A Thermodynamic 3D Model for the Simulation of Diffusion‐Controlled Alloying Processes in Heterogeneous Material Structures

A numerical model is introduced in which the thermodynamic diffusion approach resulting from irreversible thermodynamics is consistently applied. Unlike Fick's approach that relies on concentration gradients, the thermodynamic approach employs the actual driving force for diffusion, which is the gradient of a component's thermodynamic activity. Utilizing CalPhaD programs to extract component activities from thermodynamic databases, a numerical calculation method was developed and implemented using CUDA C++, in order to apply the thermodynamic model. The model's effectiveness was evaluated using the binary aluminum‐iron system, starting from pure metal diffusion couples and simulating interdiffusion until complete mixing under varying conditions. It is shown that the thermodynamic model accurately predicts phase changes and the formation of intermetallic phases using only a singular global diffusion coefficient valid for both components and all phases. The model's application to complex geometries is demonstrated on the alloying of an interpenetrating composite.