RELATIONSHIP OF MICROSTRUCTURAL TRANSFORMATIONS IN AUSTEMPERED NODULAR CAST WITH MICROHARDNESS VALUES.

Austempered ductile iron is the last addition to the group of ductile irons obtained by isothermal improvement of classic ductile iron. Austempered nodular cast iron has improved mechanical properties and a different matrix microstructure compared to known iron-based castings. This type of casting is obtained by isothermal improvement - austempering, whereby the resulting microstructure consists of a mixture of ausferitic (acicular) ferrite and residual, isothermally transformed, carbon-enriched, stable, austenite. Changing the austempering parameters (temperature and time of austenitization and isothermal transformation) affects the obtained ausferite microstructure, and thus the mechanical properties. The most influential parameter that affects the mechanical properties of austempered ductile iron is the isothermal transformation temperature. This paper will present the relationship between microhardness values and microstructural transformations in the material due to the effect of elevated temperatures. [ABSTRACT FROM AUTHOR]