Numerous welding processes are used in naval, automotive and aircraft industries for joining structural components. Laser beam welding represents a key technology due to his low heat input and the high degree of process automation. Nonetheless, all welded materials are characterised by a strong change of microstructure in the heat effected and fusion zone. For simulation of residual stress fields the finite element method is the most often simulation tool. Reliable simulations have to take into account the changes in microstructure. Within this work, a viscoplastic material model for welding is presented, accounting for the solid and fluid phase, which is extended later on by a simple kinetic model to model precipitation hardening. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)