ABSTRACT
The last few decades have seen metals enter new fields of expansion as the result of nuclear energy, guided missiles, jet engines and space technology. These usages involving extreme temperatures, radiation, high pressures and speed have led to the creation of new techniques in metal extraction and fabrication. Improvements in properties of the older metals have not served to satisfy the exacting demands imposed by these new environments, and metallurgists have had to turn to metals which were formerly considered too rare or too reactive. The increase in research into their extraction and refining has resulted in the development of such radically new techniques as ion exchange, solvent extraction, zone refining, electrode-arc melting, and high-pressure leaching. In Great Britain, the development and production during and after the last war of a series of alloys based on the nickel chromium system has contributed significantly to the progress made with such engines.
