There are many challenges in producing components by additive manufacturing (AM). One of them is to keep the residual stresses and deformations to a minimum. Another one is to achieve the desired material properties in the final component. Residual stresses in AM components are a well-known problem and it causes distortion of the samples when removing them from the build plate, as well as acting detrimental with regard to fatigue. This presentation will focus on the residual stresses and is a part of the EC funded project FatSAM [1]. A simulation model can be of great assistance for mitigating the negative effects of the manufacturing process. One key component in the modelling process is to describe the materials response correctly. A mechanism-based flow stress model will be used in this work. It is a physically founded constitutive model based on the evolution of immobile dislocation density. This model is capable of describing plastic flow of the alloy of interest in a wide range of temperatures, strain and strain rates by including the dominant deformation mechanisms like dislocation pile-up, dislocation glide, thermally activated dislocation climb, globularization, etc. The phenomena of flow softening and stress relaxation can also be reproduced with this model. This type of constitutive model also has a natural handshake with microstructure models such as phase change models and morphology models. The capability of the constitutive model will be demonstrated by application in thermo-mechanical finite element simulations of the AM process. Results such as residual stresses and deformations will be compared with measurements to determine the validity of the model. The residual stresses are attained from synchrotron X-ray diffraction measurements.