Thermal diffusivity of olivine single crystals and a dunite at high temperature: Evidence for heat transfer by radiation in the upper mantle

In order to determine the thermal diffusivity of materials, especially solids and liquids at high temperatures, two extended containerless flash techniques that are applicable to levitated spherical specimen are proposed. The extended flash methods are modeled as an axisymmetric transient conduction heat transfer problem within the sphere. For the “single-step” method, analytic expressions for the temperature history on the surface of the sphere are obtained that are independent of the incident energy and the absorption layer thickness. It is shown that by knowing the sample diameter and recording the temperature transient history at least at two different points on the surface simultaneously, the thermal diffusivity can be determined. A detailed discussion of the effects of the various parameters is presented. For the “two-step” analysis the problem of nonlinearity of the radiative heat transfer boundary condition is overcome by replacing it with the measured time-dependent surface temperature data. Upon obtaining the temperature field the determination of the thermal diffusivity turns into a minimization problem. In performing the proposed two-step procedure there is a need to undertake a cool-down experiment. Results of an experimental study directed at determining the thermal diffusivity of high-temperature solid samples of pure Nickel and Inconel 718 superalloy near their melting temperatures using the single-step method are discussed. Based on close agreement with reliable data available in the literature, it is concluded that the proposed techniques can provide reliable thermal diffusivity data for high-temperature materials.

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The Role of Heat Transfer by Radiation in High-Temperature Reaction Synthesis of NiAl Intermetallide

Powder Metallurgy and Metal Ceramics ◽

10.1007/s11106-017-9908-2 ◽

2017 ◽

Vol 56 (7-8) ◽

pp. 393-398

Author(s):

K. M. Petrash ◽

V. V. Skorokhod ◽

V. P. Solntsev ◽

T. O. Solntseva

Keyword(s):

Heat Transfer ◽

High Temperature ◽

Reaction Synthesis ◽

Temperature Reaction ◽

High Temperature Reaction ◽

Heat Transfer By Radiation

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High temperature thermal diffusivity of Ni3Al and nickel-based superalloy single crystals

Scripta Metallurgica et Materialia ◽

10.1016/0956-716x(93)90077-6 ◽

1993 ◽

Vol 28 (4) ◽

pp. 423-428 ◽

Cited By ~ 2

Author(s):

P. Archambault ◽

A. Hazotte

Keyword(s):

High Temperature ◽

Thermal Diffusivity ◽

Single Crystals ◽

Nickel Based Superalloy

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Precipitation of NiHfsi phase in NiAl single crystals containing Hf

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100139032 ◽

1995 ◽

Vol 53 ◽

pp. 532-533

Author(s):

A. Garg ◽

R. D. Noebe ◽

R. Darolia

Keyword(s):

High Temperature ◽

Single Crystals ◽

High Temperature Strength ◽

Bridgman Technique ◽

Shell Mold ◽

Third Phase ◽

Unknown Phase ◽

Transmission Electron ◽

Two Phases ◽

Nial Matrix

Small additions of Hf to NiAl produce a significant increase in the high-temperature strength of single crystals. Hf has a very limited solubility in NiAl and in the presence of Si, results in a high density of G-phase (Ni16Hf6Si7) cuboidal precipitates and some G-platelets in a NiAl matrix. These precipitates have a F.C.C structure and nucleate on {100}NiAl planes with almost perfect coherency and a cube-on-cube orientation-relationship (O.R.). However, G-phase is metastable and after prolonged aging at high temperature dissolves at the expense of a more stable Heusler (β'-Ni2AlHf) phase. In addition to these two phases, a third phase was shown to be present in a NiAl-0.3at. % Hf alloy, but was not previously identified (Fig. 4 of ref. 2 ). In this work, we report the morphology, crystal-structure, O.R., and stability of this unknown phase, which were determined using conventional and analytical transmission electron microscopy (TEM).Single crystals of NiAl containing 0.5at. % Hf were grown by a Bridgman technique. Chemical analysis indicated that these crystals also contained Si, which was not an intentional alloying addition but was picked up from the shell mold during directional solidification.

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