Global Minimization of Lennard-Jones Clusters by a Two-Phase Monotonic Method

2003 ◽  
pp. 221-240
Author(s):  
M. Locatelli ◽  
F. Schoen
Keyword(s):  
Global Minimization ◽  
Two Phase ◽  
Lennard Jones

Performance of the shift method of global minimization in searches for optimum structures of clusters of Lennard-Jones atoms

1992 ◽  
Vol 96 (11) ◽  
pp. 4337-4341 ◽  
Author(s):  
Jaroslaw Pillardy ◽  
Krzysztof A. Olszewski ◽  
Lucjan Piela
Keyword(s):  
Global Minimization ◽  
Shift Method ◽  
Lennard Jones

Elastic Parameters of Various Rafted Structures of Model Ni-Base Alloys

2011 ◽  
Vol 465 ◽  
pp. 85-88
Author(s):  
Jiří Buršík
Keyword(s):  
Applied Stress ◽  
Base Alloy ◽  
Lattice Misfit ◽  
Elastic Parameters ◽  
Two Phase ◽  
Lennard Jones ◽  
Pair Potentials ◽  
Strained Crystal ◽  
Molecular Dynamics Calculations ◽  
Coordination Spheres

Two-phase microstructure of ordered cube-shaped precipitates in the disordered matrix is characteristic of Ni-base superalloys. This microstructure degrades under the applied stress: depending on the stress direction, lattice misfit and elastic parameters of both constituent phases, the precipitates coalesce and change their overall shape. Various atomic configurations were modeled in this work representing various morphologies of precipitates developed under applied stress. A model Ni-base alloy containing six alloying elements typical of advanced Ni-based superalloys was used. Generated configurations were further subject to study of elastic parameters by means of computer straining experiments. Relaxation of atomic positions in the strained crystal blocks was implemented using molecular dynamics calculations with phenomenological Lennard-Jones pair potentials and interactions involving three coordination spheres. Changes of elastic parameters due to varying precipitates morphology are discussed.

Effect of Ordering on the Elastic Parameters of Multicomponent Ni-Based Systems

2005 ◽  
Vol 482 ◽  
pp. 147-150 ◽  
Author(s):  
Jiří Buršík
Keyword(s):  
Disordered Systems ◽  
Elevated Temperatures ◽  
High Symmetry ◽  
Uniaxial Deformation ◽  
Elastic Parameters ◽  
Two Phase ◽  
Cubic Lattice ◽  
Lennard Jones ◽  
Pair Potentials ◽  
Degree Of Order

Ordering in Ni-based superalloys is the crucial process controlling the development of the characteristic two-phase microstructure and subsequently the mechanical properties. Disordered systems containing up to six alloying elements typical of advanced Ni-based superalloys were modelled in this work. Their ordering at elevated temperatures was simulated using a Monte Carlo approach with phenomenological Lennard-Jones pair potentials. Selected atomic configurations differing in the degree of order were subject to further studies of elastic parameters. Hydrostatic deformation and uniaxial deformation along high symmetry directions of model crystals were simulated. Molecular dynamics was used to relax local atomic positions in deformed crystals. Changes of elastic parameters due to ordering in face centred cubic lattice are discussed.

Brittle behavior of a two-phase Lennard-Jones solid

1987 ◽  
Vol 21 (5) ◽  
pp. 697-700
Author(s):  
K. Sieradzki ◽  
K. Shukla
Keyword(s):  
Two Phase ◽  
Brittle Behavior ◽  
Lennard Jones

Effect of Shock Loading on the Microstructure of Uniloy 326

1974 ◽  
Vol 32 ◽  
pp. 504-505
Author(s):  
K. P. Staudhammer ◽  
L. E. Murr
Keyword(s):  
Grain Size ◽  
Shock Loading ◽  
Current Investigation ◽  
Two Phase ◽  
05 C ◽  
Shock Deformation ◽  
Heat Treated

The effect of shock loading on a variety of steels has been reviewed recently by Leslie. It is generally observed that significant changes in microstructure and microhardness are produced by explosive shock deformation. While the effect of shock loading on austenitic, ferritic, martensitic, and pearlitic structures has been investigated, there have been no systematic studies of the shock-loading of microduplex structures.In the current investigation, the shock-loading response of millrolled and heat-treated Uniloy 326 (thickness 60 mil) having a residual grain size of 1 to 2μ before shock loading was studied. Uniloy 326 is a two phase (microduplex) alloy consisting of 30% austenite (γ) in a ferrite (α) matrix; with the composition.3% Ti, 1% Mn, .6% Si,.05% C, 6% Ni, 26% Cr, balance Fe.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

Shock consolidation of Ni-Ti alloy powder

1986 ◽  
Vol 44 ◽  
pp. 430-431
Author(s):  
Naresh N. Thadhani ◽  
Thad Vreeland ◽  
Thomas J. Ahrens
Keyword(s):  
Alloy Powder ◽  
Amorphous Material ◽  
Ti Alloy ◽  
Two Phase ◽  
Near Surface ◽  
Optical Micrograph ◽  
Shock Compaction ◽  
Powder Particles ◽  
Ti Powder ◽  
Rapidly Solidified

A spherically-shaped, microcrystalline Ni-Ti alloy powder having fairly nonhomogeneous particle size distribution and chemical composition was consolidated with shock input energy of 316 kJ/kg. In the process of consolidation, shock energy is preferentially input at particle surfaces, resulting in melting of near-surface material and interparticle welding. The Ni-Ti powder particles were 2-60 μm in diameter (Fig. 1). About 30-40% of the powder particles were Ni-65wt% and balance were Ni-45wt%Ti (estimated by EMPA).Upon shock compaction, the two phase Ni-Ti powder particles were bonded together by the interparticle melt which rapidly solidified, usually to amorphous material. Fig. 2 is an optical micrograph (in plane of shock) of the consolidated Ni-Ti alloy powder, showing the particles with different etching contrast.

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