scholarly journals Precipitation Process in a Cu-Ni-Be Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 432-436 ◽  
Author(s):  
Chihiro Watanabe ◽  
Ryoichi Monzen
Keyword(s):  
Electron Microscopy ◽  
Precipitation Process ◽  
Average Thickness ◽  
Precipitation Sequence ◽  
Transmission Electron ◽  
The Matrix ◽  
Precipitated Phases ◽  
Kinetics Of ◽  
Ledge Mechanism ◽  
Habit Planes

The precipitation process in an aged Cu-1.9wt%Ni-0.3wt%Be alloy has been examined by high-resolution transmission electron microscopy. The precipitation sequence found is: Guinier- Preston (G.P.) zones → γ'' → γ' → stable γ. The disk-shaped G.P. zones and the disk-shaped γ'', γ' and γ precipitated phases are composed of monolayers of Be atoms on {100}αof the Cu matrix and alternative Be and Ni matrix layers parallel to {100}α. The γ'' phases consisting of two to eight Be-layers has a body-centered tetragonal (bct) lattice witha=b=0.24 nm andc=0.28 nm. The γ' or γ phase is bct witha=b=0.24 nm andc=0.26 nm ora=b=0.26 nm andc=0.27 nm. The γ'', γ' or γ phase aligns with the matrix according to the Bain orientation relationship. The growth kinetics of disk-shaped γ precipitates on aging at 500°C has been also investigated. The {001}αhabit planes of the γ precipitates migrate by a ledge mechanism. The average thickness of the γ disks increases with aging timetast1/2. An analysis of experimental data using a kinetic model yields the diffusivity of solute in the Cu matrix, which is in agreement with the reported diffusivity of Ni in Cu.

Microstructure and Properties of Cu-Cr-Zr-Ag Alloy

2018 ◽  
Vol 941 ◽  
pp. 1613-1617 ◽  
Author(s):  
Li Jun Peng ◽  
Xu Jun Mi ◽  
Hao Feng Xie ◽  
Yang Yu ◽  
Guo Jie Huang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
Phase Transformation ◽  
High Resolution ◽  
Aging Process ◽  
Precipitation Sequence ◽  
Transmission Microscopy ◽  
Transmission Electron ◽  
The Matrix

The Cr precipitation sequence in Cu-Cr-Zr-Ag alloy during the aging process at 450°C could be obtained by Transmission electron microscopy (TEM) and High-resolution transmission microscopy (HRTEM) in the study. The strengthening curve shows a unimodal type and the tensile strength trends to peak when the aged for 4h. The Cr phase transformation of Cu-Cr-Zr-Ag aged at 450°C is supersaturated solid sloution→G.P zones→fcc Cr phase→order fcc Cr phase→bcc Cr phase. The orientation relationship between bcc Cr precipitates and the matrix change from cube-on-cube to NW-OR.

Precipitation Phenomena in Implanted Ionic Oxide MgO

1981 ◽  
Vol 7 ◽  
Author(s):  
A. Perez ◽  
M. Treilleux ◽  
P. Thevenard ◽  
G. Abouchacra ◽  
G. Marest ◽  
...  
Keyword(s):  
Rutherford Backscattering Spectrometry ◽  
Spinel Ferrite ◽  
Precipitation Process ◽  
X Ray Diffraction ◽  
Cationic Sublattice ◽  
Alkali Ions ◽  
Transmission Electron ◽  
The Matrix ◽  
Precipitation Phenomena ◽  
Precipitated Phases

ABSTRACTMgO single crystals implanted with alkali ions (Li+, Na+, K+ and Rb+),Fe+, In+ and Au+ ions have been studied after implantation with doses up to 1017 ions.cm−2 and after annealing at temperatures up to 1100°C.In order to characterize defects and precipitated phases, several techniques have been associated depending on the implanted ions : optical absorption, transmission electron microscopy, Rutherford backscattering spectrometry, conversion electron Mössbauer spectroscopy and X-ray diffraction at oblique incidence. Directly after implantation the intrinsic defects in the anionic sublattice (F, F+, F2-centers) and in the cationic sublattice (V−-centers) are observed. As to the implanted species, two precipitation processes are observed : (i) the implanted ions precipitate independently of the matrix elements. This is the case of alkali ions which form alkali metal precipitates. (ii) the implanted species precipitate with those of the matrix to form compounds. This is observed with iron which forms oxide precipitates and spinel ferrite. In the case of indium and gold, the precipitation process occurs with the cations of the matrix to form binary alloys : Mg3In and Au3Mg.

scholarly journals PHASE-TRANSFORMATION DYNAMICS AND CHARACTERIZATION OF PRECIPITATES IN THE Cu-3Ti-3Ni-0.5Si ALLOY

