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Structural alloys for high field superconducting magnets

Description: Research toward structural alloys for use in high field superconducting magnets is international in scope, and has three principal objectives: the selection or development of suitable structural alloys for the magnet support structure, the identification of mechanical phenomena and failure modes that may influence service behavior, and the design of suitable testing procedures to provide engineering design data. This paper reviews recent progress toward the first two of these objectives. The structural alloy needs depend on the magnet design and superconductor type and differ between magnets that use monolithic and those that employ force-cooled or ICCS conductors. In the former case the central requirement is for high strength, high toughness, weldable alloys that are used in thick sections for the magnet case. In the latter case the need is for high strength, high toughness alloys that are used in thin welded sections for the conductor conduit. There is productive current research on both alloy types. The service behavior of these alloys is influenced by mechanical phenomena that are peculiar to the magnet environment, including cryogenic fatigue, magnetic effects, and cryogenic creep. The design of appropriate mechanical tests is complicated by the need for testing at 4/sup 0/K and by rate effects associated with adiabatic heating during the tests. 46 refs.
Date: August 1, 1985
Creator: Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Role of dislocation theory in the design of engineering materials

Description: The science of materials development has progressed to a stage in which it is possible to compose a recipe for new materials. The recipe has three steps: given a desirable set of properties and material constraints, one identifies a composition and microstructure to achieve them; given a desirable composition and microstructure, one identifies a processing sequence to achieve them; given a trial alloy, one conducts analytical testing to identify its shortcomings and overcomes them. In effecting each stage of this recipe, it is usually necessary to be aware of and understand the role of the dislocations which determine material properties, define material microstructure, and control its evolution. The role of dislocations is discussed. The text contains examples of particular alloy development efforts, and suggestions for research in dislocation theory which might contribute to the solution of significant problems in materials development.
Date: June 1, 1980
Creator: Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Moessbauer study of microstructural and chemical changes in Fe-9Ni steel during two-phase tempering

Description: Two-phase tempering of martensitic Fe-9Ni steel serves to enhance the low temperature toughness and forms austenite precipitates in this material. Hyperfine field effects in Fe-Ni alloys were systematized so that tempering induced chemical composition changes in the martensite could be quantified by Moessbauer spectrometry. The kinetics of segregation of alloy elements from the martensite into the fresh austenite can be determined simultaneously with the amount of austenite which was formed.
Date: November 1, 1980
Creator: Fultz, B. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Influence of processing on the cryogenic mechanical properties of high strength high manganese stainless steel

Description: New high strength structural steels have been required for the large superconducting magnets that will be used for the next step test facility for fusion reactor research. The new materials must have high yield strength accompanied with better toughness and better fatigue resistance compared with the conventional nitrogen-strengthened stainless steels such as AISI 304LN and 316LN that were used for the cases of the toroidal field coils for the Large Coil Project. A number of new high manganese austenitic steels have been proposed for new cryogenic structural alloys since they can offer low cost, stable austenite and high strength.
Date: August 1, 1983
Creator: Ogawa, R. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Improvements in the weldability of a superconductor sheath material

Description: This paper investigates the effects of chemistry and heat treatment variation on the 4-K tensile properties of A-286, a candidate sheath material for force-cooled superconductors. Currently, full use of A-286 and similar superalloys is limited by the observed low yield and ultimate tensile strengths in the welded and aged condition. The low strength is shown to be associated with the formation of precipitate-free zones as a result of alloying-element segregation during weld pool solidification. It has been determined that minor modifications of the weld-metal chemistry by the addition of Ti reduce precipitate-free-zone formation, resulting in matching weld-metal and base-plate strengths at 4 K. Furthermore, nucleation of the ..gamma..' hardening phase has been found to be a strong function of temperature and composition. Modified heat-treatment schedules have been determined that are amenable to superconductor fabrication and that resulted in increased weld hardening and improved 4-K tensile properties.
Date: August 7, 1985
Creator: Summers, L.T. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Ductile superconducting wire through novel metallurgical techniques

Description: Ductile superconducting wires can be formed through controlled precipitation of the A15 phase from supersaturated solution in the solid state. The current research has focused on melting, homogenizing, and thermomechanically processing supersaturated solutions of Ga in V. A diagram of the rolling process is given. (SDF)
Date: January 1, 1978
Creator: Hong, M. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Cryogenic mechanical properties of high-manganese steel weldments

Description: The structural alloys used in fusion reactor magnets of the next generation are required to have a 4.2 K yield strength and fracture toughness combination superior to that of alloys used currently. An alloy of nominal composition 18Mn-5Ni-16Cr-0.22N after proper thermomechanical treatment approaches the JAERI projected requirements and exceeds the proposed US requirements for 4.2 K yield strength and fracture toughness in the base metal. However, the properties in the welded condition are still uncertain. This work investigates the effect of autogenous GTAW on the cryogenic properties of this alloy. It was found that the 4.2 K yield strength of the weld can be increased through the addition of nitrogen to a 75% He/25% Ar shield gas; specifically, a yield strength comparable to that of the base metal was achieved for a 6 vol % nitrogen addition. Fracture toughness data are still preliminary; however, autogenous welds made on this alloy approach the US requirements for both yield strength and K/sub Ic/.
Date: August 1, 1985
Creator: Chan, J.W. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Strength vs toughness relation in Fe-high manganese alloys

