Mechanical property heterogeneity in additively manufactured nickel superalloy

Forsey, Alexander N.; Das, Yadunandan; Simm, Thomas H.; Clark, Dean S.; Boswell, John; Güngör, S.; Moat, Richard

doi:10.1016/j.msea.2017.12.025

Cited by 7 publications

(2 citation statements)

References 21 publications

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“…A strong fiber texture exists within the epitaxial β grains orientated in the <001> directions parallel to the build [22]. Experimental techniques have used digital image correlation to investigate heterogeneous deformation and strain accumulation relative to the microstructural features in additively manufactured materials, including Ti64 [9,13] and other material systems [23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Modeling the Role of Epitaxial Grain Structure of the Prior β Phase and Associated Fiber Texture on the Strength Characteristics of Ti-6Al-4V Produced via Additive Manufacturing

et al. 2020

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Due to the rapid cooling and directional heat flow inherent in metal-based additive manufacturing, Ti-6Al-4V results in epitaxial grain growth and a fiber texture of the prior β phase. While Ti-6Al-4V produced via powder bed, electron beam melted processing can exhibit a range of strength characteristics, recent studies have shown superior strength properties, compared to similar orientations, of conventional plate material (AMS 4911) across a range of elevated temperatures (204 to 371 °C). To investigate this phenomenon, a series of crystal plasticity models was developed for the representative grain structures of Ti-6Al-4V to rationalize if the columnar, fiber texture produced by additive manufacturing (AM) was sufficient to explain the observed strength attributes. As a first step towards understanding this behavior, the grain structure was characterized via electron backscattering diffraction for AM material taken from four specimens (with different build directions), as well as material taken from baseline plate material (along and transverse to the rolling direction), and the resulting microstructures were modeled via a crystal plasticity framework. As expected, the results showed the AM material accounting for only the α grain structure was stronger in the vertical builds and weaker in the horizontal builds compared to the conventional plate counterparts. This suggested that grain morphology and α grain orientation alone provided some information about the relative strengths, but did not explain the overall trends observed from the experiments. To account for the role of texture, the characterized α phase was converted, via variant selection, to its prior β phase for use in the simulations. The results showed that each simulation of the AM prior β phase exhibited a higher strength compared to the baseline plate material, except for one specimen (horizontally built), which had large colonies of soft microtextured regions for the prior β structure. This suggests that some variability was experienced (as anticipated), but the texture (especially of the prior β macrozones) was a key contributor for the unusually high strength observed of the AM Ti-6Al-4V material.

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Section: Introductionmentioning

confidence: 99%

Modeling the Role of Epitaxial Grain Structure of the Prior β Phase and Associated Fiber Texture on the Strength Characteristics of Ti-6Al-4V Produced via Additive Manufacturing

et al. 2020

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“…However, this is at the expense of a smaller measured volume and Journal Pre-proof J o u r n a l P r e -p r o o f 3 information being obtained for a surface only. Electron microscopy is commonly employed to characterise plastic deformation by utilising information via electron backscatter diffraction (EBSD) and digital image correlation (DIC) [7][8][9][10]. They can be used to give information about local changes in grain shape and size, different phases, orientation, dislocation density and surface strain.…”

Section: Introductionmentioning

confidence: 99%

The τ-plot, a multicomponent 1-D pole figure plot, to quantify the heterogeneity of plastic deformation

Simm

Das

Forsey

et al. 2020

Materials Characterization

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An approach is presented that allows multi-scale characterisations of heterogeneous deformation in crystalline materials by employing a range of characterisation techniques including: electron backscatter diffraction, digital image correlation and neutron diffraction powder measurements. The approach will be used to obtain critical information about the variations in parameters that characterise the deformed state in different crystallographic orientation texture components of a sample in a statistically significant way. These parameters include lattice strains, texture evolution, peak broadening, dislocation density, planar faults, phase changes and surface strain. This approach allows verification of models of plastic deformation to provide a more detailed view of plastic deformation heterogeneity at multiple length scales than obtained by other characterisation approaches. The approach demonstrated here is applied to two stainless steel alloys; an alloy that exhibits phase transformation during deformation and an alloy that remains the same phase all through deformation process.

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High-density direct laser deposition (DLD) of CM247LC alloy: microstructure, porosity and cracks

Bidare

Mehmeti

Jiménez

et al. 2022

Int J Adv Manuf Technol

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Nickel-based alloys are known as non-weldable materials due to their complex characteristics. Consequently, additive manufacturing of these alloys is particularly challenging. In this paper, the influence of process parameters on the porosity, crack formation and microstructure of additively manufactured CM247LC nickel-based alloy is analysed. The feasibility of the direct laser deposition (DLD) process to manufacture crack-free and low-porosity CM247LC samples is studied. CM247LC samples were built on Inconel 718 that has similar chemical composition, to form hybrid superalloy parts. It was shown that crack-free and high-density CM247LC samples can be obtained through DLD without significant substrate preheating for certain parameter combinations: laser power in the range of 800–1000 W and powder feed rates between 6 and 8 g/min. High-cost and complex preheating was avoided that was commonly reported as necessary to achieve similar densities. For hybrid parts, a large beam diameter and slow scan speeds were employed to achieve optimal conditions as it was evident from the achieved bonding between the Inconel 718 substrate and the deposited layers. It was observed that good bonding between the two materials can be obtained with laser power values between 800 and 1000 W, scanning speed higher than 300 mm/min and powder flow rates of 6–8 g/min.

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Mechanical property heterogeneity in additively manufactured nickel superalloy

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Cited by 7 publications

References 21 publications

Modeling the Role of Epitaxial Grain Structure of the Prior β Phase and Associated Fiber Texture on the Strength Characteristics of Ti-6Al-4V Produced via Additive Manufacturing

Modeling the Role of Epitaxial Grain Structure of the Prior β Phase and Associated Fiber Texture on the Strength Characteristics of Ti-6Al-4V Produced via Additive Manufacturing

The τ-plot, a multicomponent 1-D pole figure plot, to quantify the heterogeneity of plastic deformation

High-density direct laser deposition (DLD) of CM247LC alloy: microstructure, porosity and cracks

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