scholarly journals Niobium Base Superalloys: Achievement of a Coherent Ordered Precipitate Structure in the Nb Solid-Solution

Crystals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 345
Author(s):  
François Saint-Antonin ◽  
Williams Lefebvre ◽  
Ivan Blum
Keyword(s):  
Solid Solution ◽  
Precipitation Hardening ◽  
Chemical Elements ◽  
Atom Probe ◽  
Lattice Parameter ◽  
Crystallographic Structure ◽  
New Family ◽  
Transmission Electron ◽  
Nickel Base ◽  
Precipitate Structure

In a previous work, the chemical elements necessary for the achievement of Niobium base superalloys were defined in order to get a structure equivalent to that of Nickel base superalloys, which contain ordered precipitates within a disordered solid-solution. It was especially emphasized that precipitation hardening in the Niobium matrix would be possible with the addition of Ni. The remaining question about the design of such Niobium superalloys concerned the achievement of ordered precipitates in crystalline coherence with the Nb matrix i.e., with a crystalline structure equivalent to the Nb crystal prototype and with a lattice parameter in coherency with that of the Nb matrix. In order to reduce the trial/error experimental work, a reasoning based on various data for the achievement of coherency is presented. Then, starting from the Nb-Hf-Ni ternary alloy thus defined, this paper demonstrates that the precipitation of an ordered Nb phase within a disordered Nb matrix can be achieved with lattice parameter coherency between the ordered precipitates and the disordered matrix. The chemistry and the crystallographic structure of the precipitates were characterized using Transmission Electron Microscopy and Atom Probe Tomography. These results can help to conceive a new family of Nb base superalloys.

Neutron diffraction of Cu–Zn–Sn ternary alloys: non-invasive assessment of the compositions of historical bronze/brass copper ternary alloys

2017 ◽  
Vol 50 (1) ◽  
pp. 49-60 ◽  
Author(s):  
Elisabetta Gliozzo ◽  
Winfried A. Kockelmann ◽  
Gilberto Artioli
Keyword(s):  
Solid Solution ◽  
Neutron Diffraction ◽  
Inductively Coupled Plasma ◽  
Lattice Parameter ◽  
Small Sample ◽  
Ternary Alloys ◽  
Crystallographic Structure ◽  
Present Sample ◽  
Non Invasive ◽  
Sample Set

Neutron diffraction can be used as a tool for the characterization of metal materials in a totally non-invasive mode. In binary alloys with two elements in solid solution, crystallographic structure analysis provides information on the overall element compositions of the metal, based on the linear relationship between elemental fractions and lattice parameters known as Vegard's rule. However, for ternary solid-solution alloys the derivation of the overall metal composition is not straightforward because the problem is mathematically underdetermined. A number of artificially produced samples in the ternary system Cu–Zn–Sn, widely used in antiquity for gunmetal, were investigated by time-of-flight neutron diffraction, inductively coupled plasma mass spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy and electron microprobe analysis. The multi-analysis approach allows definition of the limits and capabilities of neutron diffraction for obtaining the overall composition of a small sample set of ternary alloys, and thus moves the methodical approach a step forward even though it is applicable to the present sample set only. A relation showing an increasing Cu and Sn fraction counterbalanced by decreasing Zn content is presented, which allows the determination of the δ-phase composition from a lattice parameter measurement. Furthermore, the observed Zn loss up to 1.8 wt% for each melting step is of significance for the reconstruction of ancient technologies.

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.

Chemical and Structural Characterization of γ/γ′ Interfaces

2012 ◽  
Vol 463-464 ◽  
pp. 20-24
Author(s):  
Kai Zhao
Keyword(s):  
Atom Probe Tomography ◽  
Three Dimensional ◽  
Atom Probe ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Scale ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Nickel Base

More attention has been paid to the interfaces since mechanical properties of nickel-base superalloys are determined to some degree by them. The compositional transition across γ/γ′ interfaces and atomic structure of the interfaces was investigated using three-dimensional atom probe tomography and scanning transmission electron microscope equipped with high-resolution Energy Dispersive X-ray Spectrometry. Results show that no obvious segregation to the interfaces or ledges of the precipitates in the present experimental alloys has been observed. Also, adsorption of a solute to the interface was not observed. The interfaces are not flat as usually thought at an atomic scale. The interfacial thickness is about two atomic layers, i.e. 0.7 nm.

