Search

The deformation of polycrystalline uranium 6 wt pct niobium (U6Nb) was studied in situ during uniaxial tensile loading by time-of-flight neutron diffraction. Diffraction patterns were recorded at incremental stresses to a maximum of 450 MPa (∼4 pct macroscopic strain). Consistent with reorientation of the martensite variants by twinning, significant changes in the diffraction peak intensities, which were proportional to the plastic contribution of the macroscopic strain, were observed. Both the lattice parameters (a, b, c, and γ) and interplanar spacings (dhkl) were determined as a function of applied stress. Phenomenologically, the highly anisotropic stress response of the lattice parameters as well as the individual lattice spacings can be related to deformation twinning. Preliminary transmission electron microscopy (TEM) studies identified the (\(\bar 1\)30) and (\(\bar 1\)72) as active deformation twinning systems of U6Nb in tension.

An investigation of the microstructures of four U–Nb alloys has been conducted. The nominal Nb contents are 5, 9, 13 and 18at.% (approximately 2, 4, 5.5 and 8 wt%). The self-accommodating twin structures have been characterized and considered in terms of the lattice parameters of the martensite phases as well as the tetragonal distortion associated with the previously proposed intermediate γ0 phase. In addition, active deformation twinning systems during deformation of the U–13 at.% Nb shape-memory alloy have been identified and are discussed with respect to the α'' monoclinic distortion and ease of propagation in the microstructure.

We have completed a comparative X-ray diffraction (XRD) and Finite Element Analysis (FEA) study of Inconel 718 clad Tungsten tubes, of relevance to the Accelerator Production of Tritium (APT) program at the Los Alamos National Laboratory (LANL). Because the Inconel cladding must be in intimate contact with the tungsten at operating temperatures, the materials are diffusion bonded by Hot Iso-static Pressing (HIP) at 1080°C. However, the difference in thermal expansion coefficients of inconel 718 and tungsten produce large residual stresses upon cooling. The classical XRD (d vs. sin 2 ψ) technique was used to determine the stresses in the outer layer of inconel 718. These results are used to benchmark Finite Element Analysis (FEA) calculations, and a direct comparison is made in this paper.

The Hylebos Waterway is an industrialized waterway ofCommencement Bay, Tacoma, Washington, that is severelycontaminated with aromatic and chlorinatedhydrocarbons in the sediment. Juvenile chinook (Oncorhynchus keta) and chum salmon (O.tshawytscha) inhabit this waterway for a few days orweeks during their outmigration from freshwaterstreams to saltwater. The purpose of thisinvestigation was to determine to what degree juvenilechum and chinook salmon captured from the HylebosWaterway might bioaccumulate organic contaminants. These levels of exposure will be compared to previousstudies where such exposures have been linked tobiological dysfunction in juvenile salmon. Theresults showed that juvenile chum and chinook salmonfrom the Hylebos Waterway take up a wide range ofchemical contaminants, compared to fish fromhatcheries or reference estuaries. These contaminantsinclude high and low molecular weight polycyclicaromatic hydrocarbons (PAHs), polychlorinatedbiphenyls (PCBs, including the toxic congeners 105 and118), hexachlorobutadiene (HCBD), hexachlorobenzene(HCB), DDTs, heptachlor, and several pesticides. Immunohistochemical examination of the gill and gut injuvenile chum salmon from the Hylebos Waterway showedthe induction of the P450 metabolizing enzyme. Moreover, concentrations of contaminants in juvenilechinook and chum salmon from the Hylebos Waterway arecomparable to levels previously shown to be associatedwith biological injury in juvenile chinook salmon,such as impaired growth, suppression of immunefunction as demonstrated by reduced B cell function,and increased mortality following pathogen exposure.

