Ordered intermetallic compounds, 1916-1990

The first ordered intermetallic compound was identified in Russia in 1916, although the concept of long-range order was only clarified by X-ray diffraction, in Sweden, ten years later. Initially, such materials were studied only by chemists trying to understand the basis of combination between metals. Also metallurgists began to be interested in their properties, first magnetic properties and later mechanical properties. The first conference on such compounds, concerned with mechanical properties, was not held until 1960. Now, there are apt to be several conferences devoted to intermetallics in any one year. This paper outlines some of the generalizations which can be made about the variation of the strength and ductility of intermetallic compounds as a function of temperature, with a sideways glance at the behaviour of such alloys when they are plastically annealed (those that are capable of this) and then annealed. The role of varying degrees of long-range ordered is emphasized. More recently, the beneficial effect of combining a 'monolithic' intermetallic phase with another to form an intimate two-phase structure has been established, and this will be exemplified. Finally, future aspects are considered. (author). 67 refs