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Crystals 2017, 7(11), 334;

Morphology Dependent Flow Stress in Nickel-Based Superalloys in the Multi-Scale Crystal Plasticity Framework

National Institute of Standards and Technology/Theiss Research, 7411 Eads Ave, La Jolla, CA 92037, USA
Department of Materials Engineering, Purdue University, 701 West Stadium Avenue, West Lafayette, IN 47907, USA
National Institute of Standards and Technology, 100 Bureau Dr, Gaithersburg, MD 20899, USA
Author to whom correspondence should be addressed.
Received: 18 September 2017 / Revised: 19 October 2017 / Accepted: 26 October 2017 / Published: 2 November 2017
(This article belongs to the Special Issue Crystal Dislocations: Their Impact on Physical Properties of Crystals)
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This paper develops a framework to obtain the flow stress of nickel-based superalloys as a function of γ-γ’ morphology. The yield strength is a major factor in the design of these alloys. This work provides additional effects of γ’ morphology in the design scope that has been adopted for the model developed by authors. In general, the two-phase γ-γ’ morphology in nickel-based superalloys can be divided into three variables including γ’ shape, γ’ volume fraction and γ’ size in the sub-grain microstructure. In order to obtain the flow stress, non-Schmid crystal plasticity constitutive models at two length scales are employed and bridged through a homogenized multi-scale framework. The multi-scale framework includes two sub-grain and homogenized grain scales. For the sub-grain scale, a size-dependent, dislocation-density-based finite element model (FEM) of the representative volume element (RVE) with explicit depiction of the γ-γ’ morphology is developed as a building block for the homogenization. For the next scale, an activation-energy-based crystal plasticity model is developed for the homogenized single crystal of Ni-based superalloys. The constitutive models address the thermo-mechanical behavior of nickel-based superalloys for a large temperature range and include orientation dependencies and tension-compression asymmetry. This homogenized model is used to obtain the morphology dependence on the flow stress in nickel-based superalloys and can significantly expedite crystal plasticity FE simulations in polycrystalline microstructures, as well as higher scale FE models in order to cast and design superalloys. View Full-Text
Keywords: flow stress; morphology; Ni-based superalloys; homogenization; crystal plasticity flow stress; morphology; Ni-based superalloys; homogenization; crystal plasticity

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Keshavarz, S.; Molaeinia, Z.; Reid, A.; Langer, S. Morphology Dependent Flow Stress in Nickel-Based Superalloys in the Multi-Scale Crystal Plasticity Framework. Crystals 2017, 7, 334.

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