Short-range order to long-range order transition in a Cu-Ti alloy

1993 ◽  
Vol 51 ◽  
pp. 1180-1181
Author(s):  
J.S. Lee ◽  
R.W. Carpenter ◽  
H. Lim ◽  
W.K. Choo
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Long Range ◽  
Electron Diffraction Pattern ◽  
Short Range ◽  
Short Range Order ◽  
Range Order ◽  
Ti Alloy ◽  
Long Range Order ◽  
Ti Alloys

Cu-Ti alloys have received attention due to their excellent age-hardenability. The age hardening phenomenon of Cu-Ti alloys is closely related to the early stage transformation involving short-range order (SRO), spinodal decomposition, and long-range order (LRO). Despite many researches, the transition from SRO to LRO state in this alloy system is still not understood. Woychik et al. have found {1 1/2 0} SRO reflections in an electron diffraction pattern of an as-rapidly solidified (RS) Cu-15at.%Ti alloy (All indices are referred with respect to the fcc structure in this paper.). with aging, the SRO reflections were replaced by the 4/5{l 1/2 0} LRO (Dla) reflections. Recently, Yoo found the {1/2 1/2 0} spots as well as the {1 1/2 0} spots in an electron diffraction pattern of an as-RS Cu-15at.%Ti alloy. This result may show that some other metastable phases can be present before the formation of the LRO phase. In the present paper, the initial stages of ordering process will be described.

Pb()O3-type Perovskites: Part I. Pair-correlation Theory of Order-disorder Phase Transition

1997 ◽  
Vol 12 (8) ◽  
pp. 2117-2126 ◽  
Author(s):  
Hyun M. Jang ◽  
Su-Chan Kim
Keyword(s):  
Long Range ◽  
Order Parameter ◽  
Short Range ◽  
Short Range Order ◽  
Pair Correlation ◽  
Range Order ◽  
Statistical Thermodynamic ◽  
Range Order Parameter ◽  
Long Range Order ◽  
Short Range Order Parameter

The limitation of the long-range order parameter and the necessity of the short-range order parameter for the thermodynamic description of Pb()O3-type perovskites are discussed. Based on the discussion, a statistical thermodynamic model that takes into account the configuration of the neighboring B-site ions (B′ and B″ cations) was developed. A pair-correlation approximation was used in the calculation of the configurational entropy and the long-range coulombic interaction energy between the nearest B-site ions. The theoretical calculations using Pb(Sc1/2Ta1/2)O3 (PST) and Pb(Sc1/2Nb1/2)O3 (PSN) systems indicate that the short-range order parameter persists over a wide range of temperatures examined (0–1800 K) and that there possibly occur consecutive long-range order-disorder transitions in the configuration of B-site cations. The possibility of the existence of short-range ordering above the long-range order-disorder transition temperature was also examined using the annealed PSN specimen as a typical example of Pb()O3-type perovskites.

Short range order and its transformation to long range order in Ni4Mo

1998 ◽  
Vol 46 (3) ◽  
pp. 881-892 ◽  
Author(s):  
Satoshi Hata ◽  
Syo Matsumura ◽  
Noriyuki Kuwano ◽  
Kensuke Oki
Keyword(s):  
Long Range ◽  
Short Range ◽  
Short Range Order ◽  
Range Order ◽  
Long Range Order

Short‐Range Order Coexisting with Long‐Range Order in Cu3Au

1956 ◽  
Vol 27 (3) ◽  
pp. 203-206 ◽  
Author(s):  
B. W. Roberts ◽  
G. H. Vineyard
Keyword(s):  
Long Range ◽  
Short Range ◽  
Short Range Order ◽  
Range Order ◽  
Long Range Order

Order-disorder in 1:1 type clay minerals by solid-state 27Al and 29Si magic-angle-spinning NMR spectroscopy

Clay Minerals ◽  
1985 ◽  
Vol 20 (3) ◽  
pp. 327-334 ◽  
Author(s):  
S. Komarneni ◽  
C. A. Fyfe ◽  
G. J. Kennedy
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Long Range ◽  
Short Range ◽  
Short Range Order ◽  
Magic Angle Spinning ◽  
Range Order ◽  
Magic Angle ◽  
Long Range Order ◽  
Tetrahedral Coordination ◽  
Angle Spinning

AbstractThe applicability of 27Al and 29Si magic-angle-spinning nuclear magnetic resonance (MASNMR) spectroscopy to the investigation of order-disorder in 1 : 1 dioctahedral layer-silicates was tested. 27Al and 29Si MASNMR showed the existence of short-range order in all these systems while XRD showed different degrees of long-range order-disorder. Spectra obtained on kaolinite and metakaolin clearly showed the transformation of some octahedral Al in kaolinite to tetrahedral coordination in metakaolin and also showed short-range Al and Si disorder in the latter. This suggests that structural re-arrangement on thermal treatment can be monitored by this technique. These results further suggest that MASNMR can detect short-range order, which is complimentary to the information that XRD provides regarding long-range order.

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