Abstract
In present paper the effect of austempering conditions and alloying elements on the microstructure, mechanical properties and processing window of Cu and Cu+Ni alloyed austempered ductile irons has been studied. A new concept of “standard” processing window was suggested as an alternative to the well-known “microstructure” processing window. This concept is based on the ability to achieve mechanical properties required by different standards, namely ASTM, ISO and EN. The results obtained show that alloying with Cu+Ni produced ductile grades of ADI, while alloying with Cu grades of higher strength. The standard processing window depends on the austempering parameters and alloying elements, as well as standard used. The ISO and EN standards give a larger standard processing window compared to the ASTM. It was also shown, that from the engineering point of view, determination of a standard processing window gives great advantage compared to the microstructure processing window where special methods and procedures have to be used.

Key words
austempered ductile iron, microstructure, mechanical properties, standard processing window

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