In most engineered reservoirs the water to extract the geothermal energy must be supplied, i.e., forced into the reservoir, rather than merely extracted as is common for conventional geothermal reservoirs. One operational hydraulic parameter of great interest is the impedance, which measures how much pressure is required to force water at unit flow rate through the reservoir. For practical purposes, the impedance should be less than 1 MPa s/l, and economic competitiveness with conventional reservoirs requires values one tenth as large. Most engineered reservoirs operated to date have met the upper requirement, and some are approaching the lower. Another parameter of great practical interest is the water loss rate, i.e. the difference between the rates of water injected and produced. Water losses and impedance are very pressure-dependent, but impedance is inversely so—high pressure increases water loss, but decreases the impedance. Hence operators may select strategies to meet their requirements. In some tight rock formations such as those at the Fenton Hill, USA, reservoir, the water loss rate may be so small that the pressure may be maximized to reduce impedance and increase energy production. In more permeable rock formations, the water losses may be quite high, so pressure and energy production may have to be limited. But in some cases, e.g. the reservoir at Soultz, France, there may be enough native permeability and water in place that more water actually may be extracted with downhole pumps from the reservoir than is injected.

The modern HDR concept originated at the Los Alamos National Laboratory and was first demonstrated at Fenton Hill, New Mexico (USA). Experience gained during the development of the deeper HDR reservoir at Fenton Hill clearly showed that HDR reservoirs are formed by opening pre-existing, but sealed, multiply-connected joint sets. Subsequent flow testing indicated that sustained operation of HDR systems under steady-state conditions is feasible. The most significant remaining HDR issues are related to economics and locational flexibility. Additional field test sites are needed to advance the understanding of HDR technology so that the vast potential of this resource can be economically realized around the world.

A large amount of fluid circulation and heat extraction (i.e., thermal power production) research and testing has been conducted on engineered geothermal reservoirs in the past 15 years. In confined reservoirs, which best represent the original Hot Dry Rock concept, the flow distribution at any given time is primarily determined by three parameters: (1) the nature of the interconnected network of pressure-stimulated joints and open fractures within the flow-accessible reservoir region, (2) the mean pressure in the reservoir, and (3) the cumulative amount of fluid circulation—and therefore reservoir cooling—that has occurred. For an initial reservoir rock temperature distribution and mean fluid outlet temperature, the rate of heat extraction (i.e., thermal power) is at first only a function of the production flow rate, since the production temperature can be expected to remain essentially constant for some time (months, or even years). However, as reservoir circulation proceeds, the production temperature will eventually start to decline, as determined by the mean effective joint spacing and the total flow-accessible (i.e., heat-transfer) volume of the reservoir. The rate of heat extraction, which depends on the production flow rate, can also vary with time as a result of continuing changes in the flow distribution arising from reservoir cooling. The thermal power of engineered reservoirs can most readily be increased by increasing the production flow rate, as long as this does not lead to premature cooldown, the development of short-circuit flow paths, or excessive water losses. Generally, an increase in flow rate can be accomplished by increasing the injection pressure within limits. This strategy increases the driving pressure drop across the reservoir and the mean reservoir pressure, which in turn reduces the reservoir flow impedance by increasing the amount of joint dilation. However, the usefulness of this strategy is limited to reservoir operating pressures below the fracture extension pressure, and may lead to excessive water losses, particularly in less-confined reservoirs. Under such conditions, a downhole production-well pump may be employed to increase productivity by recovering more of the injected fluid at lower mean reservoir operating pressures.

Polycrystalline structural materials often contain inherent stresses that partition across the microstructure. From composites to fabricated components, stress and strain fields are often highly heterogeneous at the microstructural level, contrary to the inferences commonly made in continuum mechanics. Since these “residual” stresses are intimately linked to failure processes, one of the challenges in modeling constitutive behavior is to predict the magnitude of the stress heterogeneities in polycrystals and thus understand the implications.

The National Benthic Surveillance Project (NBSP), a component of NOAA's National Status and Trends Program, monitored sediment and bottomfish for chlorinated hydrocarbon pesticides (CHs), PCBs and polycyclic aromatic hydrocarbons (PAHs) at selected urban and nonurban sites along the west coast of the USA from 1984 to 1993. This project successfully generated an extensive data set to evaluate the recent status and trends of environmental quality in coastal waters. This article summarizes and interprets the status of selected PAHs, PCBs and CHs in surficial sediments and selected species of bottom-feeding fish for 50 sites in Alaska, Washington, Oregon and California for the first 7 years (1984–1990) of the NBSE. The highest concentrations of most sediment-associated organic contaminants were present in the most highly urbanized areas, and many of the organic contaminants were bioaccumulated by indigenous marine fish species. The concentrations of PAHs and CHs in sediments generally correlated with levels of these compounds or their derivatives in bottom-dwelling fish. Assessment of trends in the concentrations of chlordanes, dieldrin, DDTs, PAHs and PCBs for the 7 year period from 1984–1990 suggest that, since the mid-1980s, concentrations of the persistent CHs, such as PCBs and DDTs in sediment and fish, show no consistent temporal trends, whereas levels of PAHs, which are nonpoint source contaminants, showed consistent increases at both nonurban and urban near-coastal sites.

