A study of the microstructures and mechanical properties of Ti6Al4V fabricated by SLM under vacuum

Zhou, Bin; Zhou, Jun; Li, Hongxin; Feng, Lin

doi:10.1016/j.msea.2018.03.021

Cited by 108 publications

(45 citation statements)

References 27 publications

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“…An artifact of the applied particle segmentation was the segmentation of truly sintered particles. However, this oversegmentation affects only a small portion of particles as it can be observed by means of optical microscopy of LBM powder [7,33,34]. The amount of false particle segmentation should be vanishing within the statistics of the analyzed number of particles (70,000 for steel 316L and 50,000 for Ti-6Al-4V).…”

Section: Particle Sizementioning

confidence: 98%

3D Shape Analysis of Powder for Laser Beam Melting by Synchrotron X-ray CT

Thiede

Mishurova

Evsevleev

et al. 2019

QuBS

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The quality of components made by laser beam melting (LBM) additive manufacturing is naturally influenced by the quality of the powder bed. A packing density <1 and porosity inside the powder particles lead to intrinsic voids in the powder bed. Since the packing density is determined by the particle size and shape distribution, the determination of these properties is of significant interest to assess the printing process. In this work, the size and shape distribution, the amount of the particle’s intrinsic porosity, as well as the packing density of micrometric powder used for LBM, have been investigated by means of synchrotron X-ray computed tomography (CT). Two different powder batches were investigated: Ti–6Al–4V produced by plasma atomization and stainless steel 316L produced by gas atomization. Plasma atomization particles were observed to be more spherical in terms of the mean anisotropy compared to particles produced by gas atomization. The two kinds of particles were comparable in size according to the equivalent diameter. The packing density was lower (i.e., the powder bed contained more voids in between particles) for the Ti–6Al–4V particles. The comparison of the tomographic results with laser diffraction, as another particle size measurement technique, proved to be in agreement.

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Section: Particle Sizementioning

confidence: 98%

3D Shape Analysis of Powder for Laser Beam Melting by Synchrotron X-ray CT

Thiede

Mishurova

Evsevleev

et al. 2019

QuBS

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“…PH stainless-steel AM samples exhibit columnar bcc grains with strong overall [118] texture and small equi-axed fcc grains at molten pool boundaries, as shown in Figure 4. Previous work on as-built PH SS AM components revealed a non-equilibrium microstructure, as well as strong differences in texