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From time to time in the paternity laboratory evidence for non-paternity is obtained in one or more genetic systems, while the remaining systems strongly suggest paternity. While this can occur by chance, such cases should be pursued further. Such a situation can be an important clue that silent alleles are present, if the evidence for non-paternity is limited to conditions of apparent opposite homozygousity (so-called “second order exclusions”). Rarely, such a situation can be a clue that the evidence for non-paternity is based on serologic irregularities; confirmation may be prudent. More commonly, especially when the evidence for non-paternity is incontrovertable, the situation provides a clue that a man related to the tested man is the father. We derive the theoretical framework for such an evaluation and review our experience with case material, which demonstrates that undisclosed unclehood is by no means rare.

Previous research in this laboratory led to the development of thermal cycling techniques that establish an extremely fine effective grain size in 12Ni1–4 and 9Ni4, 5 cryogenic steels. In the grain-refined condition these alloys offer a good combination of strength and toughness at 4 K and have possible applications in the structures of cryogenic devices such as high field superconducting magnets. But the structures of these devices are usually welded, and candidate structural alloys must, hence, retain good properties in the welded condition. To weld the grain-refined steels one must overcome the dual problems of brittleness in the weld deposit and brittleness due to grain coarsening in the heat-affected zone (HAZ).

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.

The effect of microstructural changes on the ductile-brittle transition temperature (DBTT) was studied in a titanium-getter ed Fe-8Ni-2 Mn-0.15 Ti alloy. A fairly strong grain size dependence of the transition temperature, 8°C/mm−1/2, was found. Grain size refinement from 38 μm (ASTM #6.5) to 1.5 μm (ASTM #15.5) through a four-step thermal treatment lowered the transition temperature by 162°C. A small amount of retained austenite was introduced into this grain-refined microstructure, and the transition temperature was reduced by an additional 120 ~ 150°C. The reduction of the DBTT due to retained austenite was smaller when the austenite was in a large-grained structure (64°C). The distribution and stability of retained austenite were also studied.

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 K and by rate effects associated with adiabatic heating during the tests.

This paper reviews the linear elastic theory of the defect solid solution. It is tutorial in nature, and is primarily intended to outline the development of the theory into the mathematical form that is most suitable for the solution of practical problems. The theory treats solid solutions containing distributions of solute defects that distort the solvent lattice and interact elastically with one another. It determines the total strain of the solvent lattice and the elastic contribution to the free energy of the solution in the strong harmonic approximation. The theory is specifically developed for a binary solution of point defects in the absence of external stress. It can be extended to treat multicomponent solutions, stressed solutions, and solutions of finite defects or macroscopic inclusions; the equations governing these complex systems are also presented. The model is finally used to consider ordering and decomposition reactions in solutions whose components interact elastically.

Magneto-mechanical effects, or effects of magnetic fields on mechanical properties of materials, are reported for two steels containing austenite that undergoes an fcc→bcc martensitic transformation during plastic deformation. Stress-strain curves from tensile tests of AISI 304 stainless steels and 9Ni steels were measured in magnetic fields as large as 18 T at temperatures of 4 K, 77 K and room temperature. Even in 18 T magnetic fields at cryogenic temperatures the magneto-mechanical effects were small, but they were reproducible and scaled with the strength of the magnetic field and the amount of transformation. Magneto-mechanical effects in steels with metastable austenite provide a unique means of determining how martensitic transformations affect mechanical behavior. The fcc→bcc transformation makes an important contribution to the work hardening of both AISI 304 and 9Ni steel, so the more rapid transformation during magnetic exposure results in a higher strength and a reduced elongation of tensile specimens. In AISI 304 stainless steel a reduced flow stress in the magnetic field was found at small plastic strains.

The superconducting compounds that show greatest promise for the windings of high-field superconducting magnets are intermetallic compounds of stoichiometric composition A3B in the A15 crystal structure. This class of compounds includes the superconducting phases Nb3Sn, V3Ga, Nb3A1, Nb3Ge, and others. They combine high critical temperature (Tc) with high upper critical field (Hc2) and high critical current density (Jc). These compounds are, however, brittle intermetallic phases. They are therefore difficult to form into long lengths of superconducting wires for use in high-field magnet windings.