ULTIMET® alloy is a metastable face-centered-cubic (FCC) material that undergoes a deformation-induced phase transformation to a hexagonal-close-packed (HCP) phase. In-situ neutron-diffraction measurements were made at room temperature to study the phase transformation during monotonic tensile deformation to a total strain of 16% (890 MPa) and also during strain-controlled cyclic deformation with a total strain range of Δe=2.5% up to 500 fatigue cycles. The HCP phase developed with increasing strain during the monotonic-loading experiment, while, during the fatigue deformation, the HCP phase continuously developed with each loading cycle. Transmission electron microscopy was also performed on monotonically loaded specimens in order to complement the neutron-diffraction results.

The evolution of elastic lattice strain in a Ti–48Al–2W (at.%) alloy, subjected to (1) quasistatic tensile loading and (2) constant-load tensile creep, was investigated at 1033K using in situ neutron diffraction. During the quasistatic test to a maximum stress of 435MPa, a- and c-axes lattice strains increased linearly with a small degree of anisotropy (E¯a∕E¯c≅0.9) up to 200MPa, followed by a significant redistribution of load above 260MPa due to the plastic anisotropy. Time-resolved in situ measurements were also performed during the creep at 276 and 327MPa. The results show that lattice strain evolution during the primary creep is qualitatively similar to the quasistatic case under the current test conditions.

In this paper, we report for the first time, to our knowledge, spatially resolved measurements of strain gradients across a grain containing twins, located in the bulk of a polycrystalline Mg AZ31 sample. We also report orientation mapping on three parallel sections from the bulk of the sample. We use for such purpose the technique of differential-aperture X-ray microscopy (DAXM) based on synchrotron X-rays. The DAXM technique allows us to map crystallographic strains with sub-micron-sized spatial resolution. The results of this experiment confirm indirect evidence from previous experiments having less spatial resolution that important stress gradients exist in the vicinity of twin boundaries. Such a result is relevant to understanding twin growth and de-twinning, since both mechanisms are affected by stress-driven twin dislocations at the interface. � 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Juvenile chinook salmon (Oncorhynchus tshawytscha) were sampled in Puget Sound, Washington, for 2 consecutive years from contaminated urban estuaries, a nonurban estuary, and from the respective hatcheries to assess exposure to anthropogenic chemicals and to determine if biochemical changes were occurring as a consequence of exposure. Exposure to polycyclic aromatic hydrocarbons (PAHs), chlorinated hydrocarbons, and butyltins was determined. The mean concentrations of PAHs and PCBs in stomach contents and PCBs in liver were significantly higher in salmon from the urban estuaries compared to fish from the nonurban estuary in both sampling years. Higher hepatic concentrations of PCBs than DDTs were found in fish from the urban estuaries, but butyltins were rarely detected. Further, mean concentrations of fluorescent aromatic compounds in bile, an estimate of exposure to PAHs, and hepatic cytochrome P4501A and levels of hepatic DNA adducts were also significantly higher in salmon from the urban estuaries compared to either the nonurban estuary or the hatcheries. Results demonstrated increased exposure to chemical contaminants in outmigrant juvenile salmon during their relatively brief residence in urban estuaries of Puget Sound. Moreover, the exposure was sufficient to elicit biochemical responses, which suggest a potential for other biological effects to ensue.

Linear Friction Welding (LFW) is a solid phase bonding process, which is being used commercially for fabrication of complex titanium parts. Like other welding processes, LFW joints contain tensile residual stresses that could negatively impact performance. This paper presents results from recent residual stress measurements on a test specimen containing a linear friction weld. Residual stress measurements were performed on the test specimen using the contour method and neutron diffraction. A comparison of the data from the two techniques is provided, which is favorable. In general, the residual stresses from the LFW process are shown to be high in magnitude and localized near the weld.