scholarly journals Влияние высоких давлений на формирование новых соединений в сплаве Al-=SUB=-86-=/SUB=-Ni-=SUB=-2-=/SUB=-Со-=SUB=-6-=/SUB=-Gd-=SUB=-6-=/SUB=--=SUP=--=SUP=-*-=/SUP=--=/SUP=-

2022 ◽  
Vol 64 (2) ◽  
pp. 149
Author(s):  
С.Г. Меньшикова ◽  
В.В. Бражкин
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Pressure ◽  
Phase Composition ◽  
Precipitation Hardening ◽  
Supersaturated Solid Solution ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Shrinkage Cavities

Abstract The structure, elemental and phase composition of the eutectic alloy Al86Ni2Со6Gd6 (hereinafter referred to as at.%) During the solidification of the melt from 1500oC at a rate of 1000oC/s under high pressure of 3 and 7 GPa have been investigated by X-ray diffraction analysis and electron microscopy. Solidification of the melt under high pressure leads to a change in the phase composition of the alloy and the formation of an anomalously supersaturated solid solution of α-Al (Gd). At a pressure of 7 GPa, new phases were synthesized: Al3Gd * (like Al3U) containing Co and Ni, with a primitive cube structure (cP4/2) with a lattice parameter a = 4.285 ± 0.002 Angstrem and Al8Co4Gd * (like Al8Cr4Gd) with a tetragonal structure (tI26/1) with parameters a = 8.906 ± 0.003 Angstrem and c = 5.150 ± 0.003 Angstrem. The structure of all the samples obtained is homogeneous, dense, finely dispersed, without shrinkage cavities and pores. The average microhardness of the samples is high due to solid solution and precipitation hardening.

scholarly journals Characterizing Precipitation Defects in Nickel Based 718 Alloy

2010 ◽  
Vol 636-637 ◽  
pp. 517-522 ◽  
Author(s):  
Aliou Niang ◽  
Julitte Huez ◽  
Jacques Lacaze ◽  
Bernard Viguier
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Stacking Fault ◽  
Crystallographic Structure ◽  
Chemical Ordering ◽  
Transmission Electron ◽  
Matrix Dislocation ◽  
Nickel Base

In the present study we examine the crystallographic structure of the , ’’ and  phases present in nickel base 718 alloy. The chemical ordering of Nb atoms and possible planar faults that may be observed in ’’ precipitates are detailed. High resolution transmission electron microscopy (HRTEM) observations of various faults are reported. The decomposition of a matrix dislocation to form a locked V shaped configuration is shown. The observation along [110] type direction allows to identify the type of defect, which is observed as a pure geometric stacking fault.

Atom Probe Analysis of the Compositions of γ′ AND γ″ Intermetallic Phases in Nickel-Based Superalloy 718

1990 ◽  
Vol 186 ◽  
Author(s):  
M. K. Miller ◽  
M. G. Burke
Keyword(s):  
Heat Treatment ◽  
Atom Probe ◽  
Nickel Base Superalloy ◽  
Probe Field ◽  
Nickel Based Superalloy ◽  
Transmission Electron ◽  
Transmission Electron Microscopy Characterization ◽  
Nickel Base ◽  
Microscopy Characterization ◽  
Base Superalloy

AbstractAn atom probe field ion microscopy and transmission electron microscopy characterization has been performed on the intragranular precipitates that are formed in a niobium-modified nickel-base superalloy 718 after the various stages of a multistage heat treatment. Atom probe results indicate that there is a wide variation in the compositions of the DO22-ordered γ″, the Ll2-ordered γ′ precipitates and the γ matrix with heat treatment and with position in the microstructure.

scholarly journals Synthesis of Pd-Fe System Alloy Nanoparticles by Pulsed Plasma in Liquid

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1068 ◽  
Author(s):  
Shota Tamura ◽  
Tsutomu Mashimo ◽  
Kenta Yamamoto ◽  
Zhazgul Kelgenbaeva ◽  
Weijan Ma ◽  
...  
Keyword(s):  
Solid Solution ◽  
Solution Structure ◽  
Lattice Parameter ◽  
Face Centered Cubic ◽  
Pulsed Plasma ◽  
X Ray ◽  
Transmission Electron ◽  
Vegard’S Law ◽  
Face Centered ◽  
Plasma In Liquid

