EFFECTS OF METALLURGICAL PROCESS VARIABLES ON AUSTEMPERED DUCTILE IRONS.

The mechanical properties obtained in austempered ductile iron castings depend on metallurgical process variables, including metal composition and heat treatment conditions. The effects of these variables on both the structure and mechanical properties of austempered ductile irons with predominantly bainitic structures are described in this article, particularly those that influence the integrity and properties of castings supplied to the user. Areas where further work is required are identified. Some practical aspects of the heat treatment of these materials are reviewed, and the potential of near-net shape casting processes is briefly examined.