This project aims at starting the development of a general tool for computer simulation of precipitation kinetics and phase transformations in multi-component metallic alloys. Within the MCL, a number of projects are currently running, where precipitation of second phase particles plays a dominant role in controlling the properties of the investigated materials. This project should assist these research projects by providing the possibility of both thermodynamic and kinetic computer simulations.The main focus in the first part of the project lies on a general model for simulating the precipitation kinetics of small second-phase particles. The scientific partners are challenged to develop new approaches for nucleation and growth of particles in the complex multi-component environments of different steel grades including tool steels. So far, no appropriate models are reported in the literature nor commercially available. The second part of the project will include the modelling of the complex behaviour of progressing phase boundaries, where special attention will be drawn to a seamless description of the transition from local equilibrium driven transformations to the limit of partitionless interface movement. An extensive experimental program accompanies the theoretical activities, where the transformation kinetics in model alloys is studied by high-speed quenching dilatometry in order to fill up gaps where experimental data is missing in the literature.