Multiphase Ausformed Austempered Ductile Iron

Ductile iron was subjected to a total true strain (φ_t) of 0.3 either by applying φ_t in the austenite region or by apportioning it through applying a true strain of 0.2 in the austenite region before quenching to austempering temperature (T_A) of 375°C, where a true strain of 0.1 is applied (ausforming). Additionally, two types of matrices were produced in the ductile iron, namely ausferritic and ferritic-ausferritic matrices. The ferrite is introduced to the matrix by intercritical annealing after austenitization. Dilatometric measurements as well as microstructure examination showed a fast ausferrite transformation directly after applying φ_A and that the introduction of ferrite to the matrix resulted in a remarkable acceleration of the ausferrite formation. The transformation kinetics, microstructure evolution, hardness and compression properties are studied.