Alloy Vacuum Research Articles

The kinetics of thin film resistor stabilisation

Thin film resistors are manufactured by photolithography methods, using a nickel-chromium alloy vacuum deposited on a ceramic substrate. In order to stabilise the resistors, a high temperature heat treatment in an air furnace is undertaken, during which the resistors are partially oxidised. It was found that the extent of reaction can be expressed as p = 6 × 1 0 4 exp ⁡ ( − 7400 / T ) t 1 3 A temperature of 325°C is recommended for practical applications. It involves a 30% resistance increase after an hour, while standard deviation is less than 2%.

A comparison of outgassing rate of 304 stainless steel and A6063-EX aluminum alloy vacuum chamber after filling with water

Outgassing rates of A6063-EX aluminum alloy and SUS 304 stainless steel, in the form of a vacuum chamber, before and after filling the chambers with water were compared. The results showed that the outgassing rate of the aluminum alloy was greater than that of the stainless steel before baking. However, after in situ vacuum bakeout, the outgassing rate of the aluminum alloy became lower than that of the stainless steel, even for the chamber which had been filled with water. The Auger depth profile analysis reveals that the surface of the aluminum alloy, before bakeout, may have a porous aluminum oxide layer which increases the amount of the adsorbed gas molecules resulting in a large outgassing rate.

Cyclic crack resistance of magnesium alloys in vacuum and moist and highly dried air

Cyclic crack resistance of magnesium alloys in vacuum and moist and highly dried air

Fatigue crack growth and crack closure of P/M Al-Si-Fe alloy in air and in vacuum.

Fatigue crack growth tests were carried out on P/M (Powder Metallurgy) Al-Si-Fe alloy in vacuum and in air under ΔK-increasing and-decreasing conditions, and crack growth rates and crack closure behavior were investigated in detail by using the unloading elastic compliance method. The effect of anisotropy of the material due to extrusion process on crack growth characteristics was also examined. Fatigue crack growth resistance in terms of ΔK and ΔKeff was usually increased in a vacuum. The degree of increase, however, was found to depend on crack growth direction in relation to the anisotropy of the material and on crack growth rate regime. Crack opening point was different between material anisotropy directions but could well be correlated to the roughness of fracture was dominant in air, while that in vacuum was found to take similar values irrespective of material anisotropy directions and of macroscopic appearance of the fracture surface.

Aluminum alloy ultrahigh vacuum system for molecular beam epitaxy

As a research project for aluminum alloy molecular beam epitaxy systems, a large aluminum alloy chamber with a special surface finish was constructed. Its outgassing rate and ultimate pressure were measured. The special surface finish was analyzed using Auger electron spectroscopy. The oxide layer on the aluminum alloy was about 40 A thick. The outgassing rate before baking was measured as 10−11 Torr l/s cm2, and the rate after baking (150 °C, 24 h) was 3×10−13 Torr l/s cm2. This value is approximately one to two orders of magnitude lower than that of a stainless‐steel chamber, such as SUS 304. The ultimate pressure was 7×10−11 Torr when pumped with a turbomolecular pump and an ion pump. With addition of the newly developed titanium sublimation pump, the ultimate pressure was 6×10−12 Torr (6.5×10−12 mbar). This ultimate pressure is very low for a large aluminum alloy vacuum chamber. Ceramic coating of SiO2 using a spark discharge in a silicate solution on aluminum alloy was not corroded by gallium. This c...

アルミニウム合金真空チェンバーのガス放出率 ＩＶ

アルミニウム合金真空チェンバーのガス放出率 ＩＶ

Thermal outgassing from aluminum alloy vacuum chambers

A special aluminum alloy tube, primarily A6063 alloy clad inside with A1050 al pumpdown at room temperature and ∼1×10−13 Torr⋅l/s cm2 10 h after a 1 day bakeout at 150 °C. When the tube was vented to air for 1 day, the vacuum performance was not degraded. Outgassing rates for another type of tube, made of A6063 alloy but using a special extrusion method, were measured for several cases: (1) after exposure to air for about 1.5 years, (2) after partially filled with water for 1 day, and (3) after partially filled with water for 1 week. The outgasssing rate 10 h after baking was ∼1.5×10−13 Torr⋅l/s cm2 for case (2) and <5×10−13 Torr⋅l/s cm2 for case (3). Some surface parameters, adsorption isotherms, surface coverages, mean residence times, and adsorption energies were calculated to describe the surface conditions for all the above cases.

