Determination of the long-term intergranular corrosion rate of stainless steel in concentrated nitric acid

Stainless steels with low carbon content and free from any precipitation undergo intergranular attack in hot nitric acid. The corrosion rate measured by weight loss requires prolonged immersion testing to reach the apparent steady state corrosion, which coincides with the onset of grain dropping. A more appropriate method for predicting the long-term penetration rate is described in this study. A close observation and a statistical analysis of the attack grooves were firstly undertaken using immersion testing. The major findings are an outstanding morphology of the grooves with flat planes and preserved angle even after the onset of grain dropping, as well as a constant rate of the penetration into the surface. The formation of the grooves could then be represented by a geometrical model put forward by Beaunier and co-workers. Consequently, the method proposed for predicting the penetration rate consists in measuring the depth and the angle of the grooves obtained in short time immersion testing. Multiplying the penetration rate calculated from the previous data by the ratio between the penetration depth and the length of the grain boundary path does give an accurate long-term penetration rate. The method has been shown to apply successfully to AISI 304L stainless steel in several nitric solutions.     

Phase relations in the ternary Cu-Ga-In system

The phase relations of the Cu-Ga-In system were investigated in a composition range which is relevant for the production of Cu(In,Ga)Se₂ based thin film solar cells. The alloys Cu₁₆(In_{1 − y}Ga_y)₉, Cu₉(Ga,In)₄ and elemental In could be identified as the equilibrium phases of a ternary subsystem in the Cu-Ga-In phase diagram. The coexisting phases are well developed until 220 °C. In the case of Cu₉Ga₄ it is remarkable that the solubility of In in Cu₉Ga₄ highly increases with increasing temperature. Consequences for the selenization of metallic Cu-In-Ga precursors are discussed.     

A numerical algorithm for efficiently obtaining a Feynman parameter representation of one-gluon loop QCD Feynman diagrams for a large number of external gluons

A numerical program is presented which facilitates a computation pertaining to the full set of one-gluon loop diagrams (including ghost loop contributions), with M attached external gluon lines in all possible ways. The feasibility of such a task rests on a suitably defined master formula, which is expressed in terms of a set of Grassmann and a set of Feynman parameters. The program carries out the Grassmann integration and performs the Lorentz trace on the involved functions, expressing the result as a compact sum of parametric integrals. The computation is based on tracing the structure of the final result, thus avoiding all intermediate unnecessary calculations and directly writing the output. Similar terms entering the final result are grouped together. The running time of the program demonstrates its effectiveness, especially for large M.

Program summary

Program title:DILOG2Program identifier:ADXN_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXN_v1_0Program obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandProgramming language:FORTRAN 90Computer(s) for which the program has been designed:Personal ComputerOperating system(s) for which the program has been designed: Windows 98, XP, LINUXNumber of processors used:oneNo. of lines in distributed program, including test data, etc.:2000No. of bytes in distributed program, including test data, etc.:16 249Distribution format:tar.gzExternal routines/libraries used:noneCPC Program Library subprograms used:noneNature of problem:The computation of one gluon/ghost loop diagrams in QCD with many external gluon lines is a time consuming task, practically beyond reasonable reach of analytic procedures. We apply recently proposed master formulas towards the computation of such diagrams with an arbitrary number (M) of external gluon lines, achieving a final result which reduces the problem to one involving integrals over the standard set, for given M, of Feynman parameters.Solution method:The structure of the master expressions is analyzed from a numerical computation point of view. Using the properties of Grassmann variables we identify all the different forms of terms that appear in the final result. Each form is called “structure”. We calculate theoretically the number of terms belonging to every “structure”. We carry out the calculation organizing the whole procedure into separate calculations of the terms belonging to every “structure”. Terms which do not contribute to the final result are thereby avoided. The final result, extending to large values of M, is also presented with terms belonging to the same “structure” grouped together.Restrictions:M is coded as a 2-digit integer. Overflow in the dimension of used array is expected to appear for M?20 in a processor that uses 4-bytes integers or for M?34 in a processor with 8-bytes integers.Running time:Depends on M, see enclosed figures.     

Models of closed multimachine computer systems with transient-fault-tolerance and fault-tolerance on the basis of replication under byzantine faults

Consideration was given to the key definitions, notions, and models that may be useful for transient-fault-tolerant and fault-tolerant computing in the unmanned multimachine computer systems having many interconnected autonomous computers without shared memory and centralized control organ and operating with high degree of computational parallelism, that is, executing on different computers simultaneously various tasks which interchange their information. These computations should establish reliable results under byzantine faults and controllable degradation of the system at detection of faults.     

Silver surface enrichment controlled by simultaneous RBS for reliable PIXE analysis of ancient coins

Evidence of silver surface enrichment of ancient silver-copper coins has been pointed out in the past years. Surface enrichment can be fortuitous or intentional. In this paper, we have investigated the cleaning procedures usually performed after excavation or in museums. We have shown that chemicals or commercial products routinely used dissolve preferentially the copper phase and consequently contribute to the silver surface enrichment. As a result, surface analyses such as PIXE or XRF can be strongly affected by this effect. By using simultaneously RBS and PIXE, it is possible to check through the silver surface enrichment and then select the reliable measurements, characteristic of the bulk composition. Results on coins recently discovered and mechanically or chemically cleaned are presented.     