At high pressures zirconium is known to undergo a phase transformation from the hexagonal close packed (HCP) alpha phase to the simple hexagonal omega phase. Under conditions of shock loading, the high-pressure omega phase is retained upon release. However, the hysteresis in this transformation is not well represented by equilibrium phase diagrams and currently models that accurately represent such a solid-solid phase transformation coupled with the multi-phase plasticity likely under shock conditions do not exist. For this reason, the influence of peak shock stress on the retention of omega phase in Zr is explored in this study. In-situ VISAR measurements along with post-mortem metallographic and neutron diffraction characterization of soft recovered specimens have been utilized to quantify the volume fraction of retained omega phase, morphology of the shocked alpha and omega phases, and qualitatively understand the kinetics of this transformation. This understanding of the role of peak shock stress will be utilized to address physics to be encoded in our present macro-scale models.

We show that a variety of bulk metallic glasses (BMGs) inherit their Young's modulus and shear modulus from the solvent components. This is attributed to preferential straining of locally solvent-rich configurations among tightly bonded atomic clusters, which constitute the weakest link in an amorphous structure. This aspect of inhomogeneous deformation, also revealed by our in situ neutron diffraction studies of an elastically deformed BMG, suggests a rubberlike viscoelastic behavior due to a hierarchy of atomic bonds in BMGs.

In early 1977, the condition of the two deep boreholes at Fenton Hill was as follows: The GT-2 borehole had been drilled to a depth of 9,619 ft (2,832 m) and a 7 5/8-in. scab liner had been placed and cemented from 8,973 ft to 9,581 ft, leaving a 38-ft “rat hole” below the liner (see Fig. 3.12). The EE-1 borehole had been drilled to a depth of 10,053 ft (3,064 m) and cased from 9,599 ft to the surface with a composite casing string (999 ft of 7 5/8-in. casing from 9,599 to 8,600 ft, and 8 5/8-in. casing above 8,600 ft—see Fig. 3.26).

The world’s first demonstration of the hot dry rock (HDR) geothermal energy concept took place at Fenton Hill, New Mexico, in the mid to late 1970s. The objective was to create a large, man-made HDR reservoir in rock at an appropriate temperature (~200°C) and accessed by two deep boreholes, completing the pressurized earth circulation loop.

The concept of hot dry rock (HDR) geothermal energy originated at the Los Alamos National Laboratory. In 1970 it was proposed as a method for exploiting the heat contained in those vast regions of the earth’s crust that contain no fluids in place—by far more widespread than natural geothermal resources (HDR represents over 99% of the total U. S. geothermal resource). Although often confused with the small, already mostly commercialized hydrothermal resource, HDR geothermal energy is completely different from hydrothermal energy.

The Phase I reservoir at Fenton Hill, which extended over the approximate depth interval 8,000–10,000 ft, had indeed demonstrated the technical feasibility of the HDR concept, but at a temperature (157°C) and thermal power (3 MW) lower than desirable for commercial power production. The Phase II reservoir was planned for development at a depth of 12,000–14,000 ft, to test the HDR concept at a temperature and rate of geoheat production more appropriate for a commercial power plant, and with a reservoir large enough to sustain a high level of thermal power for an extended period (at least 10 years).

With the very difficult task of directionally drilling the lower portions of the EE-2 and EE-3 boreholes complete, in early 1982 the critical next step in the development of the Phase II reservoir began. Recall that at this time, the theory that a penny-shaped, vertical hydraulic fracture could be created in jointed basement rock still held sway with the HDR Project management (although many of the Project staff had by then abandoned it). This, of course, was why the lower portions of EE-2 and EE-3 had been inclined 35° from the vertical by costly and time-consuming directional drilling, with EE-3 terminating about 1,200 ft vertically above EE-2. Mort Smith, in his Abstract for the 1982 Annual Report (HDR 1983b), stated that “During Fiscal 1982, emphasis in the Hot Dry Rock Program was on development of methods to produce the hydraulic fractures required to connect the deep, inclined wells of the Phase II system at Fenton Hill.”

