The constant reduction of production costs and the development of materials during recent years are favoured the development of Austempered Ductile Iron (ADI) because of favourable combination of technological and structural properties. The process of forging on ADI makes it possible to obtain final parts with good dimensions. Moreover, Austempered Ductile Iron has a remarkable workability. ADI has many advantages, including the possibility of modifying and of improving the mechanical characteristics by thermo mechanical treatments while preserving a relatively low production cost, thus competing with many categories of steels. The study presented relates to the influence of the parameters of the thermo mechanical treatments on the proportion of residual austenite allowing modification of the mechanical characteristics of the material and on the evaluation of the residual stresses.