%Cr-W-C quaternary steels is calculated on the basis of the system free energy theory proposed by Koyama and Miyazaki.
Abstract: In order to elucidate the microstructure evolution in advanced high Cr heat resisting ferritic steels, a time-composition-temperature diagram of Fe-10mass%Cr-W-C quaternary steels is calculated on the basis of the system free energy theory proposed by Koyama and Miyazaki. Microstructures of the steels are predictable using such a system free energy consisting of chemical free energy, interface energy and strain energy between the matrix and precipitates in the steels. In this study, our attention is focused on the Laves phase as the precipitate, because this phase is formed in recently developed heat resisting ferritic steels and affects their creep strength largely. The calculations conducted in the Fe-Cr-W-C quaternary steels lead to the following findings: (i) The Laves phase is not formed in those steels containing less than 0.4 mol% W (about 1.4 mass% W) even after a long term aging at 923K; (ii) Only granular Laves phase precipitates in the steel containing 0.4 mol% W to 1.05 mol% W (about 3.5 mass% W) even in the early stage of aging at 923 K; (iii) The morphological change of the Laves phase from the fine coherent precipitate to the granular one occurs in a regular aging sequence in the steel if it contains more than 1.05 mol% W; (iv) Coherent precipitation line for the Laves phase is determined in the quasi-binary phase diagram as a function of the W content. These findings obtained theoretically are consistent with experimental results.

Journal ArticleDOI
Jeong-Gun Park1, Hwan-Young Jang1, Sang-Cheol Han1, Paul S. Lee1, Jai-Young Lee1 
TL;DR: In this article, several TiMn 2 -based C14 Laves phase alloys were prepared and their hydrogen storage properties were studied in order to develop a suitable material for metal hydride heat pump applications.
Abstract: Several TiMn 2 -based C14 Laves phase alloys were prepared and their hydrogen storage properties were studied in order to develop a suitable material for metal hydride heat pump applications. The metal hydride should have a suitable plateau pressure under 10 atm and low sloping. The plateau pressure was effectively decreased by the partial substitutions of Zr for Ti, while the slope was increased. It was found that the decrease of stoichiometry and the substitution of V, Cu were very effective in improving the sloping properties and the improvement of sloping properties was mainly attributed to the strain energy effect. After careful balancing of the substitution effects of the alloying elements, it was found that (Ti 0.8 Zr 0.2 ) 1.05 Mn 0.8 Cr 1.05 V 0.05 Cu 0.1 alloy showed good plateau characteristics with considerably small hysteresis and sloping.

Journal ArticleDOI
TL;DR: In this article, the twinning behavior of the C15 HfV2+Nb Laves phase was investigated at very low temperature down to 4.2 K and conventional transmission electron microscopy were conducted to investigate the twining behavior of two phase C15/bcc two-phase alloy with C15 matrix.
Abstract: Compression tests at very low temperature down to 4.2 K and conventional transmission electron microscopy were conducted to investigate the twinning behavior of the C15 HfV2+Nb Laves phase. We chose two phase C15/bcc alloys to improve the ambient temperature ductility since the single Laves phase intermetallic compound is brittle. Transmission electron microscopy revealed that substantial mechanical twinning takes place in the C15 Laves phase matrix at room temperature and 77 K. A deep minimum in the flow stress, with a drop of nearly 500 MPa, appears at around 77 K in the C15/bcc two-phase alloy with C15 matrix. Since no such anomaly is seen in the bcc phase, we believe that the cause of this can be attributed to mechanical twinning in the C15 Laves phase. Twin bands observed in the C15 matrix of deformed samples at both 298 and 77 K can be classified into three categories by their thickness; coarse twin bands about 10 nm to several hundred nm thick, fine twin bands around 3–10 nm thick, and ultra fine twin bands with average thickness of 1.5 nm. A high density of ultra-fine twin bands is the characteristic feature of twinning in the C15 matrix. They belong to the 〈112〉(111) twinning system and commonly intersect with each other.

Journal ArticleDOI
TL;DR: Zircaloy-4 foils were analysed by in situ neutron diffraction experiments when submitted to a water corrosion process simulating PWR conditions (high temperature and high steam pressure) as discussed by the authors.

Journal ArticleDOI
TL;DR: In this article, the effects of substitution of V for Mn atoms on phase structure and hydrogen storage properties are studied and the main phases were found to be C14 and C15 Laves phase.