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At least 271 records · Page 15
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DOE OSTI2020

Materials Data on Ti(VTe2)2 by Materials Project

Ti(VTe2)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Ti4+ is bonded to six Te2- atoms to form TiTe6 octahedra that share corners with twelve equivalent VTe6 octahedra, edges with two equivalent TiTe6 octahedra, and faces with two equivalent VTe6 octahedra. The corner-sharing octahedra tilt angles range from 49–56°. There are two shorter (2.79 Å) and four longer (2.84 Å) Ti–Te bond lengths. V2+ is bonded to six Te2- atoms to form VTe6 octahedra that share corners with six equivalent TiTe6 octahedra, edges with six equivalent VTe6 octahedra, and a faceface with one TiTe6 octahedra. The corner-sharing octahedra tilt angles range from 49–56°. There are a spread of V–Te bond distances ranging from 2.70–2.92 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ti4+ and three equivalent V2+ atoms. In the second Te2- site, Te2- is bonded in a distorted rectangular see-saw-like geometry to one Ti4+ and three equivalent V2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(CrTe2)2 by Materials Project

Ti(CrTe2)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Ti4+ is bonded to six Te2- atoms to form TiTe6 octahedra that share corners with twelve equivalent CrTe6 octahedra, edges with two equivalent TiTe6 octahedra, and faces with two equivalent CrTe6 octahedra. The corner-sharing octahedra tilt angles range from 50–51°. There are two shorter (2.79 Å) and four longer (2.83 Å) Ti–Te bond lengths. Cr2+ is bonded to six Te2- atoms to form CrTe6 octahedra that share corners with six equivalent TiTe6 octahedra, edges with six equivalent CrTe6 octahedra, and a faceface with one TiTe6 octahedra. The corner-sharing octahedra tilt angles range from 50–51°. There are a spread of Cr–Te bond distances ranging from 2.72–2.84 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ti4+ and three equivalent Cr2+ atoms. In the second Te2- site, Te2- is bonded in a rectangular see-saw-like geometry to one Ti4+ and three equivalent Cr2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(Si3Mo)2 by Materials Project

Ti(MoSi3)2 is Titanium Disilicide-derived structured and crystallizes in the orthorhombic C222 space group. The structure is three-dimensional. Ti4+ is bonded in a distorted q6 geometry to ten Si+1.33- atoms. There are a spread of Ti–Si bond distances ranging from 2.56–2.77 Å. Mo2+ is bonded in a distorted q6 geometry to ten Si+1.33- atoms. There are a spread of Mo–Si bond distances ranging from 2.57–2.75 Å. There are two inequivalent Si+1.33- sites. In the first Si+1.33- site, Si+1.33- is bonded in a 10-coordinate geometry to three equivalent Ti4+, two equivalent Mo2+, and five Si+1.33- atoms. There are a spread of Si–Si bond distances ranging from 2.51–2.79 Å. In the second Si+1.33- site, Si+1.33- is bonded in a 10-coordinate geometry to one Ti4+, four equivalent Mo2+, and five Si+1.33- atoms. There are a spread of Si–Si bond distances ranging from 2.56–2.77 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(NbS2)4 by Materials Project

Ti(NbS2)4 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ti4+ is bonded to six equivalent S2- atoms to form TiS6 octahedra that share corners with twelve equivalent NbS6 pentagonal pyramids and faces with two equivalent NbS6 pentagonal pyramids. All Ti–S bond lengths are 2.45 Å. There are two inequivalent Nb3+ sites. In the first Nb3+ site, Nb3+ is bonded to six equivalent S2- atoms to form distorted NbS6 pentagonal pyramids that share edges with six equivalent NbS6 pentagonal pyramids and faces with two equivalent TiS6 octahedra. All Nb–S bond lengths are 2.51 Å. In the second Nb3+ site, Nb3+ is bonded to six S2- atoms to form distorted NbS6 pentagonal pyramids that share corners with four equivalent TiS6 octahedra and edges with six NbS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 47°. There are two shorter (2.46 Å) and four longer (2.53 Å) Nb–S bond lengths. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent Nb3+ atoms. In the second S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to one Ti4+ and three Nb3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(FeO2)3 by Materials Project

