On the stability of periodically antiphased alloys

Abstract

The Sato‐Toth theory generally invoked to explain the formation of periodically antiphased (PAP) alloys implies that PAP structures are to be stable down to 0 K, AuCu being regarded as an exception. Contrary instances are known to exist, namely: AuCu3, Au3Cu, and Cu3Pt, for which the stable state at low temperatures is the ordered L12 structure. The present experimental study shows that Cu3Pd alloy has the same thermodynamical behaviour. The transition “disorder ↔ PAP ↔ order” could therefore be the rule rather than an exception, which contradicts the theory of Sato and Toth.

The structure of ordered Ag3Mg: an ordinary long-period alloy as opposed to periodically antiphased alloys

“…This transition series is now well established for AuCu (Johannson & Linde, 1936), AuCu 3 (Pianelli, 1959), Au3Cu (Gratias, Condat & Fayard, 1972), CuaPt (Ogawa, Iwasaki & Terada, 1973) and CuaPd (Guymont & Gratias, 1976). The current literature does not make a clear distinction between such PAP structures and what we shall call 'ordinary' long-period structures.…”

“…Hence, if this latter phase is in equilibrium, it can be stated that HpA P > nor d (Guymont & Gratias, 1976).…”

Etude des phases ordonnées à longue période irrationelle. Les alliages AuCu II et AuCu–Zn

“…Cependant, les images obtenues fi l'aide d'un diaphragme d'objectif englobant les taches APP montrent des franges floues et sinueuses rappelant une paroi fluctuante de type Jehanno (Guymont & Gratias, 1978) comme celles obtenues sur CuaPd II (Guymont & Gratias, 1976). L'int6r& d'un examen en haute r6solution est 6vident.…”

Spinodal ordering beyond the lifshitz point in Cu3Pd observed by high voltage electron microscopy

“…F"Ck) = I Ws 'sCk) + '0 (7) s where the w s are effective interaction. parameters, all h-independent terms having been collected into + o'…”