Microstructure-Properties Relationships of Ti-6Al-4V Parts Fabricated by Selective Laser Melting

Mezzetta, Justin; Choi, Jin Nam; Milligan, J.; Danovitch, J.; Chekir, N.; Bois-Brochu, Alexandre; Zhao, Yaoyao Fiona; Brochu, Mathieu

doi:10.1007/s40684-018-0062-1

Cited by 35 publications

(17 citation statements)

References 21 publications

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“…The microstructure of the Ti6Al4V alloy produced by SLM technology is entirely made of the martensitic α’phase [10,21]. This is a result of high rates of heating and cooling of the solidified powder, which are neglected in the DMLS process [22].…”

Section: Introductionmentioning

confidence: 99%

Effect of Laser Energy Density, Internal Porosity and Heat Treatment on Mechanical Behavior of Biomedical Ti6Al4V Alloy Obtained with DMLS Technology

Mierzejewska

2019

Materials

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The purpose of this paper was to determine the influence of selected parameters of Direct Metal Laser Sintering and various heat treatment temperatures on the mechanical properties of Ti6Al4V samples oriented vertically (V, ZX) and horizontally (H, XZ). The performed micro-CT scans of as-build samples revealed that the change in laser energy density significantly influences the change in porosity of the material, which the parameters (130–210 W; 300–1300 mm/s), from 9.31% (130 W, 1300 mm/s) to 0.16% (190 W, 500 mm/s) are given. The mechanical properties, ultimate tensile strength (UTS, Rm) and yield strength (YS, Re) of the DMLS as-build samples, were higher than the ASTM F 1472 standard suggestion (UTS = 1100.13 ± 126.17 MPa, YS = 1065.46 ± 127.91 MPa), and simultaneously, the elongation at break was lower than required for biomedical implants (A = 4.23 ± 1.24%). The low ductility and high UTS were caused by a specific microstructure made of α’ martensite and columnar prior β grains. X-Ray Diffraction (XRD) analysis revealed that heat treatment at 850 °C for 2 h caused the change of the microstructure intothe α + β combination, affecting the change of strength parameters—a reduction of UTS and YS with the simultaneous increase in elongation (A). Thus, properties similar to those indicated by the standard were obtained (UTS = 908.63 ± 119.49 MPa, YS = 795.9 ± 159.32 MPa, A = 8.72 ± 2.51%), while the porosity remained almost unchanged. Moreover, the heat treatment at 850 °C resulted in the disappearance of anisotropic material properties caused by the layered structure (UTSZX = 908.36 ± 122.79 MPa, UTSXZ = 908.97 ± 118.198 MPa, YSZX = 807.83 ± 124.05 MPa, YSXZ = 810.56 ± 124.05 MPa, AZX = 8.75 ± 2.65%, and AXZ = 8.68 ± 2.41%).

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Section: Introductionmentioning

confidence: 99%

Effect of Laser Energy Density, Internal Porosity and Heat Treatment on Mechanical Behavior of Biomedical Ti6Al4V Alloy Obtained with DMLS Technology

Mierzejewska

2019

Materials

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“…Appreciable advances have recently been made in the fabrication of metal components for applications requiring strict tolerances and high-load capacity [ 1 ]. Success in this area can largely be attributed to the improvements of the powder properties, such as composite structures or engaged nano-particles, in the developed metallic powders to facilitate direct/selective laser melting methods [ 2 , 3 ]. Notable advances have also been made in the development of scanning strategies [ 4 ] and the associated integration with finite element method-based numerical models for the in-process control in the melting process [ 5 ].…”

Section: Introductionmentioning

confidence: 99%

Effects of Energy Parameters on Dimensional Accuracy When Joining Stainless-Steel Powders with Heterogeneous Metal Substrates