In the wake of initial Phase II reservoir testing and the ICFT, fundamental questions about the commercial potential of HDR technology remained to be answered. How reliable is power production from an HDR reservoir? What might be the longevity of such a reservoir? To answer these questions, and to demonstrate that geothermal energy could be extracted on a sustained basis, more extensive testing would be required. The Long-Term Flow Test (LTFT) for the Fenton Hill Phase II reservoir was designed to simulate as closely as possible the conditions under which a commercial HDR power plant might operate.

As detailed in preceding chapters, the technical feasibility of HDR geothermal energy was clearly demonstrated at Fenton Hill, with the testing of two separate confined reservoirs. The major task now in view is moving this revolutionary new technology to its appropriate place in the world’s energy supply mix. Obviously, technical feasibility is not enough: HDR must also be capable of supplying useful amounts of energy economically. For that requirement to be met, several issues—which have yet to be adequately addressed—will need to be resolved.

Following the ICFT, work began to complete the design and installation of a permanent surface plant for the Long-Term Flow Test (LTFT), which was planned as a realistic demonstration of the viability of HDR technology under conditions closely approximating those of a commercial HDR power facility. The major difference was that no power would be produced (the thermal energy brought to the surface during circulation would simply be wasted to the atmosphere). The decision not to produce power was based on the following considerations

How far back in our past did humans begin to use hot water and steam coming from vents in the earth’s surface to improve their lives? Did they make stops at such sites while moving from place to place, bathing in the warm pools or using the waters for cooking, and eventually construct villages near hot springs? We can only imagine in what ways man first availed himself of the earth’s heat; but we can assume that human populations in various areas sooner or later encountered hot waters that were bubbling up to the surface after having been raised to high temperatures by circulation through deep, hot rock—and that they made use of the heated water.

The demonstration of flow connectivity between the redrilled EE-3A wellbore and the EE-2 reservoir zone (Expts. 2059 and 2062) made it clear that a viable HDR system had finally been established, although that stage of the Fenton Hill HDR Project took about 5 years (1980–1985)—much longer than originally anticipated. Throughout that period, Germany and Japan contributed both funds and manpower to the effort. The Germans withdrew from the Project at the end of 1985, but the Japanese maintained a presence through the following year. In early 1986, they began pressing strongly for the thermal and flow characteristics of the HDR system to be evaluated.

Students entering the first year of nine combined baccalaureate‐MD degree (CD) programs were administered the Matriculating Student Questionnaire (MSQ) of the Association of American Medical Colleges. A profile of the CD students’ perspectives on becoming a physician was compared with the profile of traditional medical students who responded to the MSQ. CD students chose medicine as a career goal earlier in life than their traditional counterparts. They also had more positive perceptions of medicine. Their decisions regarding future career interests in medicine differed in some respects from those of traditional students. Larger percentages of CD students were female, had Asian backgrounds, and had physician fathers. The views of CD students were partly related to the type of CD program they attended and to demographic/background characteristics, including age, which was suggested by preliminary comparisons between premedical students and CD students.

Magnesium alloys are unique materials because tensile twinning and de-twinning can be easily activated, which leads to rapid texture and hardening evolution [1]. Here we present a study of the mechanical response of a magnesium alloy (AZ31) when deformed under twinning dominated conditions, i.e. uniaxial compression along prior extrusion axis. In-situ neutron diffraction measurements were carried out using the SMARTS (Spectrometer for Materials Research at Temperature and Stress) instrument at LANSCE (Los Alamos Neutron Science Center) [2].

This report, the third in a four-part series, summarizes significant research projects performed by the U.S. Department of Energy (DOE) over 30 years to overcome challenges in reservoir engineering and to make generation of electricity from geothermal resources more cost-competitive.