2021 ◽  
Vol 55 (4) ◽  
Author(s):  
Jia Liu ◽  
Jituo Liu ◽  
Xianhui Wang ◽  
Chong Fu ◽  
Yanlong Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electrical Conductivity ◽  
Phase Transformation ◽  
Volume Fraction ◽  
Formation Enthalpy ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
The Matrix ◽  
Diffraction Patterns ◽  
Precipitated Phases

In this paper we investigated the phase-transformation dynamics of the Cu-3Ti-3Ni-0.5Si alloy by applying the Avrami method to phase-transformation dynamics and electrical conductivity based on the relationship between the electrical conductivity and the volume fraction of precipitates in the Cu-3Ti-3Ni-0.5Si alloy. The results corroborated well with the experimental data. The microstructure and precipitated phases were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The analysis of the selected-area electron-diffraction patterns indicated that the precipitates formed in the matrix of the Cu-3Ti-3Ni-0.5Si alloy during aging, correspond to the Ni3Ti, Ni3Si, and Ni2Si phases. According to the values of formation enthalpy and cohesive energy determined by first-principle calculations, the formation of the Ni2Si phase is more favorable compared to the Ni3Si and Ni3Ti phases, and the Ni3Ti exhibits improved structural stability compared to the Ni2Si and Ni3Si phases.

scholarly journals Multiple Influences of Molybdenum on the Precipitation Process in a Martensitic PH Stainless Steel

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1118
Author(s):  
Mattias Thuvander ◽  
Marcus Andersson ◽  
Krystyna Stiller
Keyword(s):  
Electron Microscopy ◽  
Stainless Steel ◽  
Atom Probe Tomography ◽  
Precipitation Hardening ◽  
Atom Probe ◽  
Precipitation Process ◽  
Transmission Electron ◽  
Initial Stage ◽  
The Matrix ◽  
Mo Content

Molybdenum has been found to influence the complex precipitation process in a martensitic precipitation hardening stainless steel during aging at 475 °C in several different ways. Three steels with different Mo content (0, 1.2 and 2.3 at.%) were investigated. Studies of the microstructure were performed with atom probe tomography and energy filtered transmission electron microscopy. It is shown that, at the initial stage of aging, a faster nucleation of Cu-rich clusters takes place with increasing Mo content. The Cu-clusters act as precipitation sites for other solute elements and promote the nucleation of Ni-rich phases. During further aging, a higher Mo content in the material instead slows down the growth and coarsening of the Ni-rich phases, because Mo segregates to the interface between precipitate and matrix. Additionally, Mo promotes decomposition of the matrix into α and α′ regions. After longer aging times (>40 h) quasicrystalline Mo-rich R′ phase forms (to a greater extent in the material having the highest Mo content). The observations serve to understand the hardness evolution during aging.

scholarly journals Oxygen Induced Phase Transformation in TC21 Alloy with a Lamellar Microstructure

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 163
Author(s):  
Shu Wang ◽  
Yilong Liang ◽  
Hao Sun ◽  
Xin Feng ◽  
Chaowen Huang
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
Oxygen Uptake ◽  
Titanium Alloys ◽  
Electron Backscatter Diffraction ◽  
Lamellar Microstructure ◽  
Α Phase ◽  
Transmission Electron ◽  
The Matrix ◽  
Oxygen Ingress

The main objective of the present study was to understand the oxygen ingress in titanium alloys at high temperatures. Investigations reveal that the oxygen diffusion layer (ODL) caused by oxygen ingress significantly affects the mechanical properties of titanium alloys. In the present study, the high-temperature oxygen ingress behavior of TC21 alloy with a lamellar microstructure was investigated. Microstructural characterizations were analyzed through optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Obtained results demonstrate that oxygen-induced phase transformation not only enhances the precipitation of secondary α-phase (αs) and forms more primary α phase (αp), but also promotes the recrystallization of the ODL. It was found that as the temperature of oxygen uptake increases, the thickness of the ODL initially increases and then decreases. The maximum depth of the ODL was obtained for the oxygen uptake temperature of 960 °C. In addition, a gradient microstructure (αp + β + βtrans)/(αp + βtrans)/(αp + β) was observed in the experiment. Meanwhile, it was also found that the hardness and dislocation density in the ODL is higher than that that of the matrix.

