Microstructural Study on Strain Induced Transformation in Austempered Ductile Iron Using Heat Tinting

This work is an experimental study on effect of microstructural change due to Strain Induced Transformation (SIT) of Austempered Ductile Iron (ADI) by heat tinting and corroborates the result with SIT related to machining of ADI. On machining ADI, the microstructure changes rapidly from austenite to martensite due to SIT. The analogy between SIT and machining is addressed in this paper. Evaluation to quantify the likely extent of SIT during machining of grades 900, 1050, 1200 and 1400 via heat tinting of plastically deformed samples has been conducted. Heat tinting causes coloration of the etched specimen, distinguishing each microstructural phase. The initial results appear to indicate the occurrence of SIT on all grades of ADI. SIT can be excessively seen on Grade 1400.