Microstructure and mechanical properties of a graded structural material

Ren, Honglei; Liu, D.; Tang, Hao; Tian, Xiangjun; Zhu, Ying; Wang, H.M.

doi:10.1016/j.msea.2014.06.016

Cited by 51 publications

(20 citation statements)

References 31 publications

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“…The key difference between solidification in AM and conventional casting technologies is that it involves the production of small melt pools (more similar to welding), and generates very high thermal gradients and cooling rates orders of magnitude higher than even high-pressure die casting. This leads to the development in turn of a very fine microstructure [185] and a tendency towards almost exclusively columnar growth particularly in Ti-based alloys [186][187][188][189].…”

Section: Outstanding Challengesmentioning

confidence: 99%

Recent advances in grain refinement of light metals and alloys

Easton

Qian

Prasad

et al. 2016

Current Opinion in Solid State and Materials Science

244

108

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Grain refinement leads, in general, to a decreased tendency to hot tearing, a more dispersed and refined porosity distribution, and improved directional feeding characteristics during solidification. Reduced as-cast grain size can also lead to improved mechanical properties and wrought processing by reducing the recrystallized grain size and achieving a fully recrystallized microstructure. It is now well established that the two key factors controlling grain refinement are the nucleant particles including their potency, size distribution and particle number density, and the rate of development of growth restriction, Q, generated by the alloy chemistry which establishes the undercooling needed to trigger nucleation events and facilitates their survival. The theories underpinning our current understanding of nucleation and grain formation are presented. The application of the latest theories to the light alloys of Al, Mg and Ti is explored as well as their applicability to a range of casting and solidification environments. In addition, processing by the application of physical processes such as external fields and additive manufacturing is discussed.To conclude, the current challenges for the development of reliable grain refining technologies for difficult to refine alloy systems will be presented.

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Section: Outstanding Challengesmentioning

confidence: 99%

Recent advances in grain refinement of light metals and alloys

Easton

Qian

Prasad

et al. 2016

Current Opinion in Solid State and Materials Science

244

108

View full text Add to dashboard Cite

show abstract

“…In particular, the directed energy deposition (DED) method, in which powder is fed into the melt pool under a moving laser [14], can be employed for FGM by varying the powder composition between layers, which is readily done using a deposition machine equipped with two or more powder feeders [15], [16]. This process has been used to prepare graded structures of titanium alloys [15]- [18]. However, as DED is a fusion-based process, the potential problems of dissimilar metal welding, namely, the formation of undesirable intermetallic phases, must be addressed [11], [19].…”

Section: Introductionmentioning

confidence: 99%

Functionally graded material of 304L stainless steel and inconel 625 fabricated by directed energy deposition: Characterization and thermodynamic modeling

et al. 2016

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Many engineering applications, particularly in extreme environments, require components with properties that vary with location in the part. Functionally graded materials (FGMs), which possess gradients in properties such as hardness or density, are a potential solution to address these requirements. The laser-based additive manufacturing process of directed energy deposition (DED) can be used to fabricate metallic parts with a gradient in composition by adjusting the volume fraction of metallic powders delivered to the melt pool as a function of position. As this is a fusion process, secondary phases may develop in the gradient zone during solidification that can result in undesirable properties in the part. This work describes experimental and thermodynamic studies of a component built from 304L stainless steel © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ incrementally graded to Inconel 625. The microstructure, chemistry, phase composition, and microhardness as a function of position were characterized by microscopy, energy dispersive spectroscopy, X-ray diffraction, and microindentation. Particles of secondary phases were found in small amounts within cracks in the gradient zone. These were ascertained to consist of transition metal carbides by experimental results and thermodynamic calculations. The study provides a combined experimental and thermodynamic computational modeling approach toward the fabrication and evaluation of a functionally graded material made by DED additive manufacturing.

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“…In fact, the tensile ductility and toughness of components in the building direction are higher than the transversal ones [71,73,74]. Previous research has established that epitaxial grain growth and consequently columnar grains is the common mechanism in most of the titanium alloys such as Ti-6Al-4V, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si and so on, and even in titanium aluminides alloys such as Ti-48Al-2Cr-2Nb [75][76][77]. However, in various direct laser deposited parts, different morphologies of prior beta grains were reported in near-alpha, α + β, and near-β titanium alloys.…”

Section: Microstructurementioning

confidence: 99%

An Overview of Additive Manufacturing of Titanium Components by Directed Energy Deposition: Microstructure and Mechanical Properties

et al. 2017

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The directed energy deposition (DED) process can be employed to build net shape components or prototypes starting from powder or wires, through a layer-by-layer process. This process provides an opportunity to fabricate complex shaped and functionally graded parts that can be utilized in different engineering applications. DED uses a laser as a focused heat source to melt the in-situ delivered powder or wire-shaped raw materials. In the past years extensive studies on DED have shown that this process has great potential in order to be used for (i) rapid prototyping of metallic parts, (ii) fabrication of complex and customized parts, (iii) repairing/cladding valuable components which cannot be repaired by other traditional techniques. However, the industrial adoption of this process is still challenging owing to the lack of knowledge on the mechanical performances of the constructed components and also on the trustworthiness/durability of engineering parts produced by DED. This manuscript provides an overview of the additive manufacturing (AM) of titanium alloys and focuses in particular on the mechanical properties and microstructure of components fabricated by DED.

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Microstructure and mechanical properties of a graded structural material

Cited by 51 publications

References 31 publications

Recent advances in grain refinement of light metals and alloys

Recent advances in grain refinement of light metals and alloys

Functionally graded material of 304L stainless steel and inconel 625 fabricated by directed energy deposition: Characterization and thermodynamic modeling

An Overview of Additive Manufacturing of Titanium Components by Directed Energy Deposition: Microstructure and Mechanical Properties

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