Method of dimensionally stabilizing interface between dissimilar metals

Abstract

Method of dimensionally stabilizing the interface between metal parts of differing thermal expansion characteristics (TEC), regardless of temperature variations under normal designed use of such parts, comprising: (a) hot extruding a mixture of ceramic fibers (i.e., Si.sub.3 N.sub.4, SiC, Al.sub.2 O.sub.3) and a powder of the metal having the higher TEC (i.e., Al, Ti, Mg) while aligning the fibers generally along the direction of extrusion, to form an insert; (b) shaping the insert to align its fibers generally in at least one direction of anticipated thermal growth that may interfere with the interface; (c) casting the insert in place within a first part compound of the higher TEC metal and with the insert's fibers (i) oriented as above, and (ii) preheated to a temperature no greater than 35-45% of the temperature of the molten light metal; and (d) bringing together the first metal part with a second part of lower TEC metal (i.e., Fe or steel) to form the interface. The insert may be located in a mold in a manner to be totally enveloped by the molten light metal with the insert having a surface spaced a uniform, predetermined distance from the exterior of the cast light metal part, or the insert may be located to expose a surface thereof upon completion of the casting.