Method of alloying reactive components

Abstract

Metal seeds for forming single-crystal shape-memory alloys (SMAs) may be fabricated with high reliability and control by alloying thin films of material together. In particular, described herein are methods of forming AlCuNi SMAs by first producing high-quality seeds (ingots) of copper, aluminum, and nickel to produce for pulling single crystal shape memory alloys, in particular superelastic or hyperelastic alloys. The method is applicable to a wide range of alloys in which one or more of the components are reactive. The method is an improvement upon traditional methods such as mixing and melting pellets. In this improved method, a reactive layer (e.g., aluminum) is provided in thin flat layers between layers of other materials (e.g., copper and layers of nickel). When the stacked layers are vacuum heated in a crucible to the melting temperature of the reactive layer, it becomes reactive and chemically bonds to the other layers, and may form eutectics that, as the temperature is further increased, melt homogeneously and congruently at temperatures below the melting temperatures of copper and nickel. Oxidation and evaporation are greatly reduced compared to other methods of alloying, and loss of material from turbulence is minimized.