�ber Widerstandslegierungen

Thomas, Hans

doi:10.1007/bf01333398

Cited by 128 publications

(35 citation statements)

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“…Early evidence for structural variations within the a-phase region of the Ni-Mo system was provided by the electrical-resistivity measurements made by Thomas,43 who observed that the electrical resistivity of quenched or cold-worked alloys was higher than for slowly cooled alloys. The anomalous behaviour was attributed to a 'K state', some structural or electronic state not yet understood.…”

Section: Short-range Ordermentioning

confidence: 98%

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Physical metallurgy of nickel—molybdenum alloys

Brooks¹,

Spruiell²,

Stansbury³

1984

International Metals Reviews

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The physical metallurgy of Ni -rich Ni-Mo alloys is reviewed. Three ordered intermetallic compounds can form in this system, which leads to some intriguing microstructures and has significant effects on properties. The understanding of the nature of these phases, how they are formed, and the factors responsible for property changes are summarized; areas needing further research are indicated. The phase relations and transformations in alloys containing approximately 20 at. -~oMowith Fe additions are reviewed, as these serve as the basis for some commercial alloys. The structures and properties of the commercial alloys are also reviewed.IMR/133 INTRODUCTIONThe physical metallurgy of Ni-Mo alloys is of interest and importance for several reasons. The phase transformations that occur in them generate spectacular microstructures, the study of which leads to a better understanding of principles important to all alloy systems; these structures significantly affect properties; and some of the compositions serve as bases for commercial alloys. Although there is an extensive literature on Ni-Mo alloys, this is the first review to give a perspective view of the state of understanding of these alloys. The transformationsinvolve short-rangeordered (SRO) and long-range-ordered (LRO) phases, which have been studied extensively using optical and electron microscopy, X-ray diffraction, and other techniques. (For reviews of the physical metallurgy and mechanical behaviour of ordered alloys, see Many of the characteristics of the kinetics and morphology of the transformations are well understood; however, there are areas of controversy and many features are yet to be explained, especially the correlation of structure and properties.

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Section: Short-range Ordermentioning

confidence: 98%

“…1,3, the transformation occurs most rapidly at about 775°C, but is quite sluggish at temperatures below about 550°C (Refs. [41][42][43].…”

Section: A-phase (Nimo)mentioning

confidence: 99%

Physical metallurgy of nickel—molybdenum alloys

Brooks¹,

Spruiell²,

Stansbury³

1984

International Metals Reviews

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“…[10][11][12][13][14] It is sometimes referred to as the K state. 15,16 Khachaturyan and Viehland have assumed that this compositionally heterogeneous state leads to a cubic ͑C͒ → tetragonal ͑T͒ displacive transformation that brings the structure closer to an equilibrium fcc-based L1 2 ordered phase. This also explains that giant extrinsic magnetostriction and elastic softening are then caused by the macroscopic strain generated by a magnetic field-induced displacive transformation or a stress-induced reorientation of tetragonal phase nanotwins.…”

Section: Introductionmentioning

confidence: 99%

NanodispersedDO3-phase nanostructures observed in magnetostrictive Fe–19% Ga Galfenol alloys

et al. 2008

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Few nanometer large ͑Ͻ2 nm͒ inclusions of DO 3 -phase structure have been identified in the A2 matrix of highly magnetostrictive Fe-19% Ga alloys by high-resolution transmission electron microscopy ͑HRTEM͒. In addition, we have found that these nanostructures include a high density of ͕100͖ line defects with a Burgers vector of a bcc 2 ͗100͘. This dispersion of DO 3 -phase nanostructures formed within the main A2 matrix and the lifting of their coherency by defects are consistent with a recent theory for the structure and properties of magnetostrictive Fe-Ga and Fe-Al alloys ͓A.

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“…We obtain ments can be described by the same semi-empirical eq. (1) and (2). Since the analysis gives identical values for the reaction orders a and 0 it can be conclud-and Q prove the assumption that in both alloys sro ed that short range-ordering and the formation of the formation is not only controled by the annihilation K-state are identical or at least very similar processes.…”

Section: Isothermal Experimentsmentioning

confidence: 64%

THE INFLUENCE OF QUENCHED-IN AND THERMAL VACANCIES UPON SHORT-RANGE-ORDER FORMATION IN A Ni 11.4 AT % Cr ALLOY

1977

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RBsumC. -Les anomalies de rksistivitk apr&s le traitement thermique d'alliages dont un composant au moins est un mktal de transition, ont Ct C traitkes par differents auteurs deja. L'accroissement anormal de la courbe de rksistivitk en fonction de la temperature a ktk attribuk B la formation de l'Ctat appele ct K )) des alliages.Dans le present exposk, l'alliage Ni 11,4 % at Cr a Ctk rkktudik. Les formes des courbes isochrones et isothermes mesurees sont t r b semblables a celles trouvees pour un alliage Au 15 % at Ag. C'est la raison pour laquelle l'analyse basee sur la diffusion de lacunes et la formation d'ordre a courte distance, telle que dkveloppke pour l'alliage Au-Ag, a ktk appliquke aussi aux experiences NiCr. Ici aussi les valeurs autoconsistantes trouvees pour les energies de formation et de..migration-de lacunes ainsi que l'energie d'activation d'autodiffusion sont en accord avec les valeurs dkja connues.Abstract. -Different authors have reported upon resistivity anormalities after thermal treatment of alloys with at least one component being a transition metal. The abnormal increase in the resistivity vs. temperature curve was attributed to the formation of the so-called ( c K ))-state of the alloys.In the present contribution the alloy Ni 11.4 at % Cr has been re-investigated. The shapes of the measured isochronal and isothermal curves are very similar to those found on an Au 15 at % Ag alloy. For this reason the analysis based on vacancy diffusion and short-range-order formation, as developed for the Au-Ag-alloy has been applied also to the NiCr experiments. Also here selfconsistent values for the enthalpies of formation and migration of vacancies as well as the activation enthalpy of selfdiffusion could be determined in good agreement to the values found in literature.1. Introduction. -In the early fifties, detailed investigations were made on the electrical resistivity of alloys with at least one component being a transition metal [l-51.For instance Thomas [2] reports about three anormalities in resistivity measurements in NiCr alloys :1) The resistivity vs. temperature curve is not linear, but t( S ))-shaped.2) After quenching from high temperatures the resistivity of a sample increases during an annealing treatment at lower temperature.3) In contrast to the behaviour of pure metals and many alloys the resistivity of the samples can be decreased by cold deformation.The author assumed that these anormalities were caused by the so-called <( K-state )) which should arise in these alloys at low temperatures (l). However, no detailed information has been provided as to what this state should be microscopically. Although it was assumed that diffusion should control the formation of this state, ordering phenomena were excluded because ordering was assumed to always decrease the electrical resistivity as it is found for long-range-

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�ber Widerstandslegierungen

Cited by 128 publications

References 0 publications

Physical metallurgy of nickel—molybdenum alloys

Physical metallurgy of nickel—molybdenum alloys

NanodispersedDO3-phase nanostructures observed in magnetostrictive Fe–19% Ga Galfenol alloys

THE INFLUENCE OF QUENCHED-IN AND THERMAL VACANCIES UPON SHORT-RANGE-ORDER FORMATION IN A Ni 11.4 AT % Cr ALLOY

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