Description: Charpy impact tests were performed on the 16 to 36 wt % Mn steels whose tensile properties have already been reported. The effect of Mn content on the ductile-brittle transition behavior was basically identical with other workers' results. However, since the reasons for these phenomena are quite unclear, advanced experimental facts are discussed.
Date: April 1, 1984
Creator: Tomota, Y. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Three-dimensional analysis of cellular microstructures by computer simulation

Description: For microstructures of the ''cellular'' type (isotropic growth from a distribution of nuclei which form simultaneously), it is possible to construct an efficient code which will completely analyze the microstructure in three dimensions. Such a computer code for creating and storing the connected graph was constructed. (DLC)
Date: June 1, 1977
Creator: Hanson, K. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Influence of alloy composition on the cryogenic mechanical properties of AISI 200 grade high-manganese austenitic steels

Description: Research on the effect of composition on the cryogenic mechanical properties of high-Mn austenitic steels showed that both the yield strength and change of strength with alloy processing increased significantly with increasing interstitial content. Alloy toughness deteriorated if carbon content was raised to 0.1% or higher or if delta-ferrite was retained in the as-cooled alloy. On the basis of these investigations an alloy of nominal composition 18Mn-5Ni-16Cr-0.024C-0.22 N was made and tested at 4K. Both its strength-toughness characteristic and fatigue crack growth properties compared favorably to those of 304LN and 304N cryogenic steels.
Date: May 1, 1982
Creator: Ogawa, R. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Research toward new alloys for generator retaining rings

Description: The research reported here was undertaken to develop an alloy suitable for use in the retaining rings of two-pole electrical generators that would have three key properties: a yield strength of 200 ksi or greater with good residual toughness; resistance to hydrogen embrittlement and stress-corrosion cracking; and processability through heat treatment after hot forming, to avoid the necessity of cold forming of the ring. The principal alloy developed during the course of this work was an iron-based superalloy, designated EPRI-T, which has nominal composition Fe-34.5Ni-5Cr-3Ti-3Ta-0.5A1-1.0Mo-0.3V-0.01B. The alloy is an iron-based superalloy which is strengthened through the formation of cubic ..gamma..' precipitates of composition Ni/sub 3/(Ti,Ta,Al). When given appropriate aging treatment from the as-forged condition the alloy achieves yield strength in excess of 200 ksi with good residual toughness and promising resistance to cracking in gaseous hydrogen and salt water. The composition and processing of the alloy are the result of sequential metallurgical development, the steps of which are described. The alloy was chosen from a class of iron-based superalloys to achieve high strength in thick sections while maintaining reasonable costs, melting practice, and hot formability. The nickel content of the alloy was adjusted to insure that the alloy would be paramagnetic austenite after aging reaction to form the Ni/sub 3/X strengthening precipitates. Tantalum was included among the ..gamma..'-forming elements to increase the lattice mismatch of the precipitate and improve alloy strength. Chromium was added to the composition to stabilize the austenite phase and eliminate stress-corrosion cracking susceptibility due to martensitic transformation of the austenite. The Mo-V-B group was included to inhibit intergranular precipitation of the equilibrium eta phase and hence suppress a tendency toward intergranular fracture in the alloy.
Date: November 1, 1981
Creator: Morris, J.W. Jr. & Chang, K.M.
Partner: UNT Libraries Government Documents Department

Statistical Analysis of SNAP 10A Thermoelectric Converter Element Process Development Variables

Description: Statistical analysis, primarily analysis of variance, was applied to evaluate several factors involved in the development of suitable fabrication and processing techniques for the production of lead telluride thermoelectric elements for the SNAP 10A energy conversion system. The analysis methods are described as to their application for determining the effects of various processing steps, estabIishing the value of individual operations, and evaluating the significance of test results. The elimination of unnecessary or detrimental processing steps was accomplished and the number of required tests was substantially reduced by application of these statistical methods to the SNAP 10A production development effort. (auth)
Date: December 15, 1962
Creator: Fitch, S. H. & Morris, J. W.
Partner: UNT Libraries Government Documents Department

Thermomechanical processing of a two-phase Al-Cu-Li-Zr alloy

Description: The effect of large second-phase particles on the workability, mechanical properties, and response to thermochemical processing of an Al-2.49Cu-2.37Li-0.13Zr alloy was investigated. The solution-treated alloy was compared with a dispersoid-containing alloy fabricated by aging the base alloy at an intermediate temperature to bring out second-phase particles. Extensive deformation and short heat treatments that cause some of the solute to be incorporated into dispersoid particles were both found to be beneficial to the mechanical properties of the alloy. In specimens which failed intergranularly, the presence of dispersoid particles did not significantly affect the fracture properties.
Date: June 1, 1985
Creator: Glazer, J. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

The use of microstructure control to toughen ferritic steels for cryogenic use. II. Fe--Mn steels

