ADVANCES IN CRYOGENIC ENGINEERING: Transactions of the International Cryogenic Materials Conference - ICMC
711(2004); http://dx.doi.org/10.1063/1.1774545View Description Hide Description
On the basis of a thermodynamic approach the magnetocaloric effect (MCE) arising at the first order transition in the heavy rare earth metals Tb, Dy, Er and Tb0.5Dy0.5 alloy is considered. The main contributions to the MCE (exchange, magnetoelastic, anisotropic and that due to magnetic energy) were calculated in the temperature interval corresponding to the first order transition. It was shown that the model adequately describes the MCE and gives results which are in accord with direct experimental measurements.
711(2004); http://dx.doi.org/10.1063/1.1774546View Description Hide Description
The New Energy and Industrial Technology Development Organization (NEDO) in Japan has built a project called World Energy Network (WE‐NET). The aim of WE‐NET is development of a new infrastructure of hydrogen technology for the upcoming hydrogen energy society. Among several element technologies to be achieved, high efficient liquefaction and storage of hydrogen have been identified as key technologies. Active Magnetic Regenerative Refrigeration (AMRR) is thought to have the best performance in cooling efficiency for hydrogen liquefaction. AMRR makes use of magnetic materials so that a magnetic field can create the cooling power. Therefore, magnetic and thermal properties of the materials are of crucial importance to the design and development of the AMRR system. In this paper, we focused specially on thermal expansion among the thermal properties of magnetic materials for AMRR to provide a fundamental database for the design of the AMRR. Correlation between magnetic property and thermal expansion of the Gd5(Six Ge 1−x)4 system is also examined.
711(2004); http://dx.doi.org/10.1063/1.1774547View Description Hide Description
The effect of niobium content on shape memory characteristics in (Ni 47Ti44)100−x Nb x (at.%) alloys (x=3,9,15,20,30) was investigated in detail by performing differential scanning calorimetry and cryogenic tensile tests at a temperature of (Ms +30 K). The results show that tensile strain as much as 6% vanished completely in five alloys after unloading and then heating to 473K. But with increasing the deformation, substantial plastic deformation that was irreversible occurred in the niobium‐rich phase. As a result, the residual elongation increased. Moreover, the degradation of the shape recovery ratio increased with increasing niobium content. It was also found that the transformation hysteresis was widened by deformation. The effect of niobium content on the transformation hysteresis and shape memory effect was investigated systematically and the related mechanism has been proposed based on microstructural analysis. In view of the engineering application, where wide hysteresis and better shape memory effect is desired, the optimized niobium content is proposed.
711(2004); http://dx.doi.org/10.1063/1.1774548View Description Hide Description
Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumulated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation functions, by inherently sensing a change in temperature and actuating by undergoing a shape change as a result of a temperature‐induced phase transformation. Two aspects of our work on cryogenic SMAs are addressed here. First — a shape memory alloy based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil‐off systems for advanced spaceport applications. Second — fabrication via arc‐melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed.
711(2004); http://dx.doi.org/10.1063/1.1774549View Description Hide Description
The low temperature volumetric heat capacity (∼3.5 to 350 K) and magnetic susceptibility (∼4 to 320 K) of Er3Rh, Er3Ir, Er3Pt, Er2Al, and Er2Sn have been measured. All of the compounds order antiferromagnetically (or ferrimagnetically), and most exhibit more than one magnetic ordering transition. The volumetric heat capacities in general are smaller than those of the prototype magnetic regenerator materials, except for Er3Ir in the 12 to 14 K temperature range.
711(2004); http://dx.doi.org/10.1063/1.1774550View Description Hide Description
We compared methods of measuring the residual resistivity ratio (RRR) of high‐purity Nb using transport current. Our experimental study is intended to answer some fundamental questions about the best measurement method for RRR and the biases that may exist among different measurement methods, model equations, and magnetic field orientations. Two common ways to obtain the extrapolated normal‐state resistivity at 4.2 K are (1) measure the normal‐state resistivity as a function of field at 4.2 K and extrapolate to zero field and (2) measure the normal‐state resistivity as a function of temperature in zero field and extrapolate to 4.2 K. Both approaches have their associated difficulties. We also compared data taken with the magnetic field both parallel and transverse to the specimen current and we measured magnetoresistance at various temperatures from 4 to 16 K. We combined all of these data to estimate the RRR using an approach based on the Kohler empirical rule regarding magnetoresistance. The Kohler rule imposes the shape of the magnetoresistance curve at the higher temperatures to better predict the extrapolated normal‐state values at the lower temperatures.
