Dual matrix structure (DMS) ductile cast iron: The effect of heat treating variables on the mechanical properties

Abstract

Ductile cast iron with Dual Matrix Structure (DMS) is a new type of cast iron, about which there is very little published information. In this paper the effect of processing type and partial austenitization time on the mechanical properties of Ni-Mo low alloyed ductile cast iron are investigated. In the process of partial austenitization, increasing the heating time above 400 seconds, results in an increase in both the ultimate tensile strength and yield strength. However, impact strength is reduced by an increase in heating time of up to 600 seconds. In the process of incomplete austenitization, better mechanical properties are obtained at higher austenitization temperatures. In the processes of incomplete austenitization, and incomplete ferritization the cooling method after austenitization (i.e., quenching and tempering or austempering) has a pronounced effect on the ductility whereas it has a small effect on the process of partial austenitization. Comparison of the properties of DMS as cast, normalised, quenched- tempered and austempered ductile cast iron show a better ductility for DMS ductile cast iron.