Preheating of Selective Laser Melted Ti6Al4V: Microstructure and Mechanical Properties

Vrancken, Bey; Buls, Sam; Kruth, Jean‐Pierre; Humbeeck, Jan Van

doi:10.1002/9781119296126.ch215

Cited by 19 publications

(21 citation statements)

References 17 publications

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“…On the other hand, the regular microhardness values obtained for the IHT-affected microstructure along the building direction (~420 ± 10 HV 0.2, as shown in Figure 3 ), are comparable to those reported for fine lamellar α + β microstructures (~439 ± 5 HV 0.5) formed during high-temperature SLM fabrication of the Ti-64 alloy [ 13 ].…”

Section: Discussionsupporting

confidence: 80%

“…Previous investigations reported that α’ → α + β martensite decomposition—leading to configurations of α and β phases that render acceptable mechanical performance—can be induced during SLM via intrinsic heat treatment (IHT) by alteration of processing parameters including energy density and temperature of the building platform (e.g., [ 10 , 11 ]). However, modifications of these parameters can also imply the formation of void defects (i.e., round or crack-like pores) and a decrease in the ductility of the alloy via excessive oxygen pick up [ 12 , 13 ]. Thus, exploration of alternative laser scanning strategies based on a compromise between microstructure design and minimization of bulk defects is required to improve the SLM manufacturability of Ti-64.…”

Section: Introductionmentioning

confidence: 99%

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Inducing Stable α + β Microstructures during Selective Laser Melting of Ti-6Al-4V Using Intensified Intrinsic Heat Treatments

et al. 2017

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Selective laser melting is a promising powder-bed-based additive manufacturing technique for titanium alloys: near net-shaped metallic components can be produced with high resource-efficiency and cost savings. For the most commercialized titanium alloy, namely Ti-6Al-4V, the complicated thermal profile of selective laser melting manufacturing (sharp cycles of steep heating and cooling rates) usually hinders manufacturing of components in a one-step process owing to the formation of brittle martensitic microstructures unsuitable for structural applications. In this work, an intensified intrinsic heat treatment is applied during selective laser melting of Ti-6Al-4V powder using a scanning strategy that combines porosity-optimized processing with a very tight hatch distance. Extensive martensite decomposition providing a uniform, fine lamellar α + β microstructure is obtained along the building direction. Moreover, structural evidence of the formation of the intermetallic α2-Ti3Al phase is provided. Variations in the lattice parameter of β serve as an indicator of the microstructural degree of stabilization. Interconnected 3D networks of β are generated in regions highly affected by the intensified intrinsic heat treatment applied. The results obtained reflect a contribution towards simultaneous selective laser melting-manufacturing and heat treatment for fabrication of Ti-6Al-4V parts.

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Section: Discussionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Inducing Stable α + β Microstructures during Selective Laser Melting of Ti-6Al-4V Using Intensified Intrinsic Heat Treatments

et al. 2017

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“…Phase transformations can be induced by heat treatments leading to a more ductile microstructure consisting of stable α (hcp) and β (bcc) phases. Commonly, the heat treatment is conducted after the building process (“extrinsic” or “ex-situ” after the AM process) (e.g., [ 10 , 11 , 12 , 13 ]), but approaches of in-situ heat treatment by preheating the baseplate or build space also exist [ 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

An Assessment of Subsurface Residual Stress Analysis in SLM Ti-6Al-4V

et al. 2017

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Ti-6Al-4V bridges were additively fabricated by selective laser melting (SLM) under different scanning speed conditions, to compare the effect of process energy density on the residual stress state. Subsurface lattice strain characterization was conducted by means of synchrotron diffraction in energy dispersive mode. High tensile strain gradients were found at the frontal surface for samples in an as-built condition. The geometry of the samples promotes increasing strains towards the pillar of the bridges. We observed that the higher the laser energy density during fabrication, the lower the lattice strains. A relief of lattice strains takes place after heat treatment.

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“…Substrate preheating is an effective method for reducing the thermal stress in the SLM process and altering the microstructure by decreasing the thermal gradient [ 43 , 44 ]. To investigate the effect of preheating on the microstructure evolution, in the present IN718 specimens, a further simulation was performed in which the initial substrate temperature was set at a constant 400 °C.…”

Section: Resultsmentioning

confidence: 99%

Prediction of Epitaxial Grain Growth in Single-Track Laser Melting of IN718 Using Integrated Finite Element and Cellular Automaton Approach

Dezfoli

Raza

2021

Materials

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The mechanical properties of selective laser melting (SLM) components are fundamentally dependent on their microstructure. Accordingly, the present study proposes an integrated simulation framework consisting of a three-dimensional (3D) finite element model and a cellular automaton model for predicting the epitaxial grain growth mode in the single-track SLM processing of IN718. The laser beam scattering effect, melt surface evolution, powder volume shrinkage, bulk heterogeneous nucleation, epitaxial growth, and initial microstructure of the substrate are considered. The simulation results show that during single-track SLM processing, coarse epitaxial grains are formed at the melt–substrate interface, while fine grains grow at the melt–powder interface with a density determined by the intensity of the heat input. During the solidification stage, the epitaxial grains and bulk nucleated grains grow toward the top surface of the melt pool along the temperature gradient vectors. The rate of the epitaxial grain growth varies as a function of the orientation and size of the partially melted grains at the melt–substrate boundary, the melt pool size, and the temperature gradient. This is observed that by increasing heat input from 250 J/m to 500 J/m, the average grain size increases by ~20%. In addition, the average grain size reduces by 17% when the initial substrate grain size decreases by 50%. In general, the results show that the microstructure of the processed IN718 alloy can be controlled by adjusting the heat input, preheating conditions, and initial substrate grain size.

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Preheating of Selective Laser Melted Ti6Al4V: Microstructure and Mechanical Properties

Cited by 19 publications

References 17 publications

Inducing Stable α + β Microstructures during Selective Laser Melting of Ti-6Al-4V Using Intensified Intrinsic Heat Treatments

Inducing Stable α + β Microstructures during Selective Laser Melting of Ti-6Al-4V Using Intensified Intrinsic Heat Treatments

An Assessment of Subsurface Residual Stress Analysis in SLM Ti-6Al-4V

Prediction of Epitaxial Grain Growth in Single-Track Laser Melting of IN718 Using Integrated Finite Element and Cellular Automaton Approach

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