Rates of Evaporation in a Vacuum in Liquid Ni-Ti Alloys.

Ogasawara, Yoshihito; Hadi, Tabaian Seyed; Maeda, Masafumi

doi:10.2355/isijinternational.38.789

Cited by 20 publications

(11 citation statements)

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“…Also, the temperature measurements are reliable. A majority of the measurements on the evaporation rates of Si, Ni, and Ti in the electron beam vacuum furnace [25] are greater than the calculated theoretic rates. The temperatures are probably higher than those predicted in the calculations of the temperature.…”

Section: Evaporation Rate Of Pure Metalsmentioning

confidence: 81%

“…The S values corresponding to the measured p/p°values [22][23][24][25] were determined by Eq. [16] for g = 1.0 and by Eq.…”

Section: ½22mentioning

confidence: 99%

“…As mentioned before, the melt surface temperature is reduced due to the heat losses from the = 1) vs the experimental measurements in the literature. [22][23][24][25] Zn data are from unit values; only bulk melt temperature is measured. surface and the endothermic evaporation reaction at the surface.…”

Section: Evaporation Rate Of Pure Metalsmentioning

confidence: 99%

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Vacuum Evaporation of Pure Metals

Safarian

Engh

2012

Metall Mater Trans A

116

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Theories on the evaporation of pure substances are reviewed and applied to study vacuum evaporation of pure metals. It is shown that there is good agreement between different theories for weak evaporation, whereas there are differences under intensive evaporation conditions. For weak evaporation, the evaporation coefficient in Hertz-Knudsen equation is 1.66. Vapor velocity as a function of the pressure is calculated applying several theories. If a condensing surface is less than one collision length from the evaporating surface, the Hertz-Knudsen equation applies. For a case where the condensing surface is not close to the evaporating surface, a pressure criterion for intensive evaporation is introduced, called the effective vacuum pressure, p eff . It is a fraction of the vapor pressure of the pure metal. The vacuum evaporation rate should not be affected by pressure changes below p eff , so that in lower pressures below p eff , the evaporation flux is constant and equal to a fraction of the maximum evaporation flux given by Hertz-Knudsen equation as 0.844 _ n Max . Experimental data on the evaporation of liquid and solid metals are included.

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Section: Evaporation Rate Of Pure Metalsmentioning

confidence: 81%

“…The S values corresponding to the measured p/p°values [22][23][24][25] were determined by Eq. [16] for g = 1.0 and by Eq.…”

Section: ½22mentioning

confidence: 99%

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Vacuum Evaporation of Pure Metals

Safarian

Engh

2012

Metall Mater Trans A

116

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“…The evaporation coefficient is a physical parameter that is defined as a ratio of free evaporation and equilibrium fluxes and describes the kinetic energy barrier to evaporation. In liquid metals, the value of γ i is close to 1. − However, in silicate melts, γ i is often less than one, as was measured for Si evaporating from molten SiO 2 . , …”

Section: Theoretical Frameworkmentioning

confidence: 83%

Loss and Isotopic Fractionation of Alkali Elements during Diffusion-Limited Evaporation from Molten Silicate: Theory and Experiments

Zhang

Nie

Mendybaev

et al. 2021

ACS Earth Space Chem.

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Moderately volatile elements (MVEs) are variably depleted in planetary bodies, reflecting the imprints of nebular and planetary processes. Among MVEs, Na, K, and Rb are excellent tracers for unraveling the history of MVE depletion in planetary bodies because they have similar geochemical behaviors but can be chemically fractionated by evaporation and condensation processes. Furthermore, K and Rb are amenable to high-precision isotopic analyses, which can help constrain the conditions of evaporation and condensation. To quantitatively understand why Na, K, and Rb are depleted in planetary bodies, we have carried out vacuum evaporation experiments from basaltic melt at 1200 and 1400 °C to study their evaporation kinetics and isotopic fractionations. We chose this composition because it is relevant to evaporation from small differentiated planetesimals. The Rb isotopic compositions of the evaporation residues were measured by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS), and the K isotopic compositions were measured along profiles across the residues by secondary ion mass spectrometry (SIMS). In the 1400 °C run products, we found that the concentrations of both K and Rb in the run products decreased from core to rim, which was accompanied by a heavy K isotope enrichment near the surface. This indicates that, in this run, evaporation was limited by diffusion. To use those data quantitatively, we derive analytical equations that describe the evaporation rate and isotopic fractionation associated with diffusion-limited evaporation from a sphere, slab, and cylinder in transient and quasi-steady state regimes. This model is used to tease out the roles that diffusive transport in the melt and evaporation at the melt/gas interface play in setting the elemental depletion and isotopic composition of the residue. Under our experimental conditions, volatility decreases in the order of Na, Rb, and K. Using our experimental results in a thermodynamic model, we have estimated the product γΓ of activity coefficients × evaporation coefficients of Na, Rb, and K. The measured isotopic compositions of the residues are well explained using Rayleigh distillations, whereby the relative volatilities of K and Rb isotopes are given by the square root of their masses. We use our results and previously published data to predict how K and Rb could have been lost as a function of temperature, melt composition, oxygen fugacity, and saturation degree relevant to Vesta's building blocks. We find that the K and Rb depletions, K/Rb elemental fractionation, and δ 41 K and δ 87 Rb isotopic fractionations of Vesta (as sampled by howardite-eucrite-diogenite (HED) meteorites) are best explained by evaporation of submillimeter size objects for 0.1−10 years at moderate temperatures (∼1050 °C) in a medium ∼98.8% saturated.

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“…One should keep in mind that Ni evaporation during NiTi alloys processing is a problem widely reported in the literature. [13][14][15][16][17] However, one may take advantage of this phenomenon to produce graded parts with EBF3; compositional fluctuations can be intentionally added to enable a graded mechanical, physical, or chemical behavior. 18,19 Figure 4(b) exhibits coarse columnar grains in the build/height direction.…”

Section: Resultsmentioning

confidence: 99%

The electron beam freeform fabrication of NiTi shape memory alloys. Part I: Microstructure and physical–chemical behavior

Guimarães

Pixner

Trimmel

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part L:

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Nickel–titanium alloys are the most widely used shape memory alloys due to their outstanding shape memory effect and superelasticity. Additive manufacturing has recently emerged in the fabrication of shape memory alloy but despite substantial advances in powder-based techniques, less attention has been focused on wire-based additive manufacturing. This work reports on the preliminary results for the process-related microstructural and phase transformation changes of Ni-rich nickel–titanium alloy additively manufactured by wire-based electron beam freeform fabrication. To study the feasibility of the process, a simple 10-layer stack structure was successfully built and characterized, exhibiting columnar grains and achieving one-step reversible martensitic–austenitic transformation, thus showing the potential of this additive manufacturing technique for processing shape memory alloys.

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Rates of Evaporation in a Vacuum in Liquid Ni-Ti Alloys.

Abstract: SamplePreparationThe starting materials were electrolytic nickel (99.9 masso/o) and purified titanium (99.7masso/o). Oxygen contents were below 20massppm for nickel and about 400800 massppm

Cited by 20 publications

References 0 publications

Vacuum Evaporation of Pure Metals

Vacuum Evaporation of Pure Metals

Loss and Isotopic Fractionation of Alkali Elements during Diffusion-Limited Evaporation from Molten Silicate: Theory and Experiments

The electron beam freeform fabrication of NiTi shape memory alloys. Part I: Microstructure and physical–chemical behavior

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