Alloying and microstructure stability in the high-temperature Mo-Si-B system

Multi-phase alloys in the Mo-Si-B system are identified as high-temperature structural materials due to their high melting points (above 2000 °C) and excellent oxidation resistance attributed to the self-healing characteristics of borosilica layer up to 1400 °C. In the current study, the effect of alloying additions to achieve a reduced weight density has been examined in terms of changes in the microstructure and phase stability. The critical factor underlying the microstructural changes is related to the influence of the alloying additions on the stability of the high melting temperature ternary-based Mo₅SiB₂ (T₂) borosilicide phase.     

Microstructural and mechanical property changes with aging of Mo-41Re and Mo-47.5Re alloys

The changes in microstructure and mechanical properties of Mo-41Re and Mo-47.5Re alloys were investigated following 1100 h thermal aging at 1098, 1248 and 1398 K. The electrical resistivity, hardness and tensile properties of the alloys were measured both before and after aging, along with the alloy microstructures though investigation by optical and electron microscopy techniques. The Mo-41Re alloy retained a single-phase solid solution microstructure following 1100 h aging at all temperatures, exhibiting no signs of precipitation, despite measurable changes in resistivity and hardness in the 1098 K aged material. Annealing Mo-47.5Re for 1 h at 1773 K resulted in a two-phase αMo + σ structure, with subsequent aging at 1398 K producing a further precipitation of the σ phase along the grain boundaries. This resulted in increases in resistivity, hardness and tensile strength with a corresponding reduction in ductility. Aging Mo-47.5Re at 1098 and 1248 K led to the development of the χ phase along grain boundaries, resulting in decreased resistivity and increased hardness and tensile strength while showing no loss in ductility relative to the as-annealed material.     

Influence of δ phase precipitation on the stress corrosion cracking resistance of alloy 718 in PWR primary water

The negative influence of δ phase on the intergranular stress corrosion cracking (IGSCC) resistance of alloy 718 is commonly taken for granted. In addition, δ phase formed at low temperature (about 1023 K) do not present the same characteristics than the one formed at higher temperatures (from 1173 to 1273 K). The aim of the present study is then to understand how δ phase precipitation could enhance crack initiation in alloy 718, whatever the form of δ phase is. For that purpose, several heat treatments leading to δ phase precipitation were realized on two alloy 718 heats, one sensitive to IGSCC and the second not. Specific slow strain rate tensile tests carried out on thin tensile specimens in simulated PWR primary medium at 633 K conclusively prove that δ phase has no effect on the intrinsic sensitivity to intergranular crack initiation of tested heats.     

BCVEGPY: an event generator for hadronic production of the Bc meson

We have written a Fortran program BCVEGPY, which is an event generator for the hadronic production of the B_c meson through the dominant hard subprocess . To achieve a compact program, we have written the amplitude of the subprocess with the particle helicity technique and made it as symmetric as possible, by decomposing the gluon self couplings and then applying the symmetries. To check the program, various cross sections of the subprocess have been computed numerically and compared with those in the literature. BCVEGPY is written in a PYTHIA-compatible format, thus it is easy to implement in PYTHIA.

Program summary

Title of program: BCVEGPYVersion: 1.0 (September, 2003)Catalogue identifier: ADTJProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTJProgram obtained from: CPC Program Library, Queen's University of Belfast, N. Ireland.Computer: Any computer with FORTRAN 77 compiler. The program has been tested on HP-SC45 Sigma-X workgroups, Linux PCs and Windows PCs with Visual Fortran.Operating systems: UNIX, Linux and Windows.Programming language used: FORTRAN 77.Memory required to execute with typical data: About 2.0 MB.No. of bytes in distributed program, including test data, etc.: 477630No. of lines in distributed program, including test data, etc.: 66461Distribution format: tar gzip fileNature of physical problem: Hadronic production of B_c meson.Method of solution: Improved helicity-approach to the amplitude and symmetries of the amplitude itself have been used to compact the program so as to save cpu as possible as one can. The code with option can generate weighted and un-weighted events. For jet hadronization, an interface to PYTHIA is provided.Restrictions on the complexity of the problem: The hadronic production of the B_c meson in the S-wave states, i.e. pseudo-scalar state () and vector state () are included by the ‘complete calculation’ approach. The hadronic production of B_c meson in P-wave states has not been implemented into the BCVEGPY yet.Typical running time: It depends on which option one chooses to match PYTHIA when generating the B_c events. Typically, if IDWTUP=1, then it takes about 20 hour on a 1.8 GHz Intel P4-processor machine to generate 1000 events; however if IDWTUP=3, to generate 10⁶ events, it takes about 40 minutes only.     

Bragg's Law diffraction simulations for electron backscatter diffraction analysis

In 2006, Angus Wilkinson introduced a cross-correlation-based electron backscatter diffraction (EBSD) texture analysis system capable of measuring lattice rotations and elastic strains to high resolution. A variation of the cross-correlation method is introduced using Bragg's Law-based simulated EBSD patterns as strain free reference patterns that facilitates the use of the cross-correlation method with polycrystalline materials. The lattice state is found by comparing simulated patterns to collected patterns at a number of regions on the pattern using the cross-correlation function and calculating the deformation from the measured shifts of each region. A new pattern can be simulated at the deformed state, and the process can be iterated a number of times to converge on the absolute lattice state. By analyzing an iteratively rotated single crystal silicon sample and recovering the rotation, this method is shown to have an angular resolution of ∼0.04° and an elastic strain resolution of ∼7e−4. As an example of applications, elastic strain and curvature measurements are used to estimate the dislocation density in a single grain of a compressed polycrystalline Mg-based AZ91 alloy.