A novel capability was designed, implemented, and tested for in situ neutron diffraction measurements during loading at cryogenic temperatures on the spectrometer for materials research at temperature and stress at Los Alamos National Laboratory. This capability allowed for the application of dynamic compressive forces of up to 250 kN on standard samples controlled at temperatures between 300 and 90 K. The approach comprised of cooling thermally isolated compression platens that in turn conductively cooled the sample in an aluminum vacuum chamber which was nominally transparent to the incident and diffracted neutrons. The cooling/heat rate and final temperature were controlled by regulating the flow of liquid nitrogen in channels inside the platens that were connected through bellows to the mechanical actuator of the load frame and by heaters placed on the platens. Various performance parameters of this system are reported here. The system was used to investigate deformation in Ni-Ti-Fe shape memory alloys at cryogenic temperatures and preliminary results are presented.

Chemical pollution at sites in or near San Diego Bay was investigated between 1984 and 1988. The mean concentrations of selected polychlorinated biphenyls (PCBs), metals (e.g., copper and lead), and aromatic hydrocarbons in sediments from sites in the southern and central portions of the bay were significantly higher (p≤0.05) than those in sediment samples from nearby nonurban sites

High concentrations of toxic chemicals in sediment and white croaker (Genyonemus lineatus), as well as liver diseases (e.g., carcinomas) in this species, were found in the Los Angeles area. The highest concentrations of aromatic hydrocarbons (AHs) in the sediment were in San Pedro Bay, and the highest concentrations of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) derivatives were in sediment from near the White Point sewer outfall. Concentrations of AHs, polychlorobiphenyls (PCBs), and DDT derivatives were generally higher in food organisms from the croaker's stomach than in sediment. Moreover, croaker from San Pedro Bay and White Point were substantially contaminated with DDT derivatives and metabolites of aromatic compounds, compared to croaker from the Hyperion outfall and Dana Point. The evidence suggest that the observed pathological conditions of the liver were associated with exposure of the croaker to toxic chemicals, which occurred, at least in part, through the ingestion of contaminated food organisms.

This is an in situ measurement of the full stress tensor and its evolution in a growing deformation twin and, simultaneously, in the grain where the twin forms. The combined information provides a detailed picture of the grain-twin interaction. The three-dimensional x-ray diffraction method using 80.7 keV synchrotron x rays allows us to in situ investigate a grain within the bulk of a magnesium alloy (AZ31) sample that is compressed to activate the ${10\overline{1}2}⟨\overline{1}011⟩$ tensile twin system. We observe that the stress state of the twin is drastically different from the one of the grain in which it is embedded. We analyze such result in terms of the shear transformation associated with twinning and the dimensional constraints imposed by the surrounding aggregate.

In situ synchrotron and neutron diffraction were used to study deformation mechanisms in Ni over a broad range of grain sizes. The experimental data show that unlike in coarse-grained metals, where the deformation is dominated by dislocation slip, plastic deformation in nanocrystalline Ni is mediated by grain-boundary activities, as evidenced by the lack of intergranular strain and texture development. For ultrafine-grained Ni, although dislocation slip is an active deformation mechanism, deformation twinning also plays an important role, whose propensity increases with the grain size.

The performance of ferroelectric ceramics is governed by the ability of domains to switch. A decrease in the switching ability can lead to degradation of the materials and failure of ferroelectric devices. In this work the dynamic properties of domain reorientation are studied. In situ time-of-flight neutron diffraction is used to probe the evolution of ferroelastic domain texture under mechanical cyclic loading in bulk lead zirconate titanate ceramics. The high sensitivity of neutron diffraction to lattice strain is exploited to precisely analyze the change of domain texture and strain through a full-pattern Rietveld method. These results are then used to construct a viscoelastic model, which explains the correlation between macroscopic phenomena (i.e. creep and recovered deformation) and microscopic dynamic behavior (i.e. ferroelastic switching, lattice strain).

A consistent and statistically significant association between prevalence of hepatic neoplasms in free-living sole (Parophrys vetulus) and levels of anthropogenic polycyclic aromatic hydrocarbons in bottom sediment from sites of fish capture was documented in a series of studies conducted over a period of 7 years in Puget Sound, Washington. This result strengthens the evidence supporting a causal relationship between exposure to sediment-associated hydrocarbons and development of hepatic neoplasms in this bottom-dwelling marine fish species. Prevalences of two other distinct categories of idiopathic hepatic lesions-megalocytic hepatosis and steatosis/hemosiderosis-also showed consistent, statistically significant associations with polycylic aromatic hydrocarbon concentrations in bottom sediment, and association with prevalence of a third category (putatively preneoplastic foci of cellular alteration) approached statistical significance. On the basis of other studies, megalocytic hepatosis and foci of cellular alteration are both considered to be important precursor lesions in the stepwise histogenesis of hepatic neoplasms.

