1-8. Applications of Computational Thermodynamics to Additive Manufacturing

Andreas Markström, Shan Jin, Adam Hope, Paul Mason, Johan Bratberg
Thermo-Calc Software AB, Råsundavägen 18, SE-169 67 Solna, Sweden

Abstract: Interest in Additive Manufacturing has increased dramatically in recent years due to its broad range of benefits such as rapid prototyping and free form design. However, the current understanding of materials processing and behaviour is insufficient in this rapidly evolving field. For example, Finite Element Modelling of Additive processes requires material property data which are not always readily available, especially when using non-standard alloys. Computational Thermodynamics, or the so-called CALPHAD approach can calculate properties such as specific heat, density, enthalpy, and mobilities, which can be used as inputs to other codes. These properties are expressed as functions of composition and temperature, which is useful since the additive process can impart large thermal and compositional gradients during a build. More advanced CALPHAD simulations that predict diffusional phase transformation and precipitation behaviour can also be used to determine the effect of not only solidification, but also repeated thermal cycling on the final microstructure. As thermal histories will be location specific in a build, these types of simulations can give insight into the local mechanical behaviour, when coupled with more advanced structure/property relationships. Several case studies have been highlighted to demonstrate the importance of computational thermodynamics in additive modelling.

Keyword: Thermodynamics, CALPHAD, Additive Manufacturing