We propose to investigate the deformation states of two different grades of austempered ductile irons (ADIs) pre-strained through tensile tests. ADIs microstructures consist of two phases, high vol. fractions of ferrite (dep. on the grade) and metastable austenite with high carbon content. There is little literature on the microplasticity of the dual phase structures in ADIs. In the softer ADI 800 there is about 30% v/v of austenite that increases the ductility, and the structure is coarser than the stronger ADI 1050 with less austenite. The comparison of the two different grades of ADIs is also important to understand the contribution of the two phases to the macroscopic deformation of ADIs. Through ND, wide volumes of the inner strained materials can be analysed, and microplasticity mechanisms in the two phases can be revealed and correlated to the macroscopic flow behaviours of ADIs.