On spinodal decompositionSur la decomposition spinodaleÜber die umsetzung an der spinodalen
Abstract
The stability of a solid solution to all infinitesimal composition fluctuations is considered, taking surface tension and elastic energy into account. It is found that for infinite isotropic solids, free from imperfections the spinodal marks the limit of metastability to such fluctuations only if there is no change in molar volume with composition. Otherwise the elastic energy due to a fluctuation stabilizes the solution and alters the criterion for the limit of metastability. For an unstable solution the kinetics of decomposition are discussed and the expected mean particle size or wavelength of the most rapidly growing fluctuation is derived.
Résumé
L'auteur considère la stabilité d'une solution solide en relation avec des fluctuations infinitésimales de la composition. En tenant compte de la tension superficielle et de l'énergie élastique, on trouve que pour des solides isotropes infinis et exempts d'imperfections, la décomposition spinodale indique la limite de métastabilité aux fluctuations considérées seulement dans le cas où il n'intervient pas de modification du volume molaire avec la composition. Autrement, l'énergie élastique résultant d'une fluctuation stabilise la solution e tmodifie le critère de la limite de métastabilité. L'auteur discute de la cinétique de la décomposition dans le cas d'une solution instable et il en déduit la dimension moyenne de la particule ou de la longueur d'onde associée à la fluctuation la plus rapide.
Zusammenfassung
Die Stabilität einer festen Lösung gegenüber allen infinitesimalen Schwankungen der Zusammensetzung wird betrachtet, dabei werden Oberflächenspannung und elastische Energie mit berücksichtigt. Es wird gezeigt, daβ im unendlichen, isotropen und fehlerfreien Festkörper die Spinodale nur dann die Grenze der Metastabilität bezüglich solchen Schwankungen darstellt, wenn sich das molare Volumen mit der Zusammensetzung nicht ändert. Andernfalls stabilisiert die mit der Schwankung verknüpfte elastische Energie die Lösung und verändert die Bedingungen für die Grenze der Metastabilität. Für eine instabile Lösung wird die Kinetik der Umsetzung diskutiert und die zu erwartende mittlere Teilchengröβe oder die Wellenlänge der am schnellsten wachsenden Schwankung abgeleitet.
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Methods
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Findings
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On leave from the General Electric Research Laboratory Schenectady, New York