Interface Structure of Some Precipitates in Austenitic Stainless Steels

1981 ◽  
Vol 39 ◽  
pp. 292-293
Author(s):  
J. Bentley
Keyword(s):  
Dominant Role ◽  
Austenitic Stainless Steels ◽  
Lattice Parameter ◽  
Interfacial Structure ◽  
Detailed Knowledge ◽  
Face Centered Cubic ◽  
Orientation Relationships ◽  
The Matrix ◽  
High Resolution Tem ◽  
Fcc Phase

Interphase boundaries often play a dominant role in high-temperature materials properties such as deformation and fracture or radiation damage. A detailed knowledge of the interfacial structure is required to understand the relationship between microstructure and properties. High-resolution TEM observations have been made of the interfacial structure of two carbides (M23C6 and MC) and an intermetallic compound (sigma) in 300 series austenitic stainless steels.Precipitates with well-defined orientation relationships and interface planes were chosen in order that the determined structures would be generally applicable in a range of property-structure correlations.Chromium-rich M23C6 (τ) is a face-centered cubic (fcc) phase with a lattice parameter (ao)τ ∼ 1.06 nm ≈ 2.97(ao)γ which forms with a cube-on-cube orientation relationship with the matrix (γ) and with {111} and {110} interfaces. In order to accommodate the “mismatch” of ∼1% between the matrix and precipitate, interface dislocations with separations of 10—20 nm are expected and have been observed previously.

High-resolution TEM of precipitate plate growth by diffusional and displacive transformation mechanisms

1988 ◽  
Vol 46 ◽  
pp. 760-761
Author(s):  
J. M. Howe ◽  
G. J. Mahon
Keyword(s):  
High Resolution ◽  
Interfacial Structure ◽  
Cu Alloy ◽  
Transmission Electron ◽  
The Matrix ◽  
High Resolution Tem ◽  
Transformation Mechanisms ◽  
Interfacial Motion ◽  
Compositional Changes ◽  
Diffusional Transformation

Precipitate plates can grow by diffusional, displacive or coupled diffusional/displacive (for interstitial alloys) mechanisms of interfacial motion. In each case, it is necessary to characterize the atomic details of the structural and/or compositional changes which occur at the matrix/precipitate interface in order to fully understand the transformation mechanisms. High-resolution transmission electron microscopy (HRTEM) provides unique capabilities for obtaining such information. This is illustrated below by HRTEM studies of interfacial structure performed on precipitate plates which grow by diffusional and diffusionless mechanisms in Al-Li-Cu and Fe-Cr-C alloys, respectively.The growth of hexagonal T2 (Al2CuLi) precipitate plates on the {111{α f.c.c. matrix planes in an Al-2wt.%Li-1wt.%Cu alloy is an example of a diffusional transformation which requires substantial changes in both crystal structure and composition at the transformation interface. The growth of b.c.t. α martensite plates on the {252{γ f.c.c. austenite planes in a Fe-8wt.%Cr-1wt.%C alloy is more complicated than the T1 transformation crystallographically, but it is a good example of a diffusionless transformation which requires only a change in structure at the transformation interface.

Effect of aging in hydrogen atmosphere on electrical conductivity of Cu–3at.%Ti alloy

2008 ◽  
Vol 23 (2) ◽  
pp. 473-477 ◽  
Author(s):  
Satoshi Semboshi ◽  
Toyohiko J. Konno
Keyword(s):  
Electrical Conductivity ◽  
Aging Time ◽  
Lattice Parameter ◽  
Hydrogen Atmosphere ◽  
Face Centered Cubic ◽  
Electrical Conductivities ◽  
The Face ◽  
Face Centered ◽  
Fcc Phase ◽  
Pure Cu

The electrical conductivities of Cu–3at.%Ti alloys aged at 773 K in a hydrogen atmosphere were investigated as a function of aging time. The electrical conductivity of the quenched alloy, 5.2% International Annealed Copper Standard (IACS), improved with aging time to 66% IACS after 48 h. This was mainly caused by the dilution of the Cu–Ti solid solution in the alloy, which is supported by the fact that the lattice parameter of the face-centered cubic (fcc) phase approaches that of pure Cu by aging in a hydrogen atmosphere.

scholarly journals Characterization of crystal structure and precipitation crystallography of a new MgxAl2−xGd phase in an Mg97Al1Gd2alloy

2016 ◽  
Vol 49 (4) ◽  
pp. 1177-1181 ◽  
Author(s):  
X.-F. Gu ◽  
T. Furuhara
Keyword(s):  
Crystal Structure ◽  
Lattice Parameter ◽  
Face Centered Cubic ◽  
Laves Phases ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Matrix ◽  
The Face ◽  
Face Centered