A Fully Automatic Press for Mechanical and Electrical Testing of Full‐Size ITER Conductors under Transverse Cyclic Load711(2004); http://dx.doi.org/10.1063/1.1774551View Description Hide Description
A cryogenic cable press has been built and recently modified to investigate the life time properties and changes in the mechanical and electrical properties of full‐size ITER (International Thermonuclear Experimental Reactor) conductors. The press is a fully automatically controlled operating system designed to test Cable‐In‐Conduit Conductors (CICC) under transverse variable load along 40,000 cycles at temperatures from 4.2 to 300 K. The designed lifetime of the press, with moving parts and minimized friction at cryogenic temperatures, is at least a few millions of cycles. The maximum press load is 320 kN with a stroke of 5.5 mm. The maximum sample length amounts to 400 mm. The force on the cable and the compression are monitored simultaneously in order to determine the mechanical cable deformation properties and losses. A superconducting dipole coil integrated in the press surrounding the sample, provides the DC and AC magnetic field required to perform magnetization measurements with pick‐up coils. In addition, interstrand resistance (R c) measurements are carried out. To date, more than ten full‐size CICC samples have been tested, each subjected to 40,000 cycles. All samples show changes in R c, coupling loss and mechanical properties with cycling, some of them are quite significant, depending on the specific conductor properties. Some typical design features of the press are presented and discussed.
711(2004); http://dx.doi.org/10.1063/1.1774552View Description Hide Description
High strength conductors, used for the construction of pulsed magnets at NHMFL, must withstand demanding stress, strain and cyclic fatigue requirements. The safe design and operation of pulse magnets requires an understanding of the expected conductor performance as determined from design‐specific low‐cycle fatigue tests. A test fixture has been developed to perform fatigue stress cycling at 77 K that enables the application of axial tension and compression in a stress or strain control mode. Special wedge grips with low thermal mass were designed that are capable of reverse cycling (tension‐compression) of various size specimens. The low cycle fatigue life of Glidcop‐AL60™, a commercially available high strength/high conductivity conductor, has been characterized and is reported. Stress and strain data acquired for the tests, are evaluated to assess the material’s strain hardening or strain softening characteristics and its influence on fatigue life. The influence of test control mode (stress control versus strain control), and r‐ratio on the fatigue life, are discussed.
711(2004); http://dx.doi.org/10.1063/1.1774553View Description Hide Description
Nb 3Sn strands being developed for future HEP applications have about four times the critical current at 4.2 K, 12 T, and significantly larger effective filament diameters than ITER‐class strands, upon which the present short‐sample testing protocol is based. Because of shortcomings in stability when testing these HEP strands with the ITER barrel, we have designed and built a new, low‐cost Nb 3Sn short sample test fixture that provides excellent stability and allows for higher throughput at lower cost than the ITER design. The new design uses stainless steel as the central region of the barrel, but it can also incorporate Ti‐6A‐14V to produce different strain states on the strand upon cooldown. Soldering the modern Nb 3Sn strand to the stainless steel barrel provided the best stability in experiments, where current‐voltage transitions were recorded up to 150 μV and up to ∼ 1000 A. Current‐voltage data were also obtained at fields as low as 8.5 T for state‐of‐the‐art HEP strands. A continuous round groove was a key design feature because it ensures a smooth transition between the region where current transfers into the strand and where it is measured. This groove also makes it possible to transfer samples onto the barrel after the heat treatment without damage. We discuss the implications of our barrel design and testing experiences for present testing difficulties and protocols.
