Properties of ductile cast iron nodularised with multiple calcium–magnesium based master alloy

Abstract

Austempered ductile iron (ADI) is gradually replacing many fabricated and forged steel components in engineering applications. One of its advantages is the combination of good castability, machinability, and mechanical properties with significant savings in cost and weight compared with equivalent steel components. A problem in the production of ADI is the use of expensive and dangerously reactive magnesium as a graphite nodulariser. There is a need to find cheaper, safer, and equally effective substitutes. Results of an investigation of the effectiveness of a multiple calcium–magnesium based master alloy nodulariser and the properties of the ductile iron and ADI produced are reported. Up to 96% nodularity could be obtained using a special Ca–CaC₂–Mg master alloy, compared with 98% using magnesium alone. The mechanical properties were also comparable.