The effect of composition and cooling rate on the structure of rapidly solidified (Fe, Ni)3Al–C alloys

1989 ◽  
Vol 4 (1) ◽  
pp. 44-49 ◽  
Author(s):  
S. A. Myers ◽  
C. C. Koch
Keyword(s):  
Cooling Rate ◽  
Base Alloy ◽  
Weight Percent ◽  
Quench Rate ◽  
Transmission Electron ◽  
Metastable Structures ◽  
Metastable Structure ◽  
The Matrix ◽  
Rapidly Solidified ◽  
Kinetics Of

There is controversy in the literature regarding the existence of the metastable γ′ phase with an ordered Ll2 structure in rapidly solidified Fe–Ni–Al–C alloys. In this study, the quench rate–metastable structure dependence was examined in the Fe–20Ni–8Al–2C (weight percent) alloy. The effect of silicon on the kinetics of phase formation was studied by adding two weight percent silicon to a base alloy of Fe–20Ni–8Al–2C. Samples were rapidly solidified in an arc hammer apparatus and examined by transmission electron microscopy. In the Fe–20Ni–8Al–2C alloy, the nonequilibrium γ′ and γ phases were found in foils 65 to 100 μm thick. At higher quench rates, i.e., thinner samples, the matrix was observed to be disordered fcc γ with K-carbide precipitates. Samples containing silicon were found to have a matrix composed of γ′ and γ structures when the foils were thicker than 40 μm. At higher quench rates, the matrix was disordered fcc γ with K-carbide precipitates. The nonequilibrium γ′ and γ structures are present in samples with or without silicon, but are observed at higher cooling rates with the addition of silicon. This sensitivity to cooling rate and composition in resulting metastable structures may explain the differences reported in the literature for these rapidly solidified materials.

Atomic-scale structural and compositional analyses of Ruddlesden-Popper planar faults in AO-excess SrTiO3 (A = Sr2+, Ca2+, Ba2+) ceramics

2009 ◽  
Vol 24 (8) ◽  
pp. 2596-2604 ◽  
Author(s):  
Sašo Šturm ◽  
Makoto Shiojiri ◽  
Miran Čeh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dark Field ◽  
Atomic Scale ◽  
Transmission Electron ◽  
Initial Stage ◽  
Final Microstructure ◽  
Scanning Transmission ◽  
The Matrix ◽  
Annular Dark Field

The microstructure in AO-excess SrTiO3 (A = Sr2+, Ca2+, Ba2+) ceramics is strongly affected by the formation of Ruddlesden-Popper fault–rich (RP fault) lamellae, which are coherently intergrown with the matrix of the perovskite grains. We studied the structure and chemistry of RP faults by applying quantitative high-resolution transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy analyses. We showed that the Sr2+ and Ca2+ dopant ions form RP faults during the initial stage of sintering. The final microstructure showed preferentially grown RP fault lamellae embedded in the central part of the anisotropic perovskite grains. In contrast, the dopant Ba2+ ions preferably substituted for Sr2+ in the SrTiO3 matrix by forming a BaxSr1−xTiO3 solid solution. The surplus of Sr2+ ions was compensated structurally in the later stages of sintering by the formation of SrO-rich RP faults. The resulting microstructure showed RP fault lamellae located at the surface of equiaxed BaxSr1-xTiO3 perovskite grains.

Observation of the nucleation kinetics of Si quantum dots on SiO2 by energy filtered transmission electron microscopy

2003 ◽  
Vol 205 (1-4) ◽  
pp. 304-308 ◽  
Author(s):  
G. Nicotra ◽  
S. Lombardo ◽  
C. Spinella ◽  
G. Ammendola ◽  
C. Gerardi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Nucleation Kinetics ◽  
Transmission Electron ◽  
Kinetics Of ◽  
Si Quantum Dots

The orientation relationships of nanobelt-like Si2Hf precipitates in an Al–Si–Mg–Hf alloy

2016 ◽  
Vol 49 (4) ◽  
pp. 1223-1230 ◽  
Author(s):  
Xueli Wang ◽  
Huilan Huang ◽  
Xinfu Gu ◽  
Yanjun Li ◽  
Zhihong Jia ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Coincident Site Lattice ◽  
Orthorhombic Structure ◽  
Orientation Relationships ◽  
Lattice Distribution ◽  
Site Lattice ◽  
Transmission Electron ◽  
Habit Planes ◽  
Al Matrix

The orientation relationships (ORs) between the Al matrix and Si2Hf precipitates with an orthorhombic structure in an Al–Si–Mg–Hf alloy after heat treatment at 833 K for 20 h were investigated by transmission electron microscopy and electron diffraction. Four ORs are identified as (100)Al||(010)p, (0\overline {1}1)Al||(101)pand [011]Al||[\overline {1}01]p; (11\overline {1})Al||(010)pand [011]Al||[\overline {1}01]p; (12\overline {1})Al||(010)p, (101)Al||(100)pand [1\overline {11}]Al||[001]p; (\overline {11}1)Al||(010)pand [112]Al||[\overline {1}01]p. The habit planes of these four ORs are rationalized by the fraction of good atomic matching sites at the interface. In addition, the formation of Si2Hf precipitates with a nanobelt-like morphology is interpreted on the basis of the near-coincident site lattice distribution.

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