We have conducted in situ high-pressure diffraction experiments on depleted uranium (DU-238) at pressures up to $8.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and temperatures up to $1123\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. From the pressure $(P)$-volume $(V)$-temperature $(T)$ measurements, thermoelastic parameters were derived for $\ensuremath{\alpha}$-uranium based on a modified high-$T$ Birch-Murnaghan equation of state and a thermal-pressure approach. With the pressure derivative of the bulk modulus ${K}_{0}^{\ensuremath{'}}$ fixed at 4.0, we obtained ambient bulk modulus ${K}_{0}=117(2)\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, temperature derivative of bulk modulus at constant pressure ${(\ensuremath{\partial}K∕\ensuremath{\partial}T)}_{P}=\ensuremath{-}3.4(4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}∕\mathrm{K}$ and at constant volume ${(\ensuremath{\partial}K∕\ensuremath{\partial}T)}_{v}=\ensuremath{-}1.1(6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}∕\mathrm{K}$, volumetric thermal expansivity ${\ensuremath{\alpha}}_{T}=a+bT$, with $a=1.2(\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\phantom{\rule{0.3em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ and $b=8.0(\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\phantom{\rule{0.3em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$, and the pressure derivative of thermal expansion ${(\ensuremath{\partial}\ensuremath{\alpha}∕\ensuremath{\partial}P)}_{T}=\ensuremath{-}2.5(5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\phantom{\rule{0.3em}{0ex}}{\mathrm{GPa}}^{\ensuremath{-}1}\phantom{\rule{0.2em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$. Within the experimental errors, the ambient bulk modulus and volumetric thermal expansion derived from this work are in good agreement with previous experimental results, whereas all other thermoelastic parameters represent the first determinations for the $\ensuremath{\alpha}$ phase of uranium. We also studied the $\ensuremath{\alpha}\text{\ensuremath{-}}\ensuremath{\gamma}$ phase transformation and obtained a phase boundary described by $T$ $(\text{in}\phantom{\rule{0.3em}{0ex}}\mathrm{K})=1032+7.4P\phantom{\rule{0.3em}{0ex}}(\text{in}\phantom{\rule{0.3em}{0ex}}\mathrm{GPa})$. Although the $\ensuremath{\gamma}$-phase uranium cannot be pressure quenched to ambient conditions, it was observed to be stable upon cooling from $1123\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ at pressures of $7--8\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. These observations indicate that pressure, in addition to the commonly utilized alloying techniques, provides an alternative route for stabilizing the $\ensuremath{\gamma}$-uranium at room temperature.

The in situ time-of-flight neutron-diffraction measurements captured well the martensitic transformation behavior of the Ni-Mn-Ga ferromagnetic shape-memory alloys under uniaxial stress fields. We found that a small uniaxial stress applied during phase transformation dramatically disturbed the distribution of variants in the product phase. The observed changes in the distributions of variants may be explained by considering the role of the minimum distortion energy of the Bain transformation in the effective partition among the variants belonging to the same orientation of parent phase. It was also found that transformation kinetics under various stress fields follows the scale law. The present investigations provide the fundamental approach for scaling the evolution of microstructures in martensitic transitions, which is of general interest to the condensed matter community.

In-situ neutron diffraction during cyclic tension-compression loading (∼+3.5% to −2.8%) of a 17Mn-3Al-2Si-1Ni-0.06C steel that exhibits concurrent transformation and twinning -induced plasticity effects indicated a significant contribution of intragranular back stresses to the observed Bauschinger effect. Rietveld analysis revealed a higher rate of martensitic transformation during tension compared to compression. Throughout cycling, α′-martensite exhibited the highest phase strains such that it bears an increasing portion of the macroscopic load as its weight fraction evolves. On the other hand, the e-martensite strain remained compressive as it accommodated most of the internal strains caused by the shape misfit associated with the γ→e and/or e→α′ transformations.