| Abstract Scope |
This comparative computational study of Applied Calphad aims on the simulative analysis of mechanical properties and microstructures of IN718 and its recent C&W successors regarding their similar application at elevated temperatures. Predictions are presented for IN718, Alloy 720, AD730, Rene65, and M647. Moreover, due to a new C&W technology involving electro-slag remelting continuous directionally solidification, Rene88DT and derivatives GH4096 and FGH4096, as well as Co-free EXP-G27 completing the list of promising C&W candidates, are researched. Different alloying concepts are introduced, and their influence on microstructures during thermal processing is shown. Using the assessed MatCalc multi-component Calphad thermodynamics and diffusion mobilities databases „mc_ni“ for Ni-base superalloys within the system Ni-Fe-Al-Ti-Co-Cr-Mo-Nb-W, phase stabilities of Ni3Al-, Ni3Nb-, and Ni3Ti-based precipitates, relevant topologically close-packed structured intermetallics and their control by different alloying contributions are presented. Solubility behaviour of elements, and the thermodynamic dissolution behaviour of second phases in the Ni-fcc matrix are discussed. By Scheil-Gulliver simulations of as-cast microstructures, segregation trends during casting are described. The kinetic phase evolutions during sub- and supersolvus heat treatment conditions are evaluated with nucleation and growth modeling by using Matcalc, predicting particle distributions, sizes and densities. Process-related development of excess dislocations, and the impact of heterogeneous precipitates on the microstructural evolution, are considered in mean-field microstructural modeling with MatCalc.Potentials and limitations of the resulting prediction of strengthening behaviour, and dynamically recrystallised fractions, taking into account the computational thermokinetics of precipitation, are discussed. |