The composition, crystal structure and precipitation crystallography of a newly found precipitate are characterized by Cs-corrected scanning transmission electron microscopy. The composition of the plate-like precipitate could be expressed as MgxAl2−xGd (x= 0.38), and its crystal structure is the same as the face-centered cubic type Laves phases Mg2Gd and Al2Gd, with a lattice parameter of 7.92 Å (space group No. 227, Fd\overline 3m). The orientation relationship between the matrix and precipitate is found to be (0001)m//(111)pand [10\overline 10]m//[1\overline 10]p, and the habit plane is parallel to the (0001)m//(111)pplane. In addition, this preferred crystallography of phase transformation is well explained on the basis of the atomic matching at the interface.

scholarly journals Elastic Parameters of Paramagnetic Fe–20Cr–20Ni-Based Alloys: A First-Principles Study

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 792 ◽  
Author(s):  
Noura Al-Zoubi
Keyword(s):  
First Principles ◽  
Theoretical Data ◽  
Austenitic Stainless Steels ◽  
Energy Difference ◽  
Local Magnetic Moment ◽  
Face Centered Cubic ◽  
Elastic Parameters ◽  
Starting Point ◽  
Fcc Phase ◽  
Random Alloys

The single-crystal and polycrystalline elastic parameters of paramagnetic Fe0.6−xCr0.2Ni0.2Mx (M = Al, Co, Cu, Mo, Nb, Ti, V, and W; 0 ≤ x ≤ 0.08) alloys in the face-centered cubic (fcc) phase were derived by first-principles electronic structure calculations using the exact muffin-tin orbitals method. The disordered local magnetic moment approach was used to model the paramagnetic phase. The theoretical elastic parameters of the present Fe–Cr–Ni-based random alloys agree with the available experimental data. In general, we found that all alloying elements have a significant effect on the elastic properties of Fe–Cr–Ni alloy, and the most significant effect was found for Co. A correlation between the tetragonal shear elastic constant C′ and the structural energy difference ΔE between fcc and bcc lattices was demonstrated. For all alloys, small changes in the Poisson’s ratio were obtained. We investigated the brittle/ductile transitions formulated by the Pugh ratio. We demonstrate that Al, Cu, Mo, Nb, Ti, V, and W dopants enhance the ductility of the Fe–Cr–Ni system, while Co reduces it. The present theoretical data can be used as a starting point for modeling the mechanical properties of austenitic stainless steels at low temperatures.

scholarly journals Nitrogen Interstitial Alloying of CoCrFeMnNi High Entropy Alloy through Reactive Powder Milling

Entropy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 363 ◽  
Author(s):  
Igor Moravcik ◽  
Jan Cizek ◽  
Larissa Gouvea ◽  
Jan Cupera ◽  
Ivan Guban ◽  
...  
Keyword(s):  
Lattice Parameter ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
Simple Method ◽  
High Entropy ◽  
Plasma Sintering ◽  
Milling Duration ◽  
Face Centered ◽  
Fcc Phase ◽  
Reactive Powder

The present work is focused on the synthesis of CoCrFeMnNi high entropy alloy (HEA) interstitially alloyed with nitrogen via powder metallurgy routes. Using a simple method, nitrogen was introduced to the HEA from the protective N2 gas atmosphere during mechanical alloying (MA) processing. The lattice parameter and amount of nitrogen in HEA were observed to be linearly proportional to the milling duration. The limited solubility of nitrogen in the main face centered cubic (FCC) phase resulted in the in-situ formation of nitrides and, accordingly, significant increase in the hardness values. It has been shown that fabrication of such nitrogen-doped HEA bulk materials can be conveniently achieved by a simple combination of MA + spark plasma sintering processes, without the need for adding nitrogen from other sources.

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.

Lattice imaging of precipitates in Al-Zn-Mg alloy

1986 ◽  
Vol 44 ◽  
pp. 412-413
Author(s):  
C. K. Wu
Keyword(s):  
Grain Boundaries ◽  
Homogeneous Nucleation ◽  
Alloy System ◽  
Mg Alloy ◽  
List Type ◽  
Lattice Structures ◽  
Type Number ◽  
Orientation Relationships ◽  
Lattice Imaging ◽  
The Matrix

The precipitation phenomenon in Al-Zn-Mg alloy is quite interesting and complicated and can be described in the following categories:(i) heterogeneous nucleation at grain boundaries;(ii) precipitate-free-zones (PFZ) adjacent to the grain boundaries;(iii) homogeneous nucleation of snherical G.P. zones, n' and n phases inside the grains. The spherical G.P. zones are coherent with the matrix, whereas the n' and n phases are incoherent. It is noticed that n' and n phases exhibit plate-like morpholoay with several orientation relationship with the matrix. The high resolution lattice imaging techninue of TEM is then applied to study precipitates in this alloy system. It reveals the characteristics of lattice structures of each phase and the orientation relationships with the matrix.

