PRODUCTION OF EUTECTIC BODIES BY UNIDIRECTIONAL SOLIDIFICATION

摘要

1382528 Crystal pulling TYCO LABORATORIES INC 30 Oct 1972 [8 Nov 1971] 49860/72 Heading B1S Polyphase crystalline bodies of substantially uniform morphology are formed from eutectic compositions by directional solidification and by establishing a thin film of a eutectic composition on a substantially flat supporting surface which functions as a die by using the edge configurations of the die to determine the shape of the desired body and controlling the temperature of the film so that it has (1) a steep temperature gradient along its depth with the film being hottest at the surface (2) a substantially uniform temperature along its length and breadth and (3) an average temperature approximately equal to the eutectic temperature of the composition, solidifying and pulling a mass of said composition from the cooler side of the film on a crystalline seed at a selected rate and simultaneously supplying an additional quantity of the composition in liquid form to the surface to replace the liquid consumed in producing the crystalline body. The flat die surface is preferably porous i.e. part of a member consisting of a myriad of interconnected open cells. The eutectic compositions may be Al-Al 3 N, Al- CuAl 2 , Pb-Sn, Cd-Zn, Mg-Mg 17 Al 12 , NiSb-InSb, Cu-Cr alloys, nickel-base super alloys, LiFNaCl, or LiF-CaF 2 . The bodies are made by known techniques (EFC process) using a die surface which carries a film of the liquid to be pulled and fed by capillary passages exiting in the die surface. The shown figure relates to a modification of the standard apparatus wherein the die assembly 14A, consists of a disc 16 holding in a bath 4a porous rod 18A e.g. of alumina sponge, containing many open cells which function as capillaries. The film 32, is formed on flat surface 20 and the body drawn from the film by seed 26. The seed may undergo rotation as it is being withdrawn to give twisted bodies. Example III describes such a product. The bodies in structure are of indefinite length and have a microstructure in which one phase consists of parallel plates or rods disposed in a matrix of another phase in a regular manner.