2021

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This work presents some breakthroughs for obtaining high dimensional accuracy and reliable geometrical tolerance in the joining of stainless-steel powders with heterogeneous substrates. In the laser melting process, the interfacial energy fractions and forces acting at the solid–liquid surface of the melting powders can effectively vary their geometrical shapes and positions before they turn into the liquid phase. When the interfacial free energy is low, the melting powders are near molten, thus the successive volumetric changes can alter the layered geometry and positions. This assumption was validated by a powder-bedding additive manufacturing process to consolidate stainless-steel 316L powders (SLM 316L) on a thin heterogeneous stainless-steel substrate. Experiments were carried out to reveal the effects of the process parameters, such as laser power (100–200 W), exposure duration (50–100 µs) and point distance (35–70 µm) on the resulting material density and porosity and the corresponding dimensional variations. A fractional factorial design of experiment was proposed and the results of which were analyzed statistically using analysis of variances (ANOVA) to identify the influence of each operating factor. High energy densities are required to achieve materials of high density (7.71 g/cm3) or low porosity (3.15%), whereas low energy densities are preferable when the objective is dimensional accuracy (0.016 mm). Thermally induced deflections (~0.108 mm) in the heterogeneous metal substrate were analyzed using curvature plots. Thermally induced deformations can be attributed to volumetric energy density, scanning strategy, and the lay-up orientation. The parametric optimizations for increasing in dimensional accuracy (Z1: ~0.105 mm), or in material density (~7.71 g/cm3) were proven with high conversion rates of 88.2% and 96.4%, respectively, in validation runs.

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“…Titanium Grade 5 (Ti-6Al-4V) accounts for the largest part of the world's titanium production due to the favourable combination of strength-to-weight ratio, good heat treatability and relatively high service temperatures. The material is very well-known from conventional manufacturing, however the unique thermal input from the SLM process results in the formation of non-equilibrium microstructures [6]. The local melting of the powder in the SLM process combined with the rapid movement of the laser results in steep temperature gradients and the formation of martensitic α' phase inside elongated prior-β grains [3,4].…”

Section: Introductionmentioning

confidence: 99%

“…The local melting of the powder in the SLM process combined with the rapid movement of the laser results in steep temperature gradients and the formation of martensitic α' phase inside elongated prior-β grains [3,4]. This martensitic microstructure in printed parts has been shown to have a higher strength than in conventional Ti-6Al-4V, albeit much more brittle [4,5,6]. In most research, the ductility falls short of the 10 % requirement stipulated in ASTM F2924 standard for additive manufacturing of Ti-6Al-4V [7] and a heat treatment is necessary for improving the mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

“…SLM is a layer-based manufacturing process, which makes it necessary to consider also the build direction. Mezzetta et al [6] found that tensile specimens printed in lying configuration have the lowest ductility and highest strength, as opposed to printing tensile specimens in standing geometry, which show the opposite relationship. Simonelli et al [8] found that flat tensile bars lying on their side show improved ductility and strength.…”

Section: Introductionmentioning

confidence: 99%

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The influence of microstructure on mechanical properties of SLM 3D printed Ti-6Al-4V

et al. 2020

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This research focuses on establishing the relationship between the SLM process parameters, microstructure and mechanical properties in 3D printed ti-6Al-4V. To this end modelling of the thermal history, reflecting the applied process parameters, is linked to the as-printed microstructure, which, in turn, is linked to experimentally determined mechanical properties. The very high cooling rates in the centre of the specimen, as predicted by modelling, lead to a fine, martensitic microstructure, while the slower cooling rates close to the support structure lead to a fine lamellar α+β microstructure. The tensile properties, in particular the ductility, were found to depend on the printing orientation and surface finish.

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Microstructure-Properties Relationships of Ti-6Al-4V Parts Fabricated by Selective Laser Melting

Cited by 35 publications

References 21 publications

Effect of Laser Energy Density, Internal Porosity and Heat Treatment on Mechanical Behavior of Biomedical Ti6Al4V Alloy Obtained with DMLS Technology

Effect of Laser Energy Density, Internal Porosity and Heat Treatment on Mechanical Behavior of Biomedical Ti6Al4V Alloy Obtained with DMLS Technology

Effects of Energy Parameters on Dimensional Accuracy When Joining Stainless-Steel Powders with Heterogeneous Metal Substrates

The influence of microstructure on mechanical properties of SLM 3D printed Ti-6Al-4V

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