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

1990 ◽  
Vol 213 ◽  
Author(s):  
Mukul Kumar ◽  
Vijay K. Vasudevan

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.

1977 ◽  
Vol 38 (C7) ◽  
pp. C7-202-C7-206 ◽  
Author(s):  
R. MORET ◽  
M. HUBER ◽  
R. COMÈS

1997 ◽  
Vol 12 (8) ◽  
pp. 2117-2126 ◽  
Author(s):  
Hyun M. Jang ◽  
Su-Chan Kim

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.


2019 ◽  
Vol 123 (29) ◽  
pp. 17933-17942
Author(s):  
Anatoly Koshelev ◽  
Elena Zvereva ◽  
Larisa Shvanskaya ◽  
Olga Volkova ◽  
Mahmoud Abdel-Hafiez ◽  
...  

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

1985 ◽  
Vol 106 ◽  
pp. 551-558
Author(s):  
Philip E. Seiden

Most approaches to explaining the long-range order of the spiral arms in galaxies assume that it is induced by the long-range gravitational interaction. However, it is well-known in many fields of physics that long-range order may be induced by short-range interactions. A typical example is magnetism, where the exchange interaction between magnetic spins has a range of only 10 ångströms, yet a bar magnet can be made as large as one likes. Stochastic self-propagating star formation (SSPSF) starts from the point of view of a short-range interaction and examines the spiral structure arising from it (Seiden and Gerola 1982). We assume that the energetic processes of massive stars, stellar winds, ionization-front shocks and supernova shocks, in an OB association or open cluster can induce the creation of a new molecular cloud from cold interstellar atomic hydrogen. In turn this new molecular cloud will begin to form stars that will allow the process to repeat, creating a chain reaction. The differential rotation existing in a spiral galaxy will stretch the aggregation of recently created stars into spiral features.


2001 ◽  
Vol 13 (1) ◽  
pp. 96-102 ◽  
Author(s):  
E. García-González ◽  
M. Arribas ◽  
J. M. González-Calbet

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

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