Development and Testing of Bumper Limiter of Aluminum Alloy Vacuum Vessel for Reacting Plasma Experiment

Two types of graphite bumper limiters were designed and trially fabricated for a reacting plasma device, R-tokamak. High heat load tests were conducted to examine thermal behavior and thermal shock resistance of the limiters by using a 100kW electron beam facility. The experimental data were compared with the results of 3-D thermal analysis.

Kinetics of the processes of gas impregnation and sublimation of titanium alloys in vacuum at temperatures of 1123 and 1273�K

This paper studies the kinetics of the processes of interaction of titanium alloys with the residual gases of a vacuum and reveals their influence on the structure of the surface layers of titanium alloys. Aluminum, cannot sublimate since it possesses the greatest affinity for oxygen among the alloy elements, and titanium and zirconium, judging from the pressure of the staturated vapors of the pure metals and their oxides, cannot sublimate because of the low values of the parameters. An increase in temperature to 1273 degrees K does not qualitatively change the character of interaction of PT-7M, PT3V, VT6S, and OT4-1 alloys with the residual gases of the vacuum, but intensifies these processes. In VT5-1, a qualitative change in the processes as the result of activation of sublimation of tin from the alloy is observed.

Outgassing rate of aluminum alloy vacuum chamber for tristan ultra-high vacuum system.

The TRISTAN Electron Positron Colliding Ring consists of a main ring of 30GeV (e-, e+) with a diameter of approx. 1000m, and a subordinate ring of 6-8GeV (e-, e+) with a diameter of approx. 100m for preacceleration and storage. Both rings require a pressure of approx. 10-9 Torr at Beam On and a pressure of approx. 10-10 Torr at Beam Off, respectively.Considering the effect of beam on the vacuum, the chamber is made of aluminum alloy with a high cooling efficiency because the inner walls are exposed to very powerful radiation (3kW/m (approx. 100W/cm2)). Generally, aluminum alloy with a high outgassing rate has been thought of as unsuitable for ultra-high vacuum material. A newly developed aluminum alloy produced by special extrusion, however, shows an outgassing rate in the order of 10-14 Torr l/s·cm2 due to 24-hour baking at 150°C. Also, the residual radioactivity in the aluminum new alloy is noticeably reduced, compared with stainless steel. The above-mentioned facts prove that this alloy is excellent as ultra-high vacuum material.As a result of the experiment using the aluminum alloy in all vacuum parts it is confirmed that, contrary to the conventional view, aluminum alloy is most suitable for ultra-high vacuum material and that the TRISTAN Ring in which the alloy is used can be operated with a satisfactory performance.

An aluminum vacuum vessel for a low radioactivity fusion device in near future D-T experiment

Use of a low radioactivity fusion device has been proposed for a near future D-T experiment in an R-tokamak design by the Institute of Plasma Physics, Nagoya University, in order to avoid the difficulties of repair and maintenance by remote handling. The radioactivity in the aluminum alloy design is smaller by a factor of 20–70 than that in the Phase 1 design (an initial design for this project) where a stainless steel vacuum vessel is employed. In this paper the mechanical, thermal and electric properties are compared to those of the stainless steel vacuum vessel. The electromagnetic performances are analyzed, and stress and buckling analysis is performed in both designs. The problems and advantages of the aluminum alloy vacuum vessel are shown in this study. In the results, the aluminum vacuum vessel is feasible as the component for the low radioactivity fusion device.

Deoxidation of high-melting-point metals and alloys in vacuum

Through melting, refractory metals and alloys are becoming important for use as structural materials. Vacuum-melting is considered to be able to provide high-purity ingots because of its purifying effect, particularly the effect of evaporation deoxidation via volatile oxides. Thermodynamic calculation leads us to predict a limited possibility for deoxidizing Ti, Zr, Hf, a good possibility for Mo and W, and an intermediate possibility for V, Nb, and Ta. The sponges of these metals containing oxygen were degassed under high vacuum at temperatures below or over the melting point, and the change in oxygen content was measured as a function of time. The observed rates of purification agreed well with the thermodynamically estimated deoxidizing tendencies. Kinetic analysis of the degassing curves obtained for the Nb-O, Ta-O, Mo-O, and W-0 alloys showed that the rate-determining step was the diffusion of oxygen in the metal or the recombination of oxygen with the base metal atoms and the transfer of the molecules into the vacuum. If carbon was present in the metal, the oxygen liberation was considerably accelerated. However, an excess of oxygen to carbon was necessary for the carbon level to be sufficiently lowered at the same time.

