Hysteresis of Long-Range Ordering in CuAu

1995 ◽  
Vol 398 ◽  
Author(s):  
B. Chalupa ◽  
F. Chmelik ◽  
V. Sima ◽  
B. Sprusil ◽  
M. Spanl ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Cooling Rate ◽  
Long Range ◽  
Long Range Order ◽  
Expected Effect ◽  
Linear Heating ◽  
Glass Forming ◽  
Heating And Cooling ◽  
Small Influence ◽  
Long Range Ordering

ABSTRACTThe effect of heating and cooling on the long-range order transformation in stoichiometric CuAu is investigated by several complementary measuring methods. Measurements of heat flow, resistometry and acoustic emission are done dynamically by linear heating/cooling. It is shown that measuring dynamically yields the expected effect of undercooling, which decreases with decreasing cooling rate. The dependence of undercooling on cooling rate is compared with the concept of continuous cooling for glass forming. A small influence of heating rate on disordering temperature is reported (retro-effect).

Influence of long-range order on tensile properties of Ni3Fe and Ni3Fe—Y2O3 composites

1993 ◽  
Vol 8 (3) ◽  
pp. 430-437 ◽  
Author(s):  
A. Bose ◽  
G. Camus ◽  
R.M. German ◽  
D.J. Duquette ◽  
N.S. Stoloff
Keyword(s):  
Tensile Properties ◽  
Long Range ◽  
Hot Isostatic Pressing ◽  
Long Range Order ◽  
Large Reduction ◽  
Iron Powders ◽  
Disordered Structure ◽  
Isostatic Compaction ◽  
Long Range Ordering ◽  
Hot Isostatic Compaction

Ni3Fe is a compound that exhibits long-range ordering below 500 °C and a disordered structure above this temperature. Thus, Ni3Fe allows study of the effect of ordering on mechanical properties. This paper discusses the tensile properties of Ni3Fe produced via powder metallurgical routes. Some samples subsequently were densified by containerless hot isostatic compaction. Ni3Fe was consolidated with elemental nickel and iron powders that were solid state sintered. Composites of Ni3Fe with 5 vol. % Y2O3 were prepared by presintering cold isostatically pressed rods, followed by containerless hot isostatic pressing. The influence of Y2O3 particles on flow stresses of ordered and disordered Ni3Fe was determined. Ordering of Ni3Fe increased both strength and hardness with a small effect on ductility. For the Ni3Fe–Y2O3 composite, the increase in the strength in both ordered and disordered matrix conditions was accomplished by a large reduction in elongation.

scholarly journals Structural and Energy Characteristics of NiAl Alloys with Deviations from Stoichiometric Composition. Part 2

2020 ◽  
pp. 39-46
Author(s):  
A.I. Potekaev ◽  
A.A. Chaplyginа ◽  
M.D. Starostenkov ◽  
A.A. Klopotov ◽  
V.V. Kulagina
Keyword(s):  
Temperature Dependence ◽  
Long Range ◽  
Structural Phase ◽  
Stoichiometric Composition ◽  
Range Order ◽  
Long Range Order ◽  
Heating And Cooling ◽  
Ordered Phases ◽  
Range Parameter ◽  
The Difference

The analysis of the atomic and phase structure confirmed the difference between the structural-phase states at the heating and cooling stages. Based on the analysis of the influence of the deviation of the atomic composition from the stoichiometric condition of the intermetallic compound during cooling, it is established that the deviation is a significant factor in the area of low-stability pre-transitional structural-phase states before the transformation. The behavior of the long-range parameter temperature dependence curves during the cooling of alloys of non-stoichiometric compositions differs significantly from the behavior of the corresponding alloy curve of a stoichiometric composition alloy. It is shown that in the case of cooling of alloys of non-stoichiometric compositions, a significant supercooling is required to establish a long-range order, and the appearance of ordered phases occurs at significantly lower temperatures. It is found that the temperature dependence curve of the long-range parameter of the Ni45Al55 alloy is significantly lower than the corresponding curve of the Ni55Al45 alloy. This indicates different mechanisms for establishing the long-range order of alloys with non-stoichiometric compositions. It is noted that the deviation of the system composition from the stoichiometric one causes a significant reduction of ordered and disordered regions. This article is a continuation of the work published earlier in the journal Izvestiya AltGU. 2020. №1 (111).

Short-Range to Long-Range Ordering Reactions in a Ni-25Mo-8Cr Alloy

1990 ◽  
Vol 213 ◽  
Author(s):  
Mukul Kumar ◽  
Vijay K. Vasudevan
Keyword(s):  
Long Range ◽  
Transformation Temperature ◽  
Short Range ◽  
Volume Fraction ◽  
Isothermal Holding ◽  
High Volume ◽  
Range Order ◽  
Continuous Heating ◽  
Long Range Order ◽  
Heating And Cooling

ABSTRACTThe transformation from short-range↔long-range order in Haynes® Alloy 242, a nominal Ni-25Mo-8Cr (in wt.%) alloy, during both continuous heating and cooling and isothermal holding at temperatures between 550 and 750°C is reported using dilatometry and microhardness measurements, and optical and transmission electron microscopy The long-range to short-range order transformation temperature was observed to increase with an increase in the degree of prior order. Aging below the transformation temperature led to considerable hardening; this hardening was associated with the formation of a very high volume fraction of Ni2Mo domains/precipitates. On aging at 700°C and below, the hardness initially increases and then levels off, with no evidence of overaging for times to 2000 hours. The role of both short- and long-range order on the transformation temperature, thermal expansion and hardening behavior and the mechanisms of transformation from short-range to long-range order were established and will be discussed.

Crystallization of Supercooled Zr41Ti14Cu12Ni10B23 Melts During Continuous Heating and Cooling

1998 ◽  
Vol 554 ◽  
Author(s):  
Jan Schroers ◽  
Andreas Masuhr ◽  
Ralf Busch ◽  
William L. Johnson
Keyword(s):  
Cooling Rate ◽  
Bulk Sample ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Continuous Heating ◽  
Glass Forming ◽  
Heating And Cooling ◽  
Diffusion Limited ◽  
Surface Nucleation ◽  
The Difference

AbstractThe crystallization behavior of the bulk glass forming Zr41Ti14Cu12Ni10Be23 liquid was studied under different heating and cooling rates. Investigations were performed in high purity graphite crucibles since heterogeneous surface nucleation at the container walls does not effect the crystallization of the bulk sample. A rate of about 1 K/s is sufficient to circumvent crystallization of the melt while cooling from the equilibrium melt. In contrast, upon heating a rate of more than 150 K/s is necessary to avoid crystallization of Zr41Ti14Cu12Ni10Be23 samples. The difference between the critical heating and cooling rate is discussed within classical nucleation theory and diffusion limited crystal growth. The calculated difference of the critical heating and cooling rate can be explained by the fact that nuclei formed during cooling and heating are expose to different growth rates.

CRITICAL STRESS-INDUCED RELAXATION IN RELATION TO LONG-RANGE ORDERING, IN Au3Cu, AND SELF-INDUCED ORDERING, IN AuNi SOLID SOLUTIONS

1987 ◽  
Vol 48 (C8) ◽  
pp. C8-519-C8-524
Author(s):  
G. RENAUD ◽  
M. BELAKHOVSKY ◽  
J. HILLAIRET ◽  
M. WUTTIG ◽  
G. BESSENAY ◽  
...  
Keyword(s):  
Long Range ◽  
Solid Solutions ◽  
Critical Stress ◽  
Long Range Ordering

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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