โ Scribed by N.S Stoloff; T.L Johnston
No coin nor oath required. For personal study only.
A mechanism is advanced for the reduced fracture stress and ductility of metals tested in a liquid metal environment compared to the corresponding properties in air. It is proposed that if the stress necessary to extend 8 craok is calculated on the basis of the rupture of atomic bonds by tensile stresses at the crack tip one can account for the observed effects. Experimental data. on polycrystalline cadmium wetted by liquid gallium are used to illustmte application of the proposed mechanism. The mere act of coating the walls of 8 cleavage crack with liquid metal does not stabilize the crack even though previous thermodynamic interpretations of the effect of the environment on surface energy suggest otherwise. PROPAGATION DES FISSURES DANS UN ENVIRONNEMENT DE METAL LIQUIDE Les auteurs proposent un mecanisme destine 8 expliquer la chute de la tension de rupture et de la ductilite des metaux essay&s dans un environnement de metal liquide. Cet effet s'explique si la contrainte necessaire 8 l'extension d'une fissure est caloul~ sur la base de la rupture de liaisons atomiques par les contraintes de traction 8 l'extremite de la fissure. L'application du mecanisme propose est illustree per des donnQs experimentales relatives au cadmium polycristdlin mouille par le gallium liquide. Le simple fait d'enduire les parois d'une fissure de clivage par du metal liquide ne stabilise p&s la fissure, contrairement 8 ce que suggeraient des interpretations thermodynamiques anterieures de l'influence de I'environnement sur l'energie superficielle. FORTPFLANZUNG VON RISSEN IN EINER UMGEBUNG VON FLUSSIGEM METALL Zur E&l&rung der Verringerung von Bruchspannung und Duktilit&t van Metallen, wenn man den Prlifversuch in einer Umgebung von fliissigem Metal1 durchfiihrt-verglichen mit den entsprechenden Werten in Luft-wird ein Mechanismus vorgetregen. Legt man der Berechnung der Sparmung, die zur Ausdehnung eines Risses notwendig ist, die Vorstellung zugrunde, de6 durch die Zugspsmmngen an der Spitze des Risses die Bindungen zwischen den Atomen zerrissen werden, so kann man die beobachteten Effekte erkl8ren. Zur Erliiuterung des vorgeschlagenen Mechanismus dienen experimentelle Messungen 8n Cadmium, das mit fliissigem Gallium benetzt ist. BloBes Uberziehen der Wiinde eines Spaltrisses mit fltissigem Metal1 geniigt nicht zur Stabilisierung eines Risses, obwohl friihere thermodynamische Deutungen des Einflusses der Umgebung auf die Oberfl&chenenergie das Getenteil besagen.
๐ SIMILAR VOLUMES
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