Effect of heat treatment on the damping capacity of austempered ductile cast iron

We investigated the effects of austempering and subzero treatment on the damping capacity in austempered ductile cast iron. The damping capacity of austempered ductile cast iron was rapidly increased by the austempering treatment, although it was not affected by the austempering temperature or time. After subjecting the austempered ductile cast iron to subzero treatment, the austenite was transformed into martensite, and the volume fraction of the martensite increased as the subzero treatment temperature decreased. The subzero treatment sharply increased the damping capacity of the austempered ductile cast iron. However, the damping capacity gradually increased as the subzero treatment temperature decreased. By increasing the subzero treatment time, the damping capacity rapidly increased until the subzero treatment time reached 30 min, after which it increased gradually. By increasing the volume fraction of the martensite, the damping capacity was rapidly increased until the volume fraction was 5%, beyond which it increased gradually.