This paper is intended to describe and illustrate the use of phase transformations in the design of new alloy steels. The general method of alloy design is described. Two examples are discussed: the development of new ferritic structural steels for use at cryogenic temperature, and the development of ‘dual phase’ steels for automotive use.

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 superailoys 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 γ’ 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.

Prior work on internal tin wire has shown that an increase in critical current results when the Nb3Sn reaction temperatures (650–730°C) are preceded by low temperature diffusion heat treatments that distribute the tin. These heat treatments produce a more uniform tin distribution through the niobium filament array before substantial Nb3Sn formation has occurred. Heat treatments as long as 19 days have been proposed as the optimal heat treatment for the conductor. However, it is possible to substantially reduce the low temperature heat treatment time while retaining the same high critical current. The success of shortened heat treatments may be interpreted on the basis of the Cu-Sn reaction, diffusion kinetics and the Nb3Sn growth kinetics.

The microstructure and mechanical properties of Pb-Sn solder joining Cu plates were studied. Yticrostructural observations were made on both the bulk Pb-Sn solder and on the interface between the solder and Cu plates. Pb-Sn solder has a two-phase microstructure in which the Pb-rich phase is the weaker. β-Sn precipitates in the Pb-rich phase were characterized in TEM. Intermetallic phases (Cu6Sn5and Cu3Sn) that form during the reaction of molten Pb-Sn solder with Cu were investigated. Solder joints were tested to fracture in both shear and tensile configurations. The mechanical properties and fracture surface characteristics are reported.

We present a development and discussion of the biostatistical evaluation of deoxyribonucleic acid (DNA) probe evidence in forensic science cases of disputed paternity and identity. We restrict ourselves to single-locus codominant systems (highly analogous to more conventional systems) which have the apparently novel complication of an experimentally continuous allele frequency distribution. This complication necessitates reformulations of standard biostatistical summaries of the evidence (the paternity index (PI) and the phenotype frequency, respectively). These reformulations, rather than representing a unique case, have applicability to the evaluation of evidence obtained in standard genetic systems now in widespread use.

Critical current density as a function of applied field, Jc(H), is the key design criterion for many applications of superconducting wire. Some correlations between microstructure and good properties have been made on the basis of both theory and experimentµ however, these relationships are not yet well enough defined to obviate the need to test actual samples frequently during the research and design process. The availability of accurate and reliable testing facilities is therefore critical to the development of practical superconductors.

AISI 304 stainless steels are the most widely used structural alloys in cryogenic service. To the cryogenic engineer they offer good fracture toughness, good fatigue properties, and adequate strength at 4 K. Additionally, their paramagnetism and corrosion resistance are often desirable properties. Recently 304 stainless steels have been used in superconducting magnet structures for magnetic fusion energy devices. Large amounts of steel are required in these structures, for example nearly 300 tonnes of AISI 304LN were used in the yin-yang magnet cases for the Mirror Fusion Test Facility at the Lawrence Livermore National Laboratory.

In recent years, there have been a number of investigations [1–6] on the cryogenic mechanical properties of Fe—Mn alloys. Such studies showed that martensitic Fe—Mn alloys (6 to 12 wt.% Mn) have excellent cryogenic strength. The cryogenic toughness is poor, however; the alloys exhibit the characteristic ductile-brittle transition near room temperature.

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.