Ti(FeO2)3 is Ilmenite-like structured and crystallizes in the trigonal R3 space group. The structure is three-dimensional. Ti4+ is bonded to six O2- atoms to form distorted TiO6 octahedra that share corners with nine FeO6 octahedra, edges with three equivalent FeO6 octahedra, and a faceface with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 49–57°. There are three shorter (1.92 Å) and three longer (2.09 Å) Ti–O bond lengths. There are three inequivalent Fe+2.67+ sites. In the first Fe+2.67+ site, Fe+2.67+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with three equivalent FeO6 octahedra, corners with six equivalent TiO6 octahedra, edges with three equivalent FeO6 octahedra, and a faceface with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 49–64°. There are three shorter (2.08 Å) and three longer (2.25 Å) Fe–O bond lengths. In the second Fe+2.67+ site, Fe+2.67+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with three equivalent TiO6 octahedra, corners with six equivalent FeO6 octahedra, edges with three equivalent FeO6 octahedra, and a faceface with one TiO6 octahedra. The corner-sharing octahedra tilt angles range from 44–57°. There are three shorter (2.02 Å) and three longer (2.09 Å) Fe–O bond lengths. In the third Fe+2.67+ site, Fe+2.67+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with nine FeO6 octahedra, edges with three equivalent TiO6 octahedra, and a faceface with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 44–64°. There are three shorter (1.98 Å) and three longer (2.15 Å) Fe–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to one Ti4+ and three Fe+2.67+ atoms to form a mixture of distorted edge and corner-sharing OTiFe3 trigonal pyramids. In the second O2- site, O2- is bonded in a distorted see-saw-like geometry to one Ti4+ and three Fe+2.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(MoS2)2 by Materials Project

Ti(MoS2)2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. Ti4+ is bonded to six S2- atoms to form distorted TiS6 octahedra that share corners with six equivalent MoS6 octahedra, edges with two equivalent TiS6 octahedra, edges with four equivalent MoS6 octahedra, and a faceface with one MoS6 octahedra. The corner-sharing octahedra tilt angles range from 49–55°. There are a spread of Ti–S bond distances ranging from 2.40–2.62 Å. There are two inequivalent Mo2+ sites. In the first Mo2+ site, Mo2+ is bonded to six S2- atoms to form distorted MoS6 octahedra that share corners with six equivalent MoS6 octahedra, edges with two equivalent MoS6 octahedra, edges with four equivalent TiS6 octahedra, and a faceface with one MoS6 octahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are a spread of Mo–S bond distances ranging from 2.39–2.61 Å. In the second Mo2+ site, Mo2+ is bonded to six S2- atoms to form MoS6 octahedra that share corners with six equivalent TiS6 octahedra, corners with six equivalent MoS6 octahedra, edges with two equivalent MoS6 octahedra, a faceface with one TiS6 octahedra, and a faceface with one MoS6 octahedra. The corner-sharing octahedra tilt angles range from 49–56°. There are a spread of Mo–S bond distances ranging from 2.39–2.48 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to one Ti4+ and three Mo2+ atoms. In the second S2- site, S2- is bonded in a 4-coordinate geometry to two equivalent Ti4+ and two Mo2+ atoms. In the third S2- site, S2- is bonded in a 5-coordinate geometry to one Ti4+ and four Mo2+ atoms. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Ti4+ and three Mo2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(HO)2 by Materials Project

Ti(OH)2 crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. Ti2+ is bonded to six equivalent O2- atoms to form a mixture of distorted edge and corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are four shorter (2.20 Å) and two longer (2.25 Å) Ti–O bond lengths. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. O2- is bonded in a distorted single-bond geometry to three equivalent Ti2+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(CrSi3)2 by Materials Project

Ti(CrSi3)2 is Titanium Disilicide-derived structured and crystallizes in the orthorhombic C222 space group. The structure is three-dimensional. Ti4+ is bonded in a distorted q6 geometry to ten Si+1.33- atoms. There are a spread of Ti–Si bond distances ranging from 2.53–2.66 Å. Cr2+ is bonded in a distorted q6 geometry to ten Si+1.33- atoms. There are a spread of Cr–Si bond distances ranging from 2.46–2.66 Å. There are two inequivalent Si+1.33- sites. In the first Si+1.33- site, Si+1.33- is bonded in a 10-coordinate geometry to three equivalent Ti4+, two equivalent Cr2+, and five Si+1.33- atoms. There are a spread of Si–Si bond distances ranging from 2.48–2.68 Å. In the second Si+1.33- site, Si+1.33- is bonded in a 10-coordinate geometry to one Ti4+, four equivalent Cr2+, and five Si+1.33- atoms. There are a spread of Si–Si bond distances ranging from 2.46–2.71 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(NbSe2)3 by Materials Project

