Ordering and topologically close packed-phase precipitation in a Ni–25at.%Mo–5at.%Al alloy

Kulkarni, U.D.; Dey, G.K.

doi:10.1016/j.actamat.2004.02.019

Cited by 29 publications

(30 citation statements)

References 33 publications

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“…These have been the subject of considerable experimental and theoretical investigation over the last several years. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Much of this work pertains to the controversial issues related to the nature and the origin of the quenched in short-range ordered (SRO) state in Ni-rich binary alloys and to the evolution of the long-range ordered (LRO) phases from the state of SRO.…”

Section: Introductionmentioning

confidence: 99%

“…Another thermodynamics-based model [10,[15][16][17][18] views the state of SRO in binary Ni-Mo alloys as a delicate balance between the D0 22 and a hypothetical N 3 M phase. The latter phase, which has never been encountered in Ni-Mo-based alloys, occurs as a transitory phase in rapidly solidified Cu-Ti.…”

Section: Introductionmentioning

confidence: 99%

“…Both the structures are deemed to have a nearly equal stability in the binary Ni-Mo alloy. However, small additions of third elements such as Al [9,17] or Mn [21] can suitably alter the pair interaction energies (v i ) to make D0 22 more stable than the N 3 M structure. It is still not known what ternary addition will stabilize the N 3 M structure vis-a`-vis D0 22 .…”

Section: Introductionmentioning

confidence: 99%

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Monte Carlo Simulations of Ordering in Ni-Mo–Based Alloys

Kulkarni

2007

Metall Mater Trans A

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Monte Carlo simulation of the ordering processes in Ni-Mo-based alloys has been carried out with two distinct sets of pair interaction energies (v 1 to v 10 ). In the first case, where the D0 22 and the N 3 M structures have nearly equal stability, a state of short-range order showing intensity maxima at {1½0} and equivalent positions results. This is similar to what is observed in binary Ni 4 Mo alloy. When some of the pair interaction energies are changed to make D0 22 more stable than N 3 M, {100}, {110}, and equivalent maxima also appear. This is what is observed when small ternary additions of Al or Mn are made to Ni-Mo.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Monte Carlo Simulations of Ordering in Ni-Mo–Based Alloys

Kulkarni

2007

Metall Mater Trans A

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“…Therefore, it can be assumed that the composition of the alloy allows the formation of particles of such phases at certain temperatures. In the Mo-Al system, the Мо 3 Аl phase begins to form at temperatures of about 2150 °C [66]. So, it is possible to expect that in the Ni 75 Mo 20 Al 5 alloy, at temperatures above the liquidus, not only crystalline clusters of Mo atoms (formed as a result of the tendency to phase separation in the Ni / Mo diffusion couple), but also Mo 3 Al phase particles (formed as a result of the tendency to ordering in the Mo / Al diffusion couple) are present [61].…”

Section: Ni 75 Mo 20 Al 5 Alloymentioning

confidence: 99%

“…The authors assumed that the metastable phases play an important role in strengthening these alloys [65]. In the Ni-25 at% Mo-5 at.% Al alloy, Kulkarni and Dey have discovered and described in sufficient detail the coherent σ-Ni-Mо phase with H-phase plates in the form of wedgeshaped domains located between the grains of the phase [66]. It was believed that the σ-phase is the cause of degradation of mechanical properties of Ni-Al based alloys.…”

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Chemical Bond in Metallic Alloys: Electron Microscopic Study

Ustinovshikov¹

2017

NSTOA

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Aplastic anemia in systemic lupus erythematosus: A better prognosis acquired aplastic anemia Copyright: © 2016 Pannu and VarmaThe first experimental study to verify the existence of the high-temperature phase separation in alloys of the ironchromium system was undertaken by the example of the Fe-45% Cr alloy [15]. Using the method of TEM, it was found that the microstructure of this alloy after quenching from 1150 -1200°С was similar to that which had been obtained in Reference [14]. However, they interpreted such precipitations as chromium nitrides, i.e., as a kind of an "added" phase formed by the chemical reaction of chromium atoms (from the alloy) with atoms of nitrogen (from the air) during a high temperature heat treatment for quenching. A second study was conducted using the Fe 51 Cr 49 alloy, with the help of Mossbauer spectroscopy [16]. It is obvious that the choice of the method of research in Reference was poor, since it was hardly possible to judge a local phase separation of the alloy by the change of the partial gamma-resonance peaks corresponding to pure iron. Therefore, they did not manage to find the structure of phase separation [16]. Figure 2 shows the iron-rich part of an iron-chromium phase diagram, built on the results of electron microscopic studies of the microstructure of alloys of iron with 20, 30, 40 and 50 wt. % of chromium [17]. From the diagram, it can be seen that in the Fe-Cr system, there occur two phase transitions, in the result of which, for example, the microstructure that has formed as a consequence of the tendency to ordering is dissolving and a microstructure of phase separation is forming in its place (and vice versa). This occurs within the temperature ranges of 1100 -850°C and 600 -550°C (Figure 2) On the basis of these data, it could be concluded that at the level of microstructures, such a phase transition is bound to pass through the stage of the existence of the solid solution in the alloy. The authors have given this phase transition the name "orderingphase separation" [17]. Since the discovery of this transition, 17 binary systems have so far been studied and in 16 of them the transition has been experimentally found. The transition occurs at a temperature, specific for each system, at which the sign of the chemical interaction between atoms of A and B is reversed. It is obvious that the transformation of the microstructure formed as a result of the tendency to ordering into the microstructure formed as a result of the tendency to phase separation, and vice versa, is a consequence of the phase transition ordering -phase separation. The transition itself, that is, the process of changing the sign of the chemical interaction between dissimilar atoms, occurs at the level of changes in the electronic structure of the alloy.Before considering the physical essence of this transition, we would like to decide on the issue of the use of such terms as "ordering energy", "mixing energy", "enthalpy of mixing" and so on. Each of the above terms refers to basically the same no...

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