Creep at high temperatures in Ni-Fe alloys

The resistivity and absolute thermopower of a series of commercial f.c.c. Ni–Fe alloys containing 36–51 at. % Ni plus a comparison alloy of 75 at. % Ni have been measured over the range 1.5–125 K. Both the residual and the temperature dependent resistivities show a dramatic increase as the Ni concentration is reduced. By combining the present thermopower results with those at high temperatures by Kolomoets and Vedernikov, it is found that a pronounced maximum in the absolute magnitude of the thermopower occurs at a temperature of the order of 200–400 K. The results have been interpreted in terms of the 'weak ferromagnet' band model. Spin-mixing is briefly discussed and shown not to be of primary importance in these alloys.

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Heat Capacity of Decagonal and Icosahedral Quasicrystalline Phases at High Temperatures

Фізика і хімія твердого тіла ◽

10.15330/pcss.21.2.260-265 ◽

2020 ◽

Vol 21 (2) ◽

pp. 260-265

Author(s):

Yu. V. Syrovatko ◽

O. O. Levkovich

Keyword(s):

Heat Capacity ◽

High Temperatures ◽

Energy Characteristic ◽

Quasicrystalline Phase ◽

Temperature Range ◽

Icosahedral Phases ◽

Icosahedral Quasicrystalline Phase ◽

Fe Alloys ◽

Icosahedral Quasicrystalline ◽

Capacity Structure

The paper deals with the calculations of heat capacity of quasicrystalline decagonal Al69Co21Ni10 and icosahedral Al63Cu25Fe12 quasicrystalline phases of Al–Co–Ni and Al–Cu–Fe alloys, respectively. According to the Gruneisen law, heat capacity is an energy characteristic, which reflects the phases’ resistance to failure. For calculations of the heat capacity, structure of quasicrystalline phases is considered in the model representation of anisotropic crystals. As a result, it is found that the heat capacity of quasicrystalline phases at high temperatures is the excessive one, i.e. it exceeds the Dulong-Petit value. Therefore, quasicrystalline phases at high temperatures are more stable, than the crystalline phase. For the decagonal quasicrystalline phase, heat capacity is more than 3R in the temperature range of ~480–1500 К, and for the icosahedral quasicrystalline phase – in the temperature range of ~380–1120 К. It follows that decagonal phases remain stable at high temperatures at which the icosahedral phases are destroyed.

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Tensile Properties of High Cr-Fe Alloys with Small Amounts of C and N, Annealed at High Temperatures

Tetsu-to-Hagane ◽

10.2355/tetsutohagane1955.63.8_1331 ◽

1977 ◽

Vol 63 (8) ◽

pp. 1331-1339

Author(s):

Tetsumori SHINODA ◽

Tadahisa NAKAMURA

Keyword(s):

Tensile Properties ◽

High Temperatures ◽

C And N ◽

Fe Alloys

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In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087616 ◽

1991 ◽

Vol 49 ◽

pp. 660-661

Author(s):

Z. L. Wang ◽

J. Bentley

Keyword(s):

High Temperatures ◽

Image Resolution ◽

Atomic Processes ◽

Crystal Surfaces ◽

Beam Radiation ◽

Surface Areas ◽

Transmission Electron ◽

Reflection Electron Microscopy ◽

Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

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