Most existing or planned high field superconducting magnets use austenitic stainless steels for the magnet structure because these materials are available, paramagnetic, and tough at 4K. Many common austenitic (γ-phase) stainless steels are, however, structurally metastable at 4K. They prefer the bcc (α-phase),and will undergo spontaneous martensite transformations under appropriate conditions. Metastable austenite also appears in other classes of cryogenic structural steel. Some of the promising new high-Mn steels are metastable with respect to the indirect transformation γ→e→α ,where e-martensite is a hexagonal phase. Ferritic steels are commonly toughened for low temperature service by the precipitation of metastable austenite within the ferritic matrix. The martensite transformation is promoted both by high magnetic fields [1] and mechanical loads [2] in ways which are imperfectly understood, but which may affect structural performance or reliability in the high stress, high field regions of the large and powerful superconducting magnets now being developed. This paper briefly reviews the combined effects of magnetic fields and mechanical loading on this transformation, reports two initial experiments with a pulsed magnetic field, and describes a new testing facility which has been established to measure cryogenic mechanical properties in steady 8T magnetic fields.

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 accomplish 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) intercritical 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.

The steels commonly specified for structural applications at LNG and lower temperatures, 9% Ni steel, austenitic stainless steels, and Invar alloys, all have a relatively high nickel content. While the nickel addition contributes significantly to good low-temperature properties of these alloys, it also adds substantially to the cost. Consequently, there is incentive to develop techniques for reducing or eliminating the nickel content of cryogenic steels while retaining good cryogenic properties. Steels containing 5 to 6% nickel were recently introduced in the United States [1] and in Japan [2] in response to this need. Further decreases in the nickel content would be desirable.

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 U.S. 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 U.S. requirements for both yield strength and KIc.

The asymptotic form of the two-body interatomic potentials arising from pseudopotential theory, V(r) = V 0 cos ( 2k F r) (2k F r ) 3 , is used to discuss the relative cohesive energies of simple metallic structures. Use of this potential allows the thermodynamically preferred structure of a simple metallic element or solid solution at 0K to be determined as a function of valence only. The appropriate lattice sums are performed exactly for the f.c.c., h.c.p. (with ideal axial ratio) and b.c.c. structures. In addition, the approximate interplanar interaction of Blandin et al. is summed for polytypic structures. Two modifications of the potential are also considered. First, a phase shift of 2δ is used to obtain a potential of the form, V(r) = V 0 cos ( 2k F r) (2k F r ) 3 . Secondly, the interplanar interaction is adjusted to reflect conditions that might hold when polytypic structures other than f.c.c. and h.c.p. occur. Results for the relative energies of the structures are presented. These results are compared with the observed structures of metallic elements and random solid solutions.

In situ transmission electron microscopy is an established experimental technique that permits direct observation of the dynamics and mechanisms of dislocation motion and deformation behavior. In this article, we detail the development of a novel specimen goniometer that allows real-time observations of the mechanical response of materials to indentation loads. The technology of the scanning tunneling microscope is adopted to allow nanometer-scale positioning of a sharp, conductive diamond tip onto the edge of an electron-transparent sample. This allows application of loads to nanometer-scale material volumes coupled with simultaneous imaging of the material’s response. The emphasis in this report is qualitative and technique oriented, with particular attention given to sample geometry and other technical requirements. Examples of the deformation of aluminum and titanium carbide as well as the fracture of silicon will be presented.

The use of solder to provide mechanical attachment and electrical interconnection for electronic packaging is widespread throughout the industry. One application for a lead-rich solder is in the IC chip/ceramic carrier connection. It is well-established that this joint is susceptible to thermal-fatigue failure and, hence, a thorough microstructural study is warranted. Previous work has shown that 95Pb-5Sn contains β-Sn precipitates that have formed upon solidification and subsequent aging at ambient temperature. Diffraction contrast TEM demonstrated that the precipitates lie on {111}pb habit planes. High-resolution electron microscopy was undertaken to establish whether or not the habit plane was faceted on the atomic level. This contribution reports on an observation of beam-induced precipitate dissolution.