Description: The research reported here addresses the microstructural modification of ferritic Fe-Mn alloys to improve low temperature properties. The alloys Fe-12Mn-0.2Ti and Fe-8Mn-0.2Ti were specifically studied. In the as-quenched condition the alloys have ductile-brittle transition temperatures near -50/sup 0/C and room temperature respectively. The brittleness of Fe-12Mn is due to the intrusion of an intergranular fracture mode; that of Fe-8Mn is due to quasi-cleavage. The transition temperature of the 12Mn alloy may be suppressed by annealing in the two-phase (..cap alpha.. + ..gamma..) range to introduce a distribution of austenite or by grain refinement through deformation processing. In the latter case an excellent combination of strength and toughness is obtained at liquid nitrogen temperature. The 12Mn alloy may not be thermally processed to fine grain size because of the malevolent influence of the epsilon-martensite phase present in the as-quenched structure. No such phase is present in the 8Mn alloy. This alloy may be thermally processed to ultrafine grain size with a concommitant marked improvement in low temperature mechanical properties.
Date: December 1, 1976
Creator: Hwang, S. K. & Morris, J. W. Jr.
Partner: UNT Libraries Government Documents Department

Development of a high strength, hydrogen-resistant austenitic alloy. [Fe-36 Ni-3 Ti-3 Ta-1. 3 Mo]

Description: Research toward high-strength, high toughness nonmagnetic steels for use in the retaining rings of large electrical generators led to the development of a Ta-modified iron-based superalloy (Fe-36 Ni-3 Ti-3 Ta-0.5 Al-1.3 Mo-0.3 V-0.01 B) which combines high strength with good toughness after suitable aging. The alloy did, however, show some degradation in fatigue resistance in gaseous hydrogen. This sensitivity was associated with a deformation-induced martensitic transformation near the fracture surface. The addition of a small amount of chromium to the alloy suppressed the martensite transformation and led to a marked improvement in hydrogen resistance.
Date: August 1, 1980
Creator: Chang, K.M.; Klahn, D.H. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Advances in the heat treatment of steels

Description: A number of important recent advances in the processing of steels have resulted from the sophisticated uses of heat treatment to tailor the microstructure of the steels so that desirable properties are established. These new heat treatments often involve the tempering or annealing of the steel to accompish a partial or complete reversion from martensite to austenite. The influence of these reversion heat treatments on the product microstructure and its properties may be systematically discussed in terms of the heat treating temperature in relation to the phase diagram. From this perspective, four characteristic heat treatments are defined: (1) normal tempering, (2) inter-critical tempering, (3) intercritical annealing, and (4) austenite reversion. The reactions occurring during each of these treatments are described and the nature and properties of typical product microstructures discussed, with specific reference to new commercial or laboratory steels having useful and exceptional properties.
Date: June 1, 1978
Creator: Morris, J.W. Jr.; Kim, J.I. & Syn, C.K.
Partner: UNT Libraries Government Documents Department

Computer simulation of the martensite transformation in a model two-dimensional body

Description: An analytical model of a martensitic transformation in an idealized body is constructed and used to carry out a computer simulation of the transformation in a pseudo-two-dimensional crystal. The reaction is assumed to proceed through the sequential transformation of elementary volumes (elementary martensitic particles, EMP) via the Bain strain. The elastic interaction between these volumes is computed and the transformation path chosen so as to minimize the total free energy. The model transformation shows interesting qualitative correspondencies with the known features of martensitic transformations in typical solids.
Date: June 1, 1979
Creator: Chen, S.; Khachaturyan, A.G. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Computer simulation of the martensite transformation in a model two-dimensional body

Description: An analytical model of a martensitic transformation in an idealized body is constructed and used to carry out a computer simulation of the transformation in a pseudo-two-dimensional crystal. The reaction is assumed to proceed through the sequential transformation of elementary volumes (elementary martensitic particles, EMP) via the Bain strain. The elastic interaction between these volumes is computed and the transformation path chosen so as to minimize the total free energy. The model transformation shows interesting qualitative correspondencies with the known features of martensitic transformations in typical solids.
Date: May 1, 1979
Creator: Chen, S.; Khachaturyan, A.G. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Computer simulation of the formation of tweed and modulated structures in decomposition reactions

Description: A model of coarsening in a heterogeneous cubic alloy with cubic or tetragonal precipitates is proposed. According to the model the coarsening is controlled by the relaxation of the elastic strain energy. The computer simulation of coarsening demonstrates good agreement with electron microscopic observation of the structure and diffraction pattern.
Date: March 1, 1979
Creator: Chen, S.; Morris, J.W. Jr. & Khachaturyan, A.G.
Partner: UNT Libraries Government Documents Department

Cryogenic structural materials for superconducting magnets

Description: This paper reviews research in the United States and Japan on structural materials for high-field superconducting magnets. Superconducting magnets are used for magnetic fusion energy devices and for accelerators that are used in particle-physics research. The cryogenic structural materials that we review are used for magnet cases and support structures. We expect increased materials requirements in the future.
Date: February 22, 1985
Creator: Dalder, E.N.C. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department