Hydrogen Embrittlement of FeAl and Fe3Al

1990 ◽  
Vol 213 ◽  
Author(s):  
M. Shea ◽  
A. Castagna ◽  
N. S. Stoloff
Keyword(s):  
Hydrogen Embrittlement ◽  
Strain Rate ◽  
Long Range ◽  
Mixed Mode ◽  
Al Alloys ◽  
Range Order ◽  
Iron Aluminides ◽  
Long Range Order ◽  
Intergranular Cracking

ABSTRACTThis paper deals with the role of charging conditions and strain rate on the embrittlement of several Fe.Al and Fe3Al alloys. Fracture paths are transgranular or mixed mode in both air and after precharging of the iron aluminides, unlike the intergranular cracking typical of Ll2 superlattices exposed to hydrogen. The fractographic observations are consistent with a decohesion mechanism. The role of long range order in transport of hydrogen will be discussed.

scholarly journals Engineering Long-Range Order in Supramolecular Assemblies on Surfaces: The Paramount Role of Internal Double Bonds in Discrete Long-Chain Naphthalenediimides

2020 ◽  
Vol 142 (8) ◽  
pp. 4070-4078 ◽  
Author(s):  
José Augusto Berrocal ◽  
G. Henrieke Heideman ◽  
Bas F. M. de Waal ◽  
Mihaela Enache ◽  
Remco W. A. Havenith ◽  
...  
Keyword(s):  
Long Range ◽  
Supramolecular Assemblies ◽  
Range Order ◽  
Long Range Order ◽  
Double Bonds ◽  
Long Chain

The Suitability Of The Lattice Fringe Imaging Technique For Measuring Spatial Variation In Degree Of Long-Range Order In Fe-Al Alloys

1977 ◽  
Vol 35 ◽  
pp. 184-185
Author(s):  
Samuel M. Allen
Keyword(s):  
Long Range ◽  
Imaging Technique ◽  
Superlattice Reflection ◽  
Dynamical Theory ◽  
Al Alloys ◽  
Range Order ◽  
Long Range Order ◽  
Lattice Fringe ◽  
Feal Phase ◽  
Simulated Images

A computer simulation of lattice fringe imaging of ordered Fe-Al alloys has been carried out, using the multiple beam dynamical theory of electron diffraction as formulated by Sinclair et al. for CU3AU (1). The object of the study was to determine the suitability of the lattice fringe imaging technique for studying spatial variations in long-range order parameter in singlephase ordered specimens.In the interest of simplicity, the results of simulations in which eight beams were excited in the (200) systematic row for an imperfectly B2-ordered alloy of composition Fe-25% aluminum will be presented. (The prototype crystal structure for the FeAl phase is CsCl.) Simulated images were obtained by combining the direct beam with the (100) superlattice reflection, for the case in which Bragg's Law was satisfied for the (100) reflection, and with both beams equidistant from the optic axis of the microscope.Image intensities as a function of distance parallel to [200] were computed for different specimen thicknesses and long-range order parameters.

Superfluidity and Superconductivity

2018 ◽  
Author(s):  
Norman J. Morgenstern Horing
Keyword(s):  
Magnetic Field ◽  
Wave Function ◽  
Wave Packet ◽  
Long Range ◽  
Cooper Pair ◽  
Bose Condensation ◽  
Range Order ◽  
Condensed State ◽  
Long Range Order ◽  
Coherent Wave

Chapter 13 addresses Bose condensation in superfluids (and superconductors), which involves the field operator ψ‎ having a c-number component (<ψ(x,t)>≠0), challenging number conservation. The nonlinear Gross-Pitaevskii equation is derived for this condensate wave function<ψ>=ψ−ψ˜, facilitating identification of the coherence length and the core region of vortex motion. The noncondensate Green’s function G˜1(1,1′)=−i<(ψ˜(1)ψ˜+(1′))+> and the nonvanishing anomalous correlation function F˜∗(2,1′)=−i<(ψ˜+(2)ψ˜+(1′))+> describe the dynamics and elementary excitations of the non-condensate states and are discussed in conjunction with Landau’s criterion for viscosity. Associated concepts of off-diagonal long-range order and the interpretation of <ψ> as a superfluid order parameter are also introduced. Anderson’s Bose-condensed state, as a phase-coherent wave packet superposition of number states, resolves issues of number conservation. Superconductivity involves bound Cooper pairs of electrons capable of Bose condensation and superfluid behavior. Correspondingly, the two-particle Green’s function has a term involving a product of anomalous bound-Cooper-pair condensate wave functions of the type F(1,2)=−i<(ψ(1)ψ(2))+>≠0, such that G2(1,2;1′,2′)=F(1,2)F+(1′,2′)+G˜2(1,2;1′,2′). Here, G˜2 describes the dynamics/excitations of the non-superfluid-condensate states, while nonvanishing F,F+ represent a phase-coherent wave packet superposition of Cooper-pair number states and off-diagonal long range order. Employing this form of G2 in the G1-equation couples the condensed state with the non-condensate excitations. Taken jointly with the dynamical equation for F(1,2), this leads to the Gorkov equations, encompassing the Bardeen–Cooper–Schrieffer (BCS) energy gap, critical temperature, and Bogoliubov-de Gennes eigenfunction Bogoliubons. Superconductor thermodynamics and critical magnetic field are discussed. For a weak magnetic field, the Gorkov-equations lead to Ginzburg–Landau theory and a nonlinear Schrödinger-like equation for the pair wave function and the associated supercurrent, along with identification of the Cooper pair density. Furthermore, Chapter 13 addresses the apparent lack of gauge invariance of London theory with an elegant variational analysis involving re-gauging the potentials, yielding a manifestly gauge invariant generalization of the London equation. Consistency with the equation of continuity implies the existence of Anderson’s acoustic normal mode, which is supplanted by the plasmon for Coulomb interaction. Type II superconductors and the penetration (and interaction) of quantized magnetic flux lines are also discussed. Finally, Chapter 13 addresses Josephson tunneling between superconductors.

Time-Resolved, Laser-Induced Phase Transformation in Aluminum

1984 ◽  
Vol 35 ◽  
Author(s):  
S. Williamson ◽  
G. Mourou ◽  
J.C.M. Li
Keyword(s):  
Point Defect ◽  
Long Range ◽  
Rapid Heating ◽  
Range Order ◽  
Nucleation Theory ◽  
Long Range Order ◽  
Time Resolved ◽  
Aluminum Films ◽  
Thin Aluminum ◽  
Initial Nucleus

ABSTRACTThe technique of picosecond electron diffraction is used to time resolve the laser-induced melting of thin aluminum films. It is observed that under rapid heating conditions, the long range order of the lattice subsists for lattice temperatures well above the equilibrium point, indicative of superheating. This superheating can be verified by directly measuring the lattice temperature. The collapse time of the long range order is measured and found to vary from 20 ps to several nanoseconds according to the degree of superheating. Two interpretations of the delayed melting are offered, based on the conventional nucleation and point defect theories. While the nucleation theory provides an initial nucleus size and concentration for melting to occur, the point defect theory offers a possible explanation for how the nuclei are originally formed.

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