scholarly journals Stability and equation of state of face-centered cubic and hexagonal close packed phases of argon under pressure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Agnès Dewaele ◽  
Angelika D. Rosa ◽  
Nicolas Guignot ◽  
Denis Andrault ◽  
João Elias F. S. Rodrigues ◽  
...  
Keyword(s):  
Equation Of State ◽  
Single Crystal ◽  
Single Crystal Sample ◽  
Moderate Pressure ◽  
Face Centered Cubic ◽  
Experimental Conditions ◽  
Crystal Sample ◽  
Hexagonal Close Packed ◽  
Face Centered ◽  
Fcc Phase

AbstractThe compression of argon is measured between 10 K and 296 K up to 20 GPa and and up to 114 GPa at 296 K in diamond anvil cells. Three samples conditioning are used: (1) single crystal sample directly compressed between the anvils, (2) powder sample directly compressed between the anvils, (3) single crystal sample compressed in a pressure medium. A partial transformation of the face-centered cubic (fcc) phase to a hexagonal close-packed (hcp) structure is observed above 4.2–13 GPa. Hcp phase forms through stacking faults in fcc-Ar and its amount depends on pressurizing conditions and starting fcc-Ar microstructure. The quasi-hydrostatic equation of state of the fcc phase is well described by a quasi-harmonic Mie–Grüneisen–Debye formalism, with the following 0 K parameters for Rydberg-Vinet equation: $$V_0$$ V 0 = 38.0 Å$$^3$$ 3 /at, $$K_0$$ K 0 = 2.65 GPa, $$K'_0$$ K 0 ′ = 7.423. Under the current experimental conditions, non-hydrostaticity affects measured P–V points mostly at moderate pressure ($$\le$$ ≤ 20 GPa).

High Temperature Mechanical Properties of Ni-Al-Cr Based Alloys with Refractory Alloying Elements

2006 ◽  
Vol 510-511 ◽  
pp. 358-361
Author(s):  
Won Yong Kim ◽  
Han Sol Kim ◽  
In Dong Yeo ◽  
Mok Soon Kim
Keyword(s):  
High Temperature ◽  
Volume Fraction ◽  
Lattice Parameter ◽  
Alloying Elements ◽  
Solid Solution Hardening ◽  
High Temperature Strength ◽  
High Temperature Mechanical Properties ◽  
Die Materials ◽  
The Matrix ◽  
Effective Role

We report on advanced Ni3Al based high temperature structural alloys with refractory alloying elements such as Zr and Mo to be apllied in the fields of die-casting and high temperature press forming as die materials. The duplex microstructure consisting of L12 structured Ni3Al phase and Ni5Zr intermetallic dispersoids was observed to display the microstructural feature for the present alloys investigated. Depending on alloying elements, the volume fraction of 2nd phase was measured to be different, indicating a difference in solid solubility of alloying elements in the matrix γ’ phase. Lattice parameter of matrix phase increased with increasing content of alloying elements. In the higher temperature region more than 973K, the present alloys appeared to show their higher strength compared to those obtained in conventional superalloys. On the basis of experimental results obtained, it is suggested that refractory alloying elements have an effective role to improve the high temperature strength in terms of enhanced thermal stability and solid solution hardening.

scholarly journals The Examination of Calcium ion Implanted Alumina with Energy Filtered Transmission Electron Microscopy

1997 ◽  
Vol 3 (S2) ◽  
pp. 413-414
Author(s):  
E.M. Hunt ◽  
J.M. Hampikian ◽  
N.D. Evans
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Pure Aluminum ◽  
Lattice Parameter ◽  
Face Centered Cubic ◽  
Ion Channeling ◽  
Transmission Electron ◽  
Knoop Microhardness ◽  
Aluminum Nanocrystals ◽  
Face Centered

Ion implantation can be used to alter the optical response of insulators through the formation of embedded nano-sized particles. Single crystal alumina has been implanted at ambient temperature with 50 keV Ca+ to a fluence of 5 x 1016 ions/cm2. Ion channeling, Knoop microhardness measurements, and transmission electron microscopy (TEM) indicate that the alumina surface layer was amorphized by the implant. TEM also revealed nano-sized crystals ≈7 - 8 nm in diameter as seen in Figure 1. These nanocrystals are randomly oriented, and exhibit a face-centered cubic structure (FCC) with a lattice parameter of 0.409 nm ± 0.002 nm. The similarity between this crystallography and that of pure aluminum (which is FCC with a lattice parameter of 0.404 nm) suggests that they are metallic aluminum nanocrystals with a slightly dilated lattice parameter, possibly due to the incorporation of a small amount of calcium.Energy-filtered transmission electron microscopy (EFTEM) provides an avenue by which to confirm the metallic nature of the aluminum involved in the nanocrystals.

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