A fully kinetic phase diagram-coupled multicomponent columnar-to-equiaxed grain transition model with an application to additive manufacturing AITranslate

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DOI：https://doi.org/10.1016/j.calphad.2023.102642

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The columnar-to-equiaxed transition (CET) is known to impact crack formation during the additive manufacturing of metallic alloys. While previous experiments have shown that CET is tunable via its alloying elements, a rigorous multicomponent model to demonstrate the impact of multi-alloying components on CET is still lacking. In this study, we developed a multicomponent model by fully coupling the phase diagram of the kinetic interface condition. Building upon the binary model reported by Gaumann et al. our model replaces the restrictive approach of calculating the non-equilibrium partition coefficient and liquidus slopes with kinetic phase diagram calculation. The extended multicomponent model was validated by comparing it with the Al–Cu results reported by Gaumann et al. CET transition curves were computed for two Al–Cu–Mg–Si–Zn alloys manufactured using laser powder bed fusion. The results are in qualitative agreement with our own and previously reported experimental results. These findings suggest that the proposed multicomponent CET model is a valuable tool for designing AM alloys and optimising processing parameters. Graphical abstract The figure above shows the predicted columnar to equiaxed transitions curve of Al-1.6 wt%Cu-2.56 wt%Mg-1.2 wt%Si-5.44 wt%Zn (original AA7075) and Al-1.6 wt%Cu-2.56 wt%Mg-5.0 wt%Si-5.44 wt%Zn (Si rich AA7075) alloys. For a given temperature gradient, the addition of Si greatly reduces the critical interface growth rate for Columnar to Equiaxed Transition (CET) thus promoting CET. The prediction is in good agreement with the two alloys grain morphology shown with EBSD orientation map in the figure below. The EBSD orientation maps of (a) an original 7075 alloy sample and (b) Si-rich AA7075 alloy. The observed plane is parallel to the building direction. It is color-coded by inverse pole figure, and black lines indicate grain boundaries. Download : Download high-res image (313KB) Download : Download full-size image