Ductile damage is a consequence of large strains more or less localized. Taking into account damage in constitutive behaviour of metallic materials is necessary to model various engineering problems involved in forming processes (stamping, punching, shearing...). It would lead to accurate predictions introducing microstructural features of materials [1-2]. In the present study, two crystalline plasticity models including damage effects in the framework of scale transition methods are investigated. These models are developed and based on different approaches with direct application to duplex stainless steels. The first approach is a variant of the Berveiller-Zaoui model in which the effect of ductile damage has been introduced. The second one is a generalized Cailletaud model taking into account the ductile damage [3-6]. Because of the microstructural complexity of the chosen materials, some particular developments of the micromechanical approaches are considered. Moreover, continuous damage mechanics is used at grain scale including its effect (or coupling) on plastic or elastic-plastic flow with more or less complex hardenings. The modelling is justified on some previous experimental results in metallic duplex materials [7-8]. The developed models allow then deducing the macroscopic behaviour of the aggregate with damage effects from the grains behaviour.