We synthesized Pd-Fe series nanoparticles in solid solution using pulsed plasma in liquid with Pd-Fe bulk mixture electrodes. The Pd-Fe atomic percent ratios were 1:3, 1:1, and 3:1, and the particle size was measured to be less than 10 nm by high-resolution transmission electron microscopy (HR-TEM). The nanoparticles showed face-centered cubic structure. The lattice parameter increased with increasing Pd content and followed Vegard’s law, and energy-dispersive X-ray spectra were consistent with the ratios of the starting samples, which showed a solid solution state. The solid solution structure and local structure were confirmed by HR-TEM and X-ray absorption fine structure.

scholarly journals A Study of the Phase Decomposition of Fe-Ni-Al-Mo Alloys

1990 ◽  
Vol 186 ◽  
Author(s):  
M.K. Miller ◽  
M.G. Hetherington ◽  
J.R. Weertman ◽  
H.A. Calderon
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atom Probe ◽  
Lattice Parameter ◽  
Al Alloys ◽  
Phase Decomposition ◽  
Probe Field ◽  
Transmission Electron ◽  
The Matrix ◽  
Ion Microscopy

AbstractThe aging of β′ NiAl precipitates in ferritic Fe-Ni-Al alloys has been studied by transmission electron microscopy (TEM) and atom-probe field-ion microscopy (APFIM). The addition of Mo alters the lattice parameter of the phases and segregation of Mo to the interface between the matrix and the particles may alter the interfacial energy. The compositions of the matrix, precipitates and interfaces have been measured by TEM and APFIM. The results are compared.

Coherency loss in γ' precipitates in nickel-base superalloy

1983 ◽  
Vol 41 ◽  
pp. 244-245
Author(s):  
R. A. Ricks ◽  
Angus J. Porter
Keyword(s):  
Lattice Mismatch ◽  
Lattice Parameter ◽  
Nickel Base Superalloy ◽  
Large Size ◽  
The Matrix ◽  
Nimonic 80A ◽  
Interfacial Dislocations ◽  
Nickel Base ◽  
Coherency Loss ◽  
Nimonic 115

During a recent investigation concerning the growth of γ' precipitates in nickel-base superalloys it was observed that the sign of the lattice mismatch between the coherent particles and the matrix (γ) was important in determining the ease with which matrix dislocations could be incorporated into the interface to relieve coherency strains. Thus alloys with a negative misfit (ie. the γ' lattice parameter was smaller than the matrix) could lose coherency easily and γ/γ' interfaces would exhibit regularly spaced networks of dislocations, as shown in figure 1 for the case of Nimonic 115 (misfit = -0.15%). In contrast, γ' particles in alloys with a positive misfit could grow to a large size and not show any such dislocation arrangements in the interface, thus indicating that coherency had not been lost. Figure 2 depicts a large γ' precipitate in Nimonic 80A (misfit = +0.32%) showing few interfacial dislocations.

Fine Microstructure of a Mechanically Alloyed Oxide Dispersion Strengthened Nickel-Base Superalloy

1977 ◽  
Vol 35 ◽  
pp. 298-299
Author(s):  
Jordi Marti ◽  
Timothy E. Howson ◽  
David Kratz ◽  
John K. Tien
Keyword(s):  
Solid Solution ◽  
Volume Fraction ◽  
Stress Rupture ◽  
Oxide Dispersion Strengthened ◽  
Solid Solution Alloy ◽  
Oxide Dispersion ◽  
Creep And Stress Rupture ◽  
Mechanically Alloyed ◽  
Fine Microstructure ◽  
Nickel Base

The previous paper briefly described the fine microstructure of a mechanically alloyed oxide dispersion strengthened nickel-base solid solution. This note examines the fine microstructure of another mechanically alloyed system. This alloy differs from the one described previously in that it is more generously endowed with coherent precipitate γ forming elements A1 and Ti and it contains a higher volume fraction of the finely dispersed Y2O3 oxide. An interesting question to answer in the comparative study of the creep and stress rupture of these two ODS systems is the role of the precipitate γ' in the mechanisms of creep and stress rupture in alloys already containing oxide dispersoids.The nominal chemical composition of this alloy is Ni - 20%Cr - 2.5%Ti - 1.5% A1 - 1.3%Y203 by weight. The system receives a three stage heat treatment-- the first designed to produce a coarse grain structure similar to the solid solution alloy but with a smaller grain aspect ratio of about ten.

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