Features of the phase transformation kinetics in ausferritic-carbidic cast irons of the CADI class

The paper provides an analysis of the terminology and structural features of high-strength cast irons of the ADI and CADI classes. A rationale is provided for the term “ausferrite” to describe the metallic matrix formed during isothermal quenching. It is noted that the key distinction of the two-phase (ferrite + austenite) bainite-like structure from martensite is the diffusional mechanism of carbon redistribution, which completely suppresses carbide precipitation. Experimental data confirming the mechanism of deformation-induced martensitic transformation (TRIP effect) in CADI alloys, which provides increased strength and wear resistance, are presented. The main focus is on investigating the kinetics of supercooled austenite decomposition in CADI. The influence of the carbide phase on the heterogeneous nucleation of pearlite and ausferrite has been experimentally established and theoretically substantiated, which is reflected in the need to increase the critical quenching rate compared to ADI in order to suppress diffusional decomposition and form an ausferritic structure. The obtained data can find wide application in industry (mechanical engineering, foundry production) in the manufacture of castings for components operating under impact-abrasive wear conditions.

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