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Nickel-based superalloys (Ni-alloys) are widely used in flight-critical aeroengine components because of their excellent material properties at high temperatures such as yield strength, ductility, and creep resistance. However, these desirable high-temperature properties also make Ni-alloys very difficult to machine. This paper provides an overview and benchmarking of various constitutive models to provide the process modeling community with an objective comparison between various calibrated material models, to increase the accuracy of process model predictions for machining of Ni-alloys. Various studies involving the Johnson-Cook model and the calibration of its constants in finite element simulations are discussed. Significant discrepancies exist between researchers' approaches to calibrating constitutive models. Moreover, this paper provides a comprehensive overview of pedigreed physical material properties for a range of Ni-alloys. In this context, the variation of thermal properties and thermally induced stresses over machining temperature regimes are modeled for a variety of Ni-alloys. The chemical compositions and applications for a range of relevant Ni-alloys are also explored. Overall, this manuscript identifies the need for more comprehensive analysis and process-specific characterization of thermomechanical properties for difficult-to-machine Ni-alloys to improve machining performance and aeroengine component quality.
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Increased ductility of Ti-6Al-4V by interlayer milling during directed energy deposition
Additive manufacturing (AM) often results in high strength but poor ductility in titanium alloys. Hybrid AM is a solution capable of improving both ductility and strength. In this study, hybrid AM of Ti-6Al-4 V was achieved by coupling directed energy deposition with interlayer machining. The microstructure, residual stress, and microhardness were examined to explain how interlayer machining caused a 63% improvement in ductility while retaining an equivalent strength to as-printed samples. Interlayer machining introduced recurrent interruptions in printing that allowed for slow cooling-induced coarsening of acicular α laths at the machined interfaces. The coarse α laths on the selectively machined layers increased dislocation motion under tensile loads and improved bulk ductility. The results highlighted in this publication demonstrate the feasibility of hybrid AM to enhance the toughness of titanium alloys.
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- Award ID(s):
- 2318705
- PAR ID:
- 10547449
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Additive Manufacturing
- Volume:
- 78
- Issue:
- C
- ISSN:
- 2214-8604
- Page Range / eLocation ID:
- 103818
- Subject(s) / Keyword(s):
- Hybrid additive manufacturing Milling Directed energy deposition Titanium
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.addma.2023.103818