711(2004); http://dx.doi.org/10.1063/1.1774554View Description Hide Description
The knowledge of accurate performance data of porous materials is an essential need for investigation of new candidate sorbent materials for use in cryosorption devices. The temperature range between 5 K and 20 K is foreseen to be used in order to exploit the cryosorption mechanism in cryovacuum pump systems for nuclear fusion. But direct experimental data at cryogenic temperatures are very scarce in the open literature, especially at temperature levels other than LHe or LN.
Thus, a novel device was developed to measure sorption characteristics of porous materials under variable temperature cryogenic conditions (3.5 K to 100 K). The COOLSORP facility is based on a commercially available pore‐analyser, upgraded by a heatable, closed He cycle, two‐stage Gifford McMahon refrigerator. This facility is characterised by its wide range of accessible pressures, from ambient down to 10−4 Pa.
The paper describes the facility set‐up and and presents typical examples of low temperature sorption data on different gases (helium, hydrogen, deuterium, nitrogen) for activated carbon and getter materials. COOLSORP is demonstrated to be a versatile facility which cannot only be used for scientific purposes to investigate different materials, but also for quality assurance purposes.
711(2004); http://dx.doi.org/10.1063/1.1774555View Description Hide Description
When performed in conjunction with neutron diffraction, in situ loading offers unique insights on microstructural deformation mechanisms. This is by virtue of the penetration and phase sensitivity of neutrons. At Los Alamos National Laboratory room and high temperature (up to 1500°C) polycrystalline constitutive response is modeled using finite element and self‐consistent models. The models are compared to neutron diffraction measurements. In doing so the implications of slip and creep to microstructural response have been explored. Recently we have been considering low temperature phenomena. This includes changes in deformation mechanisms such as the increased predilection for twinning over slip. Since this is associated with measurable texture changes as well as microstructural strain effects, it is well suited for study using neutron diffraction. This paper outlines the design and rationale for a cryogenic loading capability that will be used on the Spectrometer for MAterials Research at Temperature and Stress (SMARTS) at the Los Alamos Neutron Science Center (LANSCE).
Phase Stability of the Fe‐Cr‐Mn System and the Problem of Development of Stainless Steels on its Basis711(2004); http://dx.doi.org/10.1063/1.1774556View Description Hide Description
The Fe‐Cr‐Mn system with 2 – 15 % Cr and 20 – 50 % Mn, ⩽ 0.03 % C, ⩽ 0.05 % N was investigated after quenching from 1273 K and after quenching and subsequent one‐hour tempering at 973 K.
Phase diagrams are plotted for the Fe‐Cr‐Mn alloys after cooling and deformation at 20 K. Also, the diagrams of their mechanical properties are constructed.
A closed, earlier unknown region of concentrations has been revealed, where the alloys have extraordinarily high plasticity and impact strength at 20 K exceeding the corresponding room temperature values. The analysis of the diagrams shows that the high plasticity is due both to the martensitic transformation and to the pre‐martensite state. To improve the anticorrosive effect in cryogenic and special engineering applications, it is reasonable to use alloys containing Cr up to 14 % and Mn up to 24 – 30 %. Such alloys have quite high plasticity and strength.
Microstructural Stability of 316 Stainless Steel During Long Term Exposure to High Magnetic Fields at Cryogenic Temperatures711(2004); http://dx.doi.org/10.1063/1.1774557View Description Hide Description
The effect of long term exposure to high magnetic fields at cryogenic temperatures on the microstructural stability of austenitic stainless steel was investigated. Three samples of SUS316 were prepared. One was as‐machined, the second was solution heat‐treated, and the last was solution heat‐treated followed by a sensitization heat treatment. The samples were attached to the helical coil cover of the Large Helical Device, which is a large plasma experimental device operating with a superconducting magnet system. The maximum magnetic field the samples experienced was about 2.56 T for over 100 cycles during which time the temperature was kept at about 4.5 K for approximately 300 days. Before and after the exposure, the susceptibility was measured by a superconducting quantum interference device and it was confirmed that the austenitic phase was stable and did not produce any additional martensite by the long term exposure to the high magnetic fields at cryogenic temperatures.
