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In functionally graded materials (FGMs) fabricated using directed energy deposition (DED) additive manufacturing (AM), cracks may form due to interdendritic stress during solidification, the formation of deleterious phases, or the buildup of residual stresses. This study builds on our previously proposed concept of FGM feasibility diagrams to identify gradient pathways that avoid deleterious phases in FGMs by also considering hot cracking. Here, five hot cracking criteria were integrated into the feasibility diagrams, and equilibrium simulations were carried out based on Scheil results (termed hybrid Scheil-equilibrium simulation) to predict phase formation below the solidus temperature considering solidification micro-segregation. The new feasibility diagrams were applied to four previously studied FGMs, and the newly proposed approach predicted high crack susceptibility, detrimental phase formation, or interdendritic BCC phase formation in the experimentally observed cracking region. This demonstrates the utility of the proposed framework for crack prediction in the design of future FGMs gradient pathways.
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AMMap tool for additive manufacturing design, alloy discovery, and path planning
Compositionally complex materials (CCMs), such as functionally graded materials (FGMs) made by additive manufacturing (AM) often form undesired phases or cracks, negatively affecting the build. Equilibrium thermodynamic calculations and solidification simulations, such as Scheil–Gulliver, can be used to predict feasible compositions or compositional paths, acting as constraints before empirical or machine learning models are applied to predict properties of interest. In addition, additional analysis of solidification simulations can be used to predict hot-cracking using various criteria to further account for manufacturability. To define and navigate the high order chemical systems of CCMs/FGMs, the open-source tool, AMMap, has been developed utilizing open models and CALPHAD methods for thermodynamic computation. AMMap explores spaces constructed with the nimplex library, using a novel algorithm to represent high-dimensional systems as graphs that can be joined into homogeneous structures and explored with graph traversal algorithms to automate the path-design process. This method allows the use of existing high-performance gradient descent, graph traversal search, and other path optimization algorithms to automate the path-design process with as little prior bias as possible.
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- Award ID(s):
- 2050069
- PAR ID:
- 10680634
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Journal of Physics: Materials
- Volume:
- 8
- Issue:
- 3
- ISSN:
- 2515-7639
- Page Range / eLocation ID:
- 035008
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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