Enhancing work hardening and ductility in additively manufactured β Ti: roles played by grain orientation, morphology and substructure
10 Apr 2022-Journal of Materials Science & Technology (Chinese Society of Metals)-Vol. 105, pp 131-141
TL;DR: In this article, a metastable β Ti alloy was additively manufactured by laser powder bed fusion (LPBF), and tensile testing along the build direction revealed significant work softening immediately following yielding with no uniform deformation.
About: This article is published in Journal of Materials Science & Technology.The article was published on 2022-04-10. It has received 10 citations till now. The article focuses on the topics: Materials science & Substructure.
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01 Jun 2022-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: A comprehensive overview of the research status, processing and heat treatment technologies, phase transformation, processing-microstructure-property correlation and strengthening-toughening mechanism of HS-TAs for aerospace engineering applications manufactured via melting-forging process is provided in this article .
Abstract: As a crucial branch for titanium industry, high-strength titanium alloys (HS-TAs, with UTS ≥ 1100 MPa) are indispensable structural materials for advanced engineering applications such as aerospace and marine fields. Along with the expansion of HS-TAs’ market, achieving satisfying synergies of high strength, high ductility (elongation ≥ 6%) and high toughness (KIC ≥ 50 MPa⋅m1/2) has been identified as the uppermost technical bottleneck for their research and development. To overcome the challenge, two primary strategies have been initiated by the titanium community, developing novel alloys and innovating processing technologies. For the former, a dozen of newly-developed alloys were reported to exhibit excellent strength-ductility-toughness combinations, including Ti-5553, BT22, TC21 and Ti-1300, for which the ideal mechanical performances were based on specific microstructures realized by low impurity rate (e.g. oxygen content ≤ 0.15 wt%), complicated processing and complex heat treatment. For the latter, several innovatory forging and heat treatment technologies were originated for the mature alloys to optimize their balanced property by extraordinary microstructural characteristics. In this review, we provide a comprehensive overview over the research status, processing and heat treatment technologies, phase transformation, processing-microstructure-property correlation and strengthening-toughening mechanism of HS-TAs for aerospace engineering applications manufactured via melting-forging process. Finally, the prospects and recommendations for further investigation and development are proposed based on this review.
98 citations
TL;DR: In this paper , a 3D texture control of β titanium-niobium alloy is proposed by fine-tuning the keyhole melt pool geometry and amount of overlap throughout the build.
Abstract: Fusion-based additive manufacturing (AM) offers a new opportunity to design metallic materials with complex, direction-dependent mechanical properties by controlling the orientation distribution of the constituent grains—also known as texture. Texture control may be achieved site-specifically by varying the processing variables and tailoring the local melt pool geometry and solidification kinetics. However, the type and direction of textures currently achievable in AM alloys are limited by the melt pool geometry itself. In this work, we advance the capabilities of controlling crystallographic texture in laser powder bed fusion (LPBF) by producing specimens of β titanium-niobium alloy with textures aligned along three different directions: the laser scan direction (SD), the build direction (BD), and—for the first time—the direction perpendicular to both BD and SD (i.e., PD). We achieve this three-dimensional (3-D) texture control by fine tuning the keyhole melt pool geometry and amount of overlap throughout the build. We test the tensile properties of the three different specimens along their respective texture axes and elucidate the relationships between crystallographic orientation, mesostructure, and mechanical behavior. We find that the novel PD texture exhibits the best combination of strength, strain hardenability, and ductility. We ascribe these results to the unique mesostructure of this specimen. This work opens new opportunities for designing novel materials with directional properties by achieving three-dimensional (3-D) texture control during fusion-based AM.
1 citations
01 Jan 2023
TL;DR: In this article , a laser powder bed fusion (L-PBF) in-situ alloying of Cu-8 wt.% Fe was reported, which achieved tensile strength of 462.9±6.6 MPa with 30.4%±1.7% elongation to failure and 74.5% IACS electrical conductivity.
Abstract: Liquid-liquid phase separation, and the resulted solute segregation, during conventional solidification have been a long-term challenge to produce copper (Cu)-iron (Fe) immiscible composites with high strength and high conductivity. The present work reports an effective solution to this issue through laser powder bed fusion (L-PBF) in-situ alloying of Cu-8 wt.% Fe. Microstructure observation showed that the fast cooling within micron-scale melt pools fully eliminated the Fe segregation and therefore the L-PBF fabricated nanocomposite achieved the homogeneous microstructure, which featured equiaxed fine grains around 1 µm in size. Ageing of the nanocomposite at 600°C for 1 h enabled precipitation of two types of nanoparticles. One is coarser Fe nanoprecipitates with body-centered cubic (BCC) structure and diameter of 100-300 nm, mainly distributing along grain boundaries. The other is smaller Fe nanoprecipitates with face-centered cubic (FCC) structure and diameter of 10-35 nm, being observed within the grains and having coherent interfaces with the Cu matrix. As a result, the aged Cu-Fe nanocomposite achieved tensile strength of 462.9±6.6 MPa with 30.4%±1.7% elongation to failure and 74.5% IACS (International Annealed Copper Standard) electrical conductivity. The formation mechanisms of the nanoprecipitates and the strengthening mechanisms of the nanocomposite are discussed.