It has long been established that in many metals, dislocation substructures (cell structures) develop in the grains during plastic deformation. More recently, it has been shown that, in low carbon steel, the dislocation substructures are closely related to active slip planes, i.e. to the grain orientation and loading conditions. Such a correlation gives rise to an effect of the strain history. This correlation may have an influence on the plastic behavior of prestrained samples and on their plastic stability. In fact, depending on the amplitude of the change of loading conditions, the subsequent stress can be deduced by the use of a generalized latent hardening concept accounting qualitatively for the substructures. On the other hand, during the reloading, some microbands may develop in the grains ; and the appearance of the microbands may be connected with the early occurrence of plastic instability. It is not known however, whether or not the dislocation substructure has an inherent importance, that is whether a heterogeneous distribution of dislocations is required to induce these features. Up to now, this point has not yet been made clear since the models used have only assumed changes in the critical shear stress values or qualitatively described the occurrence of ‘avalanche’ processes. The role of the formation and presence of such substructures on the subsequent behavior of materials requires better understanding.

Polycrystalline Ni/sub 3/Al-based intermetallic alloys have overcome their room temperature brittleness problem with a small amount or boron addition. Because of their unique strength-temperature relationship and good oxidation resistance at high temperatures, research efforts have been concentrated extensively on structural applications at elevated temperatures. In this paper the authors show that ductile Ni/sub 3/Al-B alloys also exhibit remarkable mechanical properties at cryogenic temperatures.

Orally administered ethanol produced dose-related suppression of IRI levels and elevation of IRG levels in fed and fasting rats. Plasma glucose levels were unaffected in the fasting rats, but a moderate hyperglycemic response accompanied the decline in IRI and the rise in IRG observed in the fed rats.

A new phase which precipitates from a parent matrix has a size and shape which reflects its difference from parent phase. If the lattice mismatch is significant, the elastic strain energy is more important than the surface energy in determining the morphology and the preferred habit plane. The preferred habit of a tetragonal inclusion in a cubic matrix has been predicted by minimizing the elastic strain energy as from the Ktachaturyan linear elastic formula.

The electronic packaging of integrated circuit chips has been cited as the limiting factor in the performance and reliability of high speed data processing units. A very important part of the package is in the first level where solder bonds the IC chip to a ceramic carrier. The most commonly used first level solder is 95Pb-5Sn. The importance of this solder connection instigated the following fundamental study of the microstructure of 95Pb-5Sn and its precipitates.The alloy was melted in vacuum at 400°C using 99.9% pure Pb and Sn. The ingot was allowed to cool and age for a few days at room temperature. TEM 3mm foils were cut and mechanically thinned down to 4 mil thickness. After aging at room temperature the solder is considered to be in its equilibrium state, no further changes in microstructure are observed.

Mesures par une technique d'ultrason du module de Young et du coefficient de Poisson entre 295 et 4K pour l'alliage Al-2,7 Cu-2,2 Li-0,12 Zr

A 'solid-state precipitation' process was used to prepare superconducting tapes containing Nb{sub 3}Al in a niobium matrix. Small ingots of Nb-(17-19 at.%)Al were prepared by arc melting, homogenizing, quenching, warm rolling into tape, and aging at 750-900 C to precipitate the A15 phase. Transmission electron microscopy studies revealed Nb{sub 3}Al precipitation in fine particles which formed a semicontinuous network over subgrain boundaries formed by the recovery of deformation-induced dislocations. Promising high-field critical currents were obtained (J{sub c}-10{sup 4} A/cm{sup 2} in a field of 14 T at 4.2 K).

A monolithic process has been used to produce superconducting materials by controlled precipitation of the A‐15 (V3Ga) phase inside the bcc matrix of a V‐rich solid solution. Ingots of V‐(17∼19 at.%)Ga were prepared by arc melting, homogenization, and quenching, were deformed at intermediate temperature into tape, and were aged at temperatures in the range 600–1000 °C to precipitate the A‐15 phase. The maximum critical transition temperature (∼14.8 °K) was found in materials aged at temperatures of 750 °C or below. At these aging temperatures the Tc initially increases with aging time, and passes through a distinct maximum. The source of the exceptionally high Tc is not clear, but may be attributable to a combination of high solute content and internal strain in the small A‐15 precipitate particles.

In this note a microcomputer-based system for multichannel scaling is described. This system relies on a combination of simple hardware with software support to achieve maximum cost effectiveness.