711(2004); http://dx.doi.org/10.1063/1.1774558View Description Hide Description
To evaluate material risk caused by human‐error, the notch effects on the fatigue properties of forged Ti‐5A1‐2.5Sn ELI alloy have been investigated at cryogenic temperatures. Smooth and notched specimens with the Kt =1.5, 2 and 3 were prepared. High‐cycle fatigue tests were carried out at 4, 77 and 293 K. The S‐N curves of each specimen shifted to higher stress level with a decrease of the test temperature. At 4 K, the fatigue strength of the Kt =3 specimens were substantially lower than those of the smooth specimens. Although the notch effects on the fatigue properties of the Kt =1.5 and the Kt =2 notched specimens are not clear or significant. Fatigue crack initiation sites of the smooth and the Kt =1.5 notched specimens were in the specimen interior (internal type fracture) and those of the Kt =2 and the Kt =3 notched specimens were at the notch root (surface type fracture). The location of the fatigue crack initiation sites showed transition from the internal type fracture for the Kt =1.5 notched specimens to the surface type fracture for the Kt =2 notched specimens. Therefore, the Kt values of the internal fatigue crack initiation sites correspond between 1.5 and 2. The sizes of the internal fatigue crack initiation sites were calculated by the . The sizes of the Kt =1.5 notched specimens and the smooth specimens were in a similar range and the fatigue strength of the two are not significant.
711(2004); http://dx.doi.org/10.1063/1.1774559View Description Hide Description
For the last few decades, the E. O. Paton Electric Welding Institute has been active in the field of cryogenic materials science. Integrated research on development of new grades of steels and alloys for cryogenic engineering was carried out in collaboration with the leading institutions of Russia, Ukraine, and Georgia. Commercially applied welding technologies and consumables were developed. They include large, spherical tanks for storage of liquefied gases (from oxygen to helium) under high pressures; space simulators with a capacity of 10 000 m3 and more; and load‐carrying elements of superconducting fusion magnetic systems for the TOKAMAK, MGD, and ITER series.
Data Sheet Program and Mechanical Properties of Ti‐5Al‐2.5Sn ELI and Alloy 718 at Cryogenic Temperatures711(2004); http://dx.doi.org/10.1063/1.1774560View Description Hide Description
In the development of Japan’s self‐developed H‐IIA launch vehicle, it is important to sufficiently comprehend the properties of materials under conditions in which the materials are used in the system for its design and the improvement of its reliability. Through the process of failure analysis of the LE‐7 engine of H‐II No. 8 in 1999, detailed materials data and photographs of the fracture surface were required as reference data to determine in terms of fracture morphology and to analyze the fracture stress. A series of mechanical properties tests, such as tensile tests, impact tests, fracture toughness tests, and fatigue tests, on Ti‐5Al‐2.5Sn ELI and Alloy 718 at room temperature to 4K were mainly conducted by NIMS and NASDA. The obtained tensile and fracture toughness properties were a little bit smaller than those reported by NASA and NRIM, however, the fatigue properties were relatively lower than the data reported so far. Data resulting from the tests were reviewed in detail and published in the form of data sheets. This paper will introduce the data sheet program on space use materials and discuss an effect of microstructure of Ti‐5Al‐2.5Sn ELI and Alloy 718 on their mechanical properties at cryogenic temperatures.
Effects of Co and Al Contents on Cryogenic Mechanical Properties and Hydrogen Embrittlement for Austenitic Alloys711(2004); http://dx.doi.org/10.1063/1.1774561View Description Hide Description
The effects of Co and Al content on ambient and cryogenic mechanical properties, microstructure and hydrogen embrittlement of a high strength precipitate‐strengthened austenitic alloy (Fe‐Ni‐Cr‐Mo system) had been investigated with temperature range from 293K to 77 K. Hydrogen embrittlement tests were conducted using the method of high pressure thermal hydrogen charging. It was found that increasing Co content can cause increasing in ambient and cryogenic ductility, but has less effect on ultimate tensile strength. When Co content is 9.8%, obvious decrease was found in cryogenic yield strength. Increasing Al content can result in decreasing ambient and cryogenic ductility and severe hydrogen embrittlement, but slight increase in cryogenic yield strength. Increasing Co content, reducing Al content, and decreasing test temperature tend to decrease the hydrogen embrittlement tendency for the alloys. This work showed that the alloy with composition of Fe‐31%Ni‐15%Cr‐5%Co‐4.5%Mo‐2.4%Ti‐0.3%Al‐0.3%Nb‐0.2%V has the superior cryogenic mechanical properties and lower hydrogen embrittlement tendency, is a good high strength cryogenic hydrogen‐resistant material.
