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The effect of composition on the antiphase boundary (APB) energy of Ni-based L1(2)-ordered alloys is investigated by ab initio calculations employing the coherent potential approximation. The calculated APB energies for the {111} and {001} planes reproduce experimental values of the APB energy. The APB energies for the nonstoichiometric gamma' phase increase with Al concentration and are in line with the experiment. The magnitude of the alloying effect on the APB energy correlates with the variation of the ordering energy of the alloy according to the alloying element's position in the 3d row. The elements from the left side of the 3d row increase the APB energy of the Ni-based L1(2)-ordered alloys, while the elements from the right side slightly affect it except Ni. The way to predict the effect of an addition on the {111} APB energy in a multicomponent alloy is discussed., QC 20160720

Pancreatic amylin plays an important role in the control of nutrient fluxes and is an established therapy in human diabetes as it reduces post-prandial glucagon secretion and slows gastric emptying. Given the similar pathophysiology of human type-2 and feline diabetes mellitus, we investigated whether amylin reduces plasma glucagon levels in cats. Healthy cats were tested using an intravenous arginine stimulation test (IVAST), a meal response test with the test meal comprising 50% of average daily food intake, and an IV glucose tolerance test (IVGTT). Non-amyloidogenic rat amylin injected 5min before the respective stimulus significantly reduced plasma glucagon levels under all test situations. In the IVAST and IVGTT, cats treated with amylin also had lower plasma insulin concentrations. It was concluded that amylin does reduce plasma glucagon levels in cats, a feature that has treatment potential in diabetic animals as co-administration of amylin would reduce the insulin requirement to control glycaemia.

Titanium and titanium alloys are widely used for a variety of aerospace, chemical, marine, and other specialty applications because of their high strength, low density, good ductility, fatigue and corrosion resistance, as well as other properties. Depending on the application, a specific property (or combination of properties) can be obtained through microstructural modification. Microstructure evolution and control in titanium alloys is heavily dependent on the allotropic transformation from a hexagonal-close-packed crystal structure (denoted as alpha phase) found at low temperatures to a body-centered-cubic crystal structure (denoted as beta phase) at high temperatures. For pure titanium, this occurs at 882 deg C. In many titanium alloys, the beta phase is partially stabilized at lower temperatures, and the equilibrium volume fractions of alpha and beta vary with temperature. The temperature at which a specific alloy becomes entirely beta is called the beta transus. The conditions used for hot working and heating/heat treatment are often selected relative to the beta-transus temperature., Paper submitted to the ASM Handbook, v22 - Modeling and Simulation: Processing of Metallic Materials. Prepared in collaboration with Rolls-Royce Corporation, Indianapolis, IN. The original document contains color images. All DTIC reproductions will be in black and white.

Texture development during the subtransus hot forging of alpha/beta titanium alloys with an equiaxed-alpha microstructure was modeled using the Los Alamos Polycrystalline Plasticity (LApp) code and <111> pencil-glide polycrystalline plasticity code coupled with the finite-element-method (FEM) program DEFORM. The methodology treated the partitioning of the imposed strain between the alpha and beta phases, and thus enabled the prediction of the distinct deformation textures developed in the primary alpha and beta matrix during hot working. Two variant selection rules in conjunction with the beta deformation texture were also examined to establish a method for predicting the transformation texture of secondary alpha developed as a result of beta decomposition during cool-down following forging or heat treatment. The approach was validated via an industrial-scale trail comprising hot pancake forging of Ti-6Al-4V., Work unit no. M02R2000 Prepared in collaboration with Rolls-Royce Corporation, Indianpolis, IN., General Electric Aviation, Cincinnati, OH., Air Force Reseach Laboratory, Wright-Patterson AFB, OH.

The effect of alpha/beta solution temperature and cooling rate on the evolution of microstructure during the heat treatment of Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti6242Si) with a partially-spheroidized starting microstructure of equiaxed + remnant lamellar alpha was established. Experiments comprising induction heating to a peak temperature of 971 or 982 degrees C followed by cooling at a rate of 11 or 42 degrees C/min revealed that the volume fraction of the equiaxed alpha grew much more rapidly than the lamellar constituent. These results were explained semi-quantitatively using simple diffusion analyses of the growth of either spherical or elliptical particles, taking into account the soft-impingement of the concentration fields. Despite the much lower diffusivity of molybdenum, which appears to control the growth of primary alpha in Ti6242Si, the similarity of the overall kinetics compared to those measured previously for Ti-6Al-4V was explained on the basis of the higher supersaturations developed during cooldown in the present alloy., Submitted to the Jnl. of Metallurgical and Materials Transactions. Prepared in collaboration with Drexel Univ., Dept. of Materials Science and Engineering, Philadelphia, PA., Dayton Univ., Dayton OH., and the Rolls-Royce Corp., Indianapolis, IN.

The development of refined microstructures for dispersion strengthening of Aluminum alloys by rapid solidification is related to the undercooling at nucleation and during competitive crystal growth. With controlled droplet samples the important processing parameters that govern undercooling in the powders have been identified and include powder size and coating melt cooling rate and superheat. The droplet method has yielded measured undercoolings of 175 C for AL and values near 300 C for some AL alloys. Droplet studies have been valuable in examining the solidification pathways including thermal history effects associated with rapid solidification and dispersoid formation in Aluminum-Nickel, Aluminum-Iron, and Aluminum-Beryllium alloys. Based on the analysis of solidification pathways, microstructure maps may be developed to identify the processing that can yield fine-scale eutectics, metastable structures or suppression of coarse primary intermetallic phases which are useful for the development of dispersoid structures. (jg)