1 citations
TL;DR: In this article , phase and microstructure evolution, mechanical properties and related mechanisms were systematically studied in as-cast Ti-7Mo-4Al-3Nb-2Cr-x Zr alloys.
Abstract: To refine the α s phase and form the nano twins, different contents of Zr were added to as-cast Ti–7Mo–4Al–3Nb–2Cr- x Zr alloys. Phase and microstructure evolution, mechanical properties and related mechanisms were systematically studied. Results show that as the Zr increases from 0 to 8 wt%, only α and β phases exist and the peak of β (110) shifts from 39.5 to 39.1° by XRD. The volume fraction of the α s phase changes from 75.4 to 73.9%, and its length decreases from 0.62 to 0.22 μm. More dislocations appear in the α/β interface and the growth twin of {10 1 ¯ 1} α < 11 2 ¯ 0> type with a width of ∼20 nm forms in α phase as observed by TEM. The refinement of the α s phase is due to the addition of Zr to promote nucleation and inhibit the growth rate. With increasing Zr content from 0 to 8 wt%, the strength increases from 961 to 1303 MPa, while the toughness decreases from 77 to 62 MPa m 1/2 . The fracture toughness decreases by 19.5%, while the strength increases by 35.6%. The refinement of α s phase, the solubilization of the Zr in the matrix, the increase of dislocation in the α/β interface, and the formation of nano twins are the main reasons for improving the strength and toughness of the studied alloys.
1 citations
TL;DR: In this article , the authors investigated the influence of the grain morphology and crystallographic orientation on the mechanical anisotropy of a laser powder bed fusion produced (L-PBFed) Ti-41Nb alloy using pre-alloyed alloy for dental implants.
References
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TL;DR: In this paper, the complexity and variety of fundamental phenomena in this material system with a focus on phase transformations and mechanical behaviour are discussed. And the challenges that lie ahead in achieving these goals are delineated.
1,797 citations
TL;DR: The following are described with regard to biomedical applications of titanium alloys: the Young's modulus, wear properties, notch fatigue strength, fatigue behaviour on relation to ageing treatment, and multifunctional deformation behaviours of Titanium alloys.
Abstract: Young's modulus as well as tensile strength, ductility, fatigue life, fretting fatigue life, wear properties, functionalities, etc., should be adjusted to levels that are suitable for structural biomaterials used in implants that replace hard tissue. These factors may be collectively referred to as mechanical biocompatibilities. In this paper, the following are described with regard to biomedical applications of titanium alloys: the Young's modulus, wear properties, notch fatigue strength, fatigue behaviour on relation to ageing treatment, improvement of fatigue strength, fatigue crack propagation resistance and ductility by the deformation-induced martensitic transformation of the unstable beta phase, and multifunctional deformation behaviours of titanium alloys.
1,022 citations
TL;DR: In this article, the authors investigated the anisotropic mechanical properties of a Ti-6Al-4V three-dimensional cruciform component fabricated using a directed energy deposition additive manufacturing (AM) process.
983 citations
TL;DR: In this paper, a new ultrafine lamellar microstructures comprising ultrafine (∼200-300nm) α-laths and retained β phases were created via promoting in situ decomposition of a near α′ martensitic structure in Ti-6Al-4V additively manufactured by selective laser melting (SLM).
839 citations
20 Oct 2014-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effect of the microstructure on the tensile properties of additive manufacturing (AM) of Ti alloys has been investigated. And the authors found that the mechanical anisotropy of the parts was discussed in relation to the crystallographic texture, phase composition and the predominant fracture mechanisms.
Abstract: Recent research on the additive manufacturing (AM) of Ti alloys has shown that the mechanical properties of the parts are affected by the characteristic microstructure that originates from the AM process. To understand the effect of the microstructure on the tensile properties, selective laser melted (SLM) Ti–6Al–4V samples built in three different orientations were tensile tested. The investigated samples were near fully dense, in two distinct conditions, as-built and stress relieved. It was found that the build orientation affects the tensile properties, and in particular the ductility of the samples. The mechanical anisotropy of the parts was discussed in relation to the crystallographic texture, phase composition and the predominant fracture mechanisms. Fractography and electron backscatter diffraction (EBSD) results indicate that the predominant fracture mechanism is intergranular fracture present along the grain boundaries and thus provide and explain the typical fracture surface features observed in fracture AM Ti–6Al–4V.
671 citations