711(2004); http://dx.doi.org/10.1063/1.1774562View Description Hide Description
Tensile tests of type 304L and 316L steels were carried out using round bar specimens with a notch in liquid helium, hydrogen, liquid nitrogen and at ambient temperature. The obtained tensile strengths were compared with the tensile strengths of smooth specimens. For smooth specimens, tensile strength increased with a decrease in temperature and the strengths in liquid helium and hydrogen show similar values in both steels. For notched specimen of 304L steel, tensile strength (including fracture strength) increased noticeably from ambient to liquid nitrogen temperature but showed a large decrease in liquid helium and hydrogen. In liquid hydrogen and helium, the tensile strength is a little lower in liquid hydrogen than in liquid helium and both strengths are lower than tensile strengths of smooth specimens. For notched specimen of 316L steel, an increase in tensile strength from ambient to liquid nitrogen temperature was not so large and a decrease from liquid nitrogen to liquid hydrogen was small. The tensile strengths in liquid helium and hydrogen were nearly same and higher than those of smooth specimens. Different behavior of serration was observed between liquid helium and hydrogen, and between 304L and 316L steels. The reasons for these differences were discussed using computer simulation.
Characterization of Alloys with Potential for Application in Cable‐in‐Conduit Conductors for High‐Field Superconducting Magnets711(2004); http://dx.doi.org/10.1063/1.1774563View Description Hide Description
Since the introduction of the cable‐in‐conduit conductor (CICC) concept, a variety of alloys have been proposed for fabricating the jacket. The jacket provides primary containment of the supercritical helium coolant and is typically also the primary structural component for the magnet. These functions create requirements for strength, toughness, weldability, and fabricability in tubular form. When the CICC uses Nb 3Sn, there are additional requirements to accommodate the manufacturing and heat‐treatment processes for the superconductor as well as its strain‐sensitive performance during operation. Both of the present favorite jacket alloys, Incoloy 908 and modified (ultra‐low carbon) 316LN, have both demonstrated acceptable functionality as well as a few undesirable features. In this paper, we present data from cryogenic mechanical tests on a group of heat‐resistant, high‐strength superalloys that appear to offer equal or better mechanical performance (e.g. strength, toughness, and modulus) while mitigating the undesirable aspects (e.g. SAGBO in the case of I908 and thermal‐expansion mismatch with Nb 3Sn in the case of 316LN). Data are presented for each alloy in the as‐received and aged conditions. These alloys are presently being considered as candidates for use in the next‐generation hybrid magnet for the NHMFL but may also be of interest to the fusion and energy storage communities.
Thermal Contraction Measurements of Various Materials Using High Resolution Extensometers between 290 K and 7 K711(2004); http://dx.doi.org/10.1063/1.1774564View Description Hide Description
Thermal contraction measurements are carried out between 290 K and 7 K using a 50 mm gauge length double extensometer system. This new technique is developed as an in situ working thermal expansion testing unit placed inside a variable temperature cryostat having the accuracy of better than +/− 15 μm/m. The resolution of the extensometers based on strain gauge technology is below 0.1 μm. Using these extensometers the displacement of the materials are measured overnight during the warm up period of the cryostat. These measurements use the reference curve of the material Zerodur®, an ultra low thermal expansion glass ceramic commercial product. The reference curve consists of the cool down and warm up displacement behavior of the extensometers. The advantage of this system is that it allows measuring of ∼ 60 mm long samples with thickness between 0.2 mm and 20 mm. In toto, several structural materials used by ITER superconducting coils are measured with respect to their thermal expansion behavior. Within this context also a set of fully austenitic nitrogen alloyed stainless steels with Mn contents up to 40 % are characterized with respect to their thermal expansion. In addition, superconducting Nb 3Sn wires, high Tc tapes of Type Bi‐2223, and Si/Ge single crystals are also directly measured using this methodology.