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Title: On the existence of declared 9R phase in Fe–Ni invar alloy

Abstract

An analysis of recently reported electron diffraction patterns suggests that metastable austenitic Fe–32Ni alloy subjected to α → γ transformation upon slow heating does not exhibit any signs of formation of the 9R phase; the conventional nanocrystalline γ phase with an fcc lattice is formed instead. Extended lamellae with a layered structure, erroneously identified as a new phase of the (3R + 9R) type in Fe–32Ni alloy, are conventional twinning (midrib) regions of each initial α crystal, in which γ-phase twin nanolamellae are formed upon heating.

Authors:
; ;  [1]
  1. Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)
Publication Date:
OSTI Identifier:
22645442
Resource Type:
Journal Article
Resource Relation:
Journal Name: Crystallography Reports; Journal Volume: 61; Journal Issue: 4; Other Information: Copyright (c) 2016 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; AUSTENITIC STEELS; CRYSTAL STRUCTURE; CRYSTALS; ELECTRON DIFFRACTION; FCC LATTICES; INVAR; LAMELLAE; NANOSTRUCTURES; TWINNING

Citation Formats

Kabanova, I. G., Sagaradze, V. V., E-mail: vsagaradze@imp.uran.ru, and Kataeva, N. V. On the existence of declared 9R phase in Fe–Ni invar alloy. United States: N. p., 2016. Web. doi:10.1134/S1063774516040088.
Kabanova, I. G., Sagaradze, V. V., E-mail: vsagaradze@imp.uran.ru, & Kataeva, N. V. On the existence of declared 9R phase in Fe–Ni invar alloy. United States. doi:10.1134/S1063774516040088.
Kabanova, I. G., Sagaradze, V. V., E-mail: vsagaradze@imp.uran.ru, and Kataeva, N. V. 2016. "On the existence of declared 9R phase in Fe–Ni invar alloy". United States. doi:10.1134/S1063774516040088.
@article{osti_22645442,
title = {On the existence of declared 9R phase in Fe–Ni invar alloy},
author = {Kabanova, I. G. and Sagaradze, V. V., E-mail: vsagaradze@imp.uran.ru and Kataeva, N. V.},
abstractNote = {An analysis of recently reported electron diffraction patterns suggests that metastable austenitic Fe–32Ni alloy subjected to α → γ transformation upon slow heating does not exhibit any signs of formation of the 9R phase; the conventional nanocrystalline γ phase with an fcc lattice is formed instead. Extended lamellae with a layered structure, erroneously identified as a new phase of the (3R + 9R) type in Fe–32Ni alloy, are conventional twinning (midrib) regions of each initial α crystal, in which γ-phase twin nanolamellae are formed upon heating.},
doi = {10.1134/S1063774516040088},
journal = {Crystallography Reports},
number = 4,
volume = 61,
place = {United States},
year = 2016,
month = 7
}
  • Polarized neutron scattering experiments have been performed on an Fe/sub 65/Ni/sub 35/ Invar alloy in the paramagnetic phase at T = 1.25T/sub c/. Constant-q spectra were fitted to simple Lorentzian functions and the q-dependence of the half-width GAMMA was found to agree with that of the spin-diffusion model in the measured q range (0.1 A/sup -1/
  • The through-mask electrochemical micromachining of invar (Fe-36Ni) alloy film in 4M NaCl solution was carried out. Wall profile change during electrochemical etching was simulated using the boundary element method with assumptions of negligible concentration variation in the bulk solution and kinetic resistance at the electrode surface. The shape evolution with time was predicted and agreed well with the experimental values for small aspect ratio.
  • It is well established that Fe-Ni invar alloys have low strength. As it was shown in the previous paper additions of small amounts (about 1 wt.%) Be lead to age-strengthening of these alloys without a significant increase in their linear thermal expansion coefficient (LTEC). The optimal combination of nickel and beryllium in the ternary Fe-Ni-Be alloys has been determined (40 wt.% Ni and 0.8 wt.%Be) to permit an increase in hardness upon aging (at 550 C) while maintaining LTEC at the low level. The aim of the present work is to study the temperature dependence of the LTEC and mechanicalmore » properties of Fe-Ni-Be alloy with the optimal composition.« less
  • To assess the metallurgical reasons for the susceptibility of Invar Fe-36Ni alloy to reheat cracking, a number of specimens have been prepared and welded in a weld simulator, with a gas tungsten arc welding procedure and heat inputs ranging from 1.3 to 7.5MJ/m. Grain coarsening in the heat affected zone was predicted with fair accuracy by using a diffusive model. Samples with two beads-on-plate were used to study the effect of reheating of the first bead by the weld thermal cycle of the second pass. Grain-boundary migration was found to be sensitive to boundary orientation and morphology. Filler metal containingmore » Ti-Mn was responsible for the further impeding of boundary migration owing to the presence of precipitates. A clean surface and the use of oxygen-free shielding gas were compulsory requirements to obtain sound weldments; otherwise preferential diffusion of oxygen along grain boundaries and subsurface inclusions were observed in the joint.« less
  • We have succeeded in increasing up to 150 K the Curie temperature in the Fe{sub 64}N{sub 36}6 invar alloy by means of a severe mechanical treatment followed by a heating up to 1073 K. The invar behavior is still present as revealed by the combination of magnetic measurements with neutron and x-ray techniques under extreme conditions, such as high temperature and high pressure. The proposed explanation is based in a selective induced microstrain around the Fe atoms, which causes a slight increase in the Fe-Fe interatomic distances, thus reinforcing ferromagnetic interactions due to the strong magnetoelastic coupling in these invarmore » compounds.« less