(Parameterised potentials calibrated using DFT, for greater accuracy.) Uses the best-available MM3 potentials, falling back onto UFF (Universal Force Field) where necessary.Hybrid least-squares cycle added to provide greater precision in the closing stages of refinement.Monte Carlo technique allows relaxation of structures far from equilibrium - e.g., crude, hand-drawn structures with excessive bond lengths and distorted bond angles!.Smart selection of potentials, based on bonding environment: requires no additional user input.Force field approach, using parameterised potentials (MM3 where possible, otherwise UFF).Provides energy minimization for new H positions, leaving the remainder of the molecule unchanged - hence ideal for adding H atoms to an "X-Ray Structure". Option to relax a selected group of atoms, independently of the rest of the structure: ideal for working with extended, macro-molecular structures.Use the Relax Molecule command to optimize your molecule, via a sophisticated Monte-Carlo algorithm that takes into account the existing bonding, and auto-identifies carbon hydridisation.Selection menu provides commands to duplicate, detach, move or edit any group of selected atoms.Atom Picker palette lets you change the atom type associate with the Add Atom tool.Shift-click to simultaneously add an atom and a bond.
Click with the Add Atom tool to define the positions of new atoms.Pollock, Metallurgical and Material Transactions A, 40 (2009) 1588-1603.ĭ.M. Denis, Journal de Physique IV, 6 (1996) 9. ThermoTech Ltd.: TTNi6, TT Ni-based Superalloys Database, Surrey Technology Center, Guildford, 2003. Sundman B.: ThermoCalc User Guide, KTH Stockholm, 1993. Carpenter, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 239 (1985) 536-544. Von Dreele: General Structure Analysis System (GSAS), Los Alamos National Laboratory Report LAUR 86-748 (1994). Knight: ISIS Spallation Neutron & Muon Source, 1992, p. Preuss, Metallurgical and Materials Transactions A, 38A (2007) 615-627. Wahi, Acta Metallurgica et Materialia, 43 (1995) 507-517. Banerjee, Materials Science and Engineering: A, 528 (2010) 32-36. Voorhees, Journal of Statistical Physics, 38 (1985) 231-252. Christian, The Theory of Transformations in Metals and Alloys, Pergamon, Oxford, 2002. Fecht: Superalloys, TMS, Warrendale, PA, 2000, pp. Lemsky: Assessment of NASA Dual Microstructure Heat Treatment Method Utilizing Ladish SupercoolerTM Cooling Technology, National Aeronautics and Space Administration (NASA), Washington, DC, 2005, p. Reynolds: Superalloys, TMS, Warrendale, PA, 2004, pp. Reed, Materials Science and Engineering A, 259 (1999) 85-97. Thesis, Department of Materials Science and Metallurgy, University of Cambridge, 2009 Connor, TMS Superalloys, Seven Springs, Pennsylvania, 2008. Reed, The Superalloys: Fundamentals and Applications, Cambridge University Press, Cambridge, 2006. The results obtained indicate that conventional methods of measuring lattice misfit will be dominated by the γ′ distribution with the highest volume fraction, and may therefore obscure subtle changes in the γ′ distributions with lower a volume fraction. Simulated diffraction patterns were used to investigate the influence of volume fraction, particle size, and lattice parameter of individual γ′ distributions on the measured lattice misfit. However, for the faster, 100 K min −1, cooling rate, whilst the secondary γ′ remained unchanged, the tertiary γ′ showed significant coarsening.
Microstructural observations validated this result for samples cooled at 1 K min −1. Irrespective of cooling rate, the lattice misfit remained unchanged at approximately 0.1 pct throughout the aging cycle, indicating the microstructure remained stable. Samples were subjected to a super-solvus heat treatment followed by either a 100 or a 1 K min −1 cooling rate prior to aging. The evolution of lattice misfit in the polycrystalline nickel-base superalloy, RR1000, has been investigated using high resolution neutron diffraction at interrupted time intervals during an aging heat treatment.
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