Rapidly solidified NiAl and FeAl

Melt spinning was used to produce rapidly solidified ribbons of the B2 intermetallics NiAl and FeAl. Both Fe-40Al and Fe-45Al possessed some bend ductility in the as spun condition. The bend ductility of Fe-40Al, Fe-45Al, and equiatomic NiAl increased with subsequent heat treatment. Heat treatment at approximately 0.85 T (sub m) resulted in significant grain growth in equiatomic FeAl and in all the NiAl compositions. Low bend ductility in both FeAl and NiAl generally coincided with intergranular failure, while increased bend ductility was characterized by increasing amounts of transgranular cleavage fracture

Tensile behavior of Fe-40Al alloys with B and Zr additions

Both Fe-40Al and Fe-40Al-0.1Zr with and without B were produced by the hot extrusion of powdered metal. Tensile properties were determined from room temperature to 1100 K in air. All of the materials possessed some ductility at room temperature, and addition of B caused an increase in ductility and a change in fracture mode from intergranular to transgranular cleavage. At high temperatures, failure was caused primarily by the formation of grain boundary cavities in all of the alloys. The effect of Zr addition was unclear because of the complexity of the various microstructures. Comparison of air and vacuum testing at high temperatures revealed that an apparent oxidation assisted mechanism reduced high temperature ductility in these alloys, especially at 900 K

College completion predicts lower depression but higher metabolic syndrome among disadvantaged minorities in young adulthood

College graduates enjoy healthier, longer lives compared with individuals who do not graduate from college. However, the health benefit of educational attainment is not as great for blacks as it is for whites. Moreover, college completion may not erase the detrimental effects of early-life disadvantage for blacks and Hispanics. We use nationally representative data on young adults to test whether American minorities experience differential returns to educational attainment. We find that college completion predicts lower rates of depression for all racial groups. It also predicts lower metabolic syndrome among whites. However, college completion predicts higher metabolic syndrome among black and Hispanic adults from disadvantaged backgrounds, suggesting upward mobility may come at a health cost to young minorities in America

Thermal Cycling and Isothermal Deformation Response of Polycrystalline NiTi: Simulations vs. Experiment

A recent microstructure-based FEM model that couples crystal-based plasticity, the B2 MB190 phase transformation and anisotropic elasticity at the grain scale is calibrated to recent data for polycrystalline NiTi (49.9 at.% Ni). Inputs include anisotropic elastic properties, texture and differential scanning calorimetry data, as well as a subset of recent isothermal deformation and load-biased thermal cycling data. The model is assessed against additional experimental data. Several experimental trends are captured - in particular, the transformation strain during thermal cycling monotonically increases and reaches a peak with increasing bias stress. This is achieved, in part, by modifying the martensite hardening matrix proposed by Patoor et al. [Patoor E, Eberhardt A, Berveiller M. J Phys IV 1996;6:277]. Some experimental trends are underestimated - in particular, the ratcheting of macrostrain during thermal cycling. This may reflect a model limitation that transformation-plasticity coupling is captured on a coarse (grain) scale but not on a fine (martensitic plate) scale

Characterization of a New Phase and Its Effect on the Work Characteristics of a Near-Stoichiometric Ni30Pt20Ti50 High-Temperature Shape Memory Alloy (HTSMA)

A new phase observed in a nominal Ni30Pt20Ti50 (at.%) high temperature shape memory alloy has been characterized using transmission electron microscopy and 3-D atom probe tomography. This phase forms homogeneously in the B2 austenite matrix by a nucleation and growth mechanism and results in a concomitant increase in the martensitic transformation temperature of the base alloy. Although the structure of this phase typically contains a high density of faults making characterization difficult, it appears to be trigonal (-3m point group) with a(sub o) approx. 1.28 nm and c(sub o) approx. 1.4 nm. Precipitation of this phase increases the microhardness of the alloy substantially over that of the solution treated and quenched single-phase material. The effect of precipitation strengthening on the work characteristics of the alloy has been explored through load-biased strain-temperature testing in the solution-treated condition and after aging at 500 C for times ranging from 1 to 256 hours. Work output was found to increase in the aged alloy as a result of an increase in transformation strain, but was not very sensitive to aging time. The amount of permanent deformation that occurred during thermal cycling under load was small but increased with increasing aging time and stress. Nevertheless, the dimensional stability of the alloy at short aging times (1-4 hours) was still very good making it a potentially useful material for high-temperature actuator applications

Re-Visiting SPEAR After 25 Years (Presentation material)

The SPEAR machine was completed in 1972. It consists of a single ring about 80 meters in diameter and started its very productive life as a positron-electron collider circulating beams up to 4 GeV. Synchrotron radiation research began almost immediately parasitically, then as half the program in the 1980s, and then became the whole program in 1991. The original network surveys used optical theodolites and invar tapes to place ring monuments in their ideal positions at constant offsets from the lines of ring quadrupoles. Optical tooling techniques were used to reference the monuments and survey offset targets on fixtures attached to the magnets. For more than 20 years neither the monuments nor magnets were restored to their ideal positions; the obvious discrepancies were simply ''feathered''. In 1992 SLC technology was used for the first time to re-measure the network and map the magnets. The discovery of many multiple-millimeter problems spurred planning for a 1995 global re-alignment. In 1995, all storage ring magnets and beamlines were mapped and moved. The band of displacements from ideal was reduced from about +/- 5mm to +/- 0.5mm. Upon start-up, beam stored without correctors

Optical Tooling with a Laptop Data Collector (Presentation material)

It has long been understood that the transposition of data from printouts to data collection sheets, and the subsequent manipulation of this data with measurement values, is an obvious error source in optical tooling projects. Ideas for computerized data collection have been under consideration for some time, yet they lacked the versatility needed for even the most typical optical tooling jobs. Surveyors experienced with optical tooling were used to designing the measurement strategy that worked best for each job. There was no canned formula that worked with every case. After extensive field testing a program was developed that worked in as many cases as possible. The program contains ideal files for components and monumentation, format sheets for set-up and measurement of components, and a summary sheet of work accomplished so far. This allows for the step by step movement through the measurement process

SLAC-PUB-9825 PEP-II Alignment *

The PEP-II Asymmetric B-factory consists of two independent storage rings, one located atop the other in the 2200m-circumference PEP tunnel. The high-energy ring, which stores a 9-GeV electron beam, is an upgrade of the existing PEP collider. It reutilizes all of the PEP magnets and incorporates a state-of-the-art copper vacuu

WinGEONET: What's New? (Presentation material)

The name GEONET means data reduction software for the accelerator alignment community. It was developed in the early 1980's but the only thing left from the original version is the hierarchical directory structure to hold the observations and results. This poster presents the three components of WinGEONET: the Windows interface, the computational engine and the visualization tool. It also presents further developments towards a more versatile toolbox architecture