Ti(NbSe2)3 is Ilmenite-like structured and crystallizes in the hexagonal P6_322 space group. The structure is three-dimensional. Ti4+ is bonded to six equivalent Se2- atoms to form TiSe6 octahedra that share corners with twelve NbSe6 pentagonal pyramids and faces with two equivalent NbSe6 pentagonal pyramids. All Ti–Se bond lengths are 2.59 Å. There are two inequivalent Nb+2.67+ sites. In the first Nb+2.67+ site, Nb+2.67+ is bonded to six equivalent Se2- atoms to form distorted NbSe6 pentagonal pyramids that share corners with six equivalent TiSe6 octahedra and edges with six equivalent NbSe6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 46°. All Nb–Se bond lengths are 2.62 Å. In the second Nb+2.67+ site, Nb+2.67+ is bonded to six equivalent Se2- atoms to form distorted NbSe6 pentagonal pyramids that share corners with three equivalent TiSe6 octahedra, edges with six NbSe6 pentagonal pyramids, and a faceface with one TiSe6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are three shorter (2.62 Å) and three longer (2.64 Å) Nb–Se bond lengths. Se2- is bonded to one Ti4+ and three Nb+2.67+ atoms to form a mixture of distorted edge, corner, and face-sharing SeTiNb3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(FeSe2)2 by Materials Project

Ti(FeSe2)2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. Ti4+ is bonded to six Se2- atoms to form distorted TiSe6 octahedra that share corners with six equivalent FeSe6 octahedra, edges with two equivalent TiSe6 octahedra, edges with four equivalent FeSe6 octahedra, and a faceface with one FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 53–58°. There are a spread of Ti–Se bond distances ranging from 2.44–2.74 Å. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six Se2- atoms to form FeSe6 octahedra that share corners with six equivalent TiSe6 octahedra, corners with six equivalent FeSe6 octahedra, edges with two equivalent FeSe6 octahedra, a faceface with one TiSe6 octahedra, and a faceface with one FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 49–58°. There are a spread of Fe–Se bond distances ranging from 2.44–2.58 Å. In the second Fe2+ site, Fe2+ is bonded to six Se2- atoms to form FeSe6 octahedra that share corners with six equivalent FeSe6 octahedra, edges with two equivalent FeSe6 octahedra, edges with four equivalent TiSe6 octahedra, and a faceface with one FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 49–56°. There are a spread of Fe–Se bond distances ranging from 2.41–2.59 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Ti4+ and three Fe2+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to one Ti4+ and four Fe2+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent Ti4+ and two Fe2+ atoms. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to one Ti4+ and three Fe2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(CrS2)2 by Materials Project

Ti(CrS2)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Ti4+ is bonded to six S2- atoms to form TiS6 octahedra that share corners with twelve equivalent CrS6 octahedra, edges with two equivalent TiS6 octahedra, and faces with two equivalent CrS6 octahedra. The corner-sharing octahedra tilt angles range from 49–50°. There are two shorter (2.45 Å) and four longer (2.50 Å) Ti–S bond lengths. Cr2+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with six equivalent TiS6 octahedra, edges with six equivalent CrS6 octahedra, and a faceface with one TiS6 octahedra. The corner-sharing octahedra tilt angles range from 49–50°. There are a spread of Cr–S bond distances ranging from 2.37–2.47 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a rectangular see-saw-like geometry to one Ti4+ and three equivalent Cr2+ atoms. In the second S2- site, S2- is bonded to two equivalent Ti4+ and three equivalent Cr2+ atoms to form a mixture of distorted corner and edge-sharing STi2Cr3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(CrS2)2 by Materials Project