Outgas of the Aluminum Alloy Vacuum Chamber

Outgas of the Aluminum Alloy Vacuum Chamber

New All Aluminum Alloy Vacuum System for the TRISTAN e+e- Storage Accelerator

A new all aluminum alloy vacuum system for TRISTAN e+e- storage accelerator is described. The system is designed to satify such conditions as high reliability, simplicity, low residual radioactivity, impedance matching, low space factor, light weight, standerdization of the components and low cost. Aluminum alloy is chosen to be as material of the vacuum system. The construction of the accumulator ring starts from April 1981.

Fatigue crack growth and the plastic zone in air and in vacuum

1. It has been observed that the fatigue crack growth macrorate dl/dN in Cu−7.5% Al is related to the depth of the microscopic plastic zone h by an exponential relationship of the form $$\frac{{dl}}{{dN}} = Bh^p $$ where B and p are constants in a certain range of zone depth dependent upon medium. The critical zone depth hcr corresponding to the break on the crack growth rate curve is 2.5–3 grain diameters in both media. 2. In the initial period of crack growth, when the depth of the plastic zone has not reached hcr, the microrate exceeds the macrorate, i.e., a striation is formed not in each load cycle but in the last of a series of cycles. This is characteristic of a fatigue crack in both media but in vacuum the differences between micro- and macrorates are greater than in air. When the plastic zone exceeds the value of hcr the macrorate becomes equal to the microrate, i.e., a striation occurs in each load cycle. 3. Fatigue crack growth in Cu−7.5% Al alloy in vacuum occurs by the formation of striations which are just as clear and regular as in air. In AMg6 alloy distinct striations appear in vacuum only at low temperature. This confirms the fact that the formation of fatigue striations is not the result of action of the air medium. 4. A hypothesis is stated that the formation of striations in fatigue crack growth occurs with a limited plastic zone size and is dependent upon the mechanism of their formation during relaxation of stresses requiring a certain degree of elastic restraint of plastically deformed microvolumes.

Investigation of mullite-corundum nozzles after service melting nickel alloys in vacuum

Investigation of mullite-corundum nozzles after service melting nickel alloys in vacuum

Fatigue fracture of some magnesium alloys in vacuum at room and low temperatures

Fatigue fracture of some magnesium alloys in vacuum at room and low temperatures

Bakable aluminium vacuum chamber and bellows with an aluminum flange and metal seal for ultrahigh vacuum

A bakable (200°C) aluminium alloy vacuum chamber and bellows (6063-T6) with an aluminium alloy (2219-T87) flange and metal seal (Helicoflex-HN: aluminium O-ring) has been constructed. Such components may be used in the assemblies of the vacuum chambers in proton synchrotrons and electron storage rings.

電子ストーレジリングのためのアルミニウム‐ステンレス鋼接合ビームダクト

Friction welding has been developed at KEK to join aluminium alloy vacuum chambers to stainless steel vacuum components of an electron storage ring. The stainless steel surface is electroplated with silver to a thickness of 10 μm before welding. Additional procedures such as complicated pre-treatment for electroplating, various heat treatment and various cleaning procedures are not required. Fabricated transitions up to 100 mm in diameter have been obtained. Some units have been tested for mechanical and vacuum leak properties as beam ducts. It has been found that the strength of the bonding plane is very strong and fracture of the tensile specimens occurs not at the bonded plane but at the aluminium alloy part, and that vacuum leak does not occur for heat cycles up to 200°C. Welds torerate thermal shock to liquid nitrogen temperature and remain leak-tight.

The effect of irradiation on the fatigue and flow behavior of TZM alloy

The pre- and postirradiation fatigue and flow properties of the molybdenum-base alloy TZM have been determined at 427°C. Neutron irradiation to a fluence of 1 × 10 22 n/cm 2 > 0.1 MeV increased the fatigue life of the stress relieved alloy in vacuum by approximately a factor of two in the strain range of 0.11 to 0.18%. The environmental effect of gaseous impurities on the rate of fatigue crack growth in unirradiated TZM was investigated for air pressures from approximately 10 −4 to 10 0 Pa. Compressive now properties were determined at 427°C at a strain rate of 1 × 10 −3 sec −1 and at 500°C for a range of strain rates. Irradiation to a fluence of 1.2 × 10 22 n/cm 2 increased the yield strength of stress relieved TZM by about 50 percent. The ductile to brittle transition temperature appeared to be between 427 and 500°C at a compressive strain rate of 1 × 10 −3 sec −1. Irradiation induced changes in microhardness and yield strength were correlated with TEM results using general hardening models.