Ti(CrS2)2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. Ti4+ is bonded to six S2- atoms to form TiS6 octahedra that share corners with six equivalent CrS6 octahedra, edges with two equivalent TiS6 octahedra, edges with four equivalent CrS6 octahedra, and a faceface with one CrS6 octahedra. The corner-sharing octahedra tilt angles range from 50–52°. There are a spread of Ti–S bond distances ranging from 2.38–2.57 Å. There are two inequivalent Cr2+ sites. In the first Cr2+ site, Cr2+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with six equivalent CrS6 octahedra, edges with two equivalent CrS6 octahedra, edges with four equivalent TiS6 octahedra, and a faceface with one CrS6 octahedra. The corner-sharing octahedra tilt angles range from 48–53°. There are a spread of Cr–S bond distances ranging from 2.35–2.50 Å. In the second Cr2+ site, Cr2+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with six equivalent TiS6 octahedra, corners with six equivalent CrS6 octahedra, edges with two equivalent CrS6 octahedra, a faceface with one TiS6 octahedra, and a faceface with one CrS6 octahedra. The corner-sharing octahedra tilt angles range from 48–53°. There are a spread of Cr–S bond distances ranging from 2.39–2.46 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Ti4+ and three Cr2+ atoms. In the second S2- site, S2- is bonded to one Ti4+ and four Cr2+ atoms to form distorted edge-sharing STiCr4 trigonal bipyramids. In the third S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to one Ti4+ and three Cr2+ atoms. In the fourth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ti4+ and two Cr2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(NbS2)3 by Materials Project

Ti(NbS2)3 is Ilmenite-like structured and crystallizes in the hexagonal P6_322 space group. The structure is three-dimensional. Ti4+ is bonded to six equivalent S2- atoms to form TiS6 octahedra that share corners with twelve NbS6 pentagonal pyramids and faces with two equivalent NbS6 pentagonal pyramids. All Ti–S bond lengths are 2.47 Å. There are two inequivalent Nb+2.67+ sites. In the first Nb+2.67+ site, Nb+2.67+ is bonded to six equivalent S2- atoms to form distorted NbS6 pentagonal pyramids that share corners with six equivalent TiS6 octahedra and edges with six equivalent NbS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 45°. All Nb–S bond lengths are 2.50 Å. In the second Nb+2.67+ site, Nb+2.67+ is bonded to six equivalent S2- atoms to form distorted NbS6 pentagonal pyramids that share corners with three equivalent TiS6 octahedra, edges with six NbS6 pentagonal pyramids, and a faceface with one TiS6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are three shorter (2.50 Å) and three longer (2.51 Å) Nb–S bond lengths. S2- is bonded to one Ti4+ and three Nb+2.67+ atoms to form a mixture of distorted corner, edge, and face-sharing STiNb3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Local Environment of Superoxide Radical Formed on the TiO 2 Surface Produced From Ti(OiPr) 4 Exposed to H 2 O 2

A selective heterogeneous catalyst with the superoxide anion O 2 •– stable at room temperature, generated by treating Ti(OR) 4 (R=iPr, nBu) with H 2 O 2 , was previously reported and used for the oxidation of organic compounds. Furthermore, it was proposed that exceptional stability of the O 2 •– is resulted from its stabilization near Ti +4 cation on the TiO 2 surface with participation of water molecules and/or OH groups. In this article, we performed high-resolution pulsed EPR study on the O 2 •– in this catalyst with the aim to obtain quantitative information about its interactions with the surrounding molecules. Our data has shown that the O 2 •– is involved in weak hyperfine interactions with protons in the nearest environment, which do not exceed a value of 2 MHz. It corresponds to an Os…H distance of ≥ 3 Å that exclude the formation of hydrogen bonds. The analysis of possible structures of O 2 •– adsorption on TiO 2 surface taking into account our results and lack of radical mobility at room temperature previously observed in EPR spectra led us to suggest that the O 2 •– is stabilized in the form of superoxo bridge coordinated with two titanium atoms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Preliminary Study on Machining of Additively Manufactured Ti-6Al-4V

We report additively manufactured metals differ from their conventionally produced counterparts due to the inherent material inhomogeneity, porosity, and thermal stress induced by the process. These differences make the machining of additively manufactured metals more difficult and cause premature tool failure or unexpected surface finish at certain conditions. This study takes the first step to investigate and identify the causes of these issues, particularly for Ti-6Al-4V. Printed and wrought samples, as well as heat treatment effect, are compared in a dry cutting condition at a cutting speed of 90 m/min in terms of cutting power, vibration, temperature, and produced surface finish. The results show a lower cutting power and more vibration for as-printed Ti samples, indicating a less ductile microstructure and inclusion of pores. Heat treatment can eliminate these phenomena. There is no significant difference found in the produced surface finish at the current cutting condition.

36 MATERIALS SCIENCE↗
DOE OSTI2022

On the Prediction of Uniaxial Tensile Behavior Beyond the Yield Point of Wrought and Additively Manufactured Ti-6Al-4V

In this paper, phenomenological relationships are presented that permit the prediction of the plastic regime of stress–strain curves using a limited number of parameters. These relationships were obtained from both conventional (wrought + β annealed) and additively manufactured (i.e., “3D printed”) Ti-6Al-4V. Three different methods of additive manufacturing have been exploited to produce the materials, including large-volume electron beam additive manufacturing, large-volume laser hot wire additive manufacturing, and small-volume selective laser melting. The general fundamental expressions are independent not only of the additive manufacturing process, but also of a wide variety of post-deposition heat treatments, however the coefficients are specific to material states. Thus, this work demonstrates that it is possible to predict not only the ultimate tensile strength, but also the full true stress, true strain curves, if certain parameters of the material are known. In general, the prediction of ultimate tensile strength are within 5% of the experimentally measured values across all additive manufacturing variants and subsequent heat treatments. The absolute values of ultimate tensile strength range from ~ 910 MPa to ~ 1170 MPa for the single alloy Ti-6Al-4V. Data representing 113 explicit samples are included in this work.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Modeling the role of local crystallographic correlations in microstructures of Ti-6Al-4V using a correlated structure visco-plastic self-consistent polycrystal plasticity formulation

This paper presents a multi-level crystal plasticity-based simulation framework for modeling mechanical response and microstructure evolution of Ti-6Al-4V with α-lath/lamellar microstructures. Here, the model is a correlated structure visco-plastic self-consistent (CS-VPSC) formulation linking three scales: a single crystals micro-scale, a lath/lamellar colony meso-scale, and a lath/lamellar aggregate macro-scale. A selected hardening law for the evolution of critical resolved shear stress per slip system used in CS-VPSC is phenomenological. However, it adjusts the resistances of basal and prismatic slip systems based on the geometry of slip transfer between adjacent lamellae. Consistent with experimental evidences, the resolved shear stress on the pyramidal slip planes is dependent not only on the stress in the direction of slip but also on the two orthogonal shear stress components and the three normal stress components (non-Schmid effects). Electron backscatter diffraction (EBSD) data in conjunction with a procedure relying on α→β phase transformation is used to construct paired variants of α-laths/lamellae satisfying their local crystallographic correlations. The procedure fits volume fractions of individual laths/lamellae with the experimental EBSD data and selects a distribution of habit planes between adjacent variants with respect to the loading direction. The simulation framework is applied to interpret the deformation behavior in tension and compression along two sample directions of Ti-6Al-4V fabricated via laser powder bed fusion. Moreover, the model is used to simulate texture evolution during rolling of the material to large strains. It is demonstrated that the model is capable of predicting plastic anisotropy/asymmetry and the concomitant texture evolution. While the model reveals a significant effect of habit plane inclination with respect to the loading direction on yield stress, the comparison of the data and model predictions shows that a random distribution of habit planes fits the flow response. It is further inferred that the tension-compression asymmetry arises from the non-Schmid effects.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of the scanning strategy on the formation of residual stresses in additively manufactured Ti-6Al-4V

During the laser-powder bed fusion (L-PBF) process, high laser intensities, short interaction times and highly localized heat input drive large thermal gradients that result in a state of high residual stresses. Generally, the residual stresses that develop during the L-PBF process can compromise the performance of the component. Up to now, the literature has indicated that the magnitude of the residual stresses can be affected by various process parameters. In this study, all process parameters such as laser power and speed are held fixed and the focus is solely on the effect of the laser scan strategy on the three-dimensional residual stress state of L-PBF metallic components. Four Ti-6Al-4V bridge shaped components were built using island and continuous scanning patterns parallel and offset 45° from the sample axes. High-energy X-ray diffraction was used to determine the residual stress field in each of the components. Two of them were re-measured after being partially removed from the build plate. The assumptions implicit in diffraction measurements of stress are reviewed and discussed in depth because the unique microstructure associated with L-PBF Ti-6Al-4V renders the validity of those assumptions uncertain. Specifically, additional data was collected and analyzed to evaluate the relationship between grain scale and macroscopic scale stresses. The observed residual stresses were large, ½ to ¾ of the yield strength, particularly the build direction stresses near the lateral edges of the bridges. Here in this work, the higher stresses were observed in the bridges built via the island scan strategies, chiefly near the edges of the parts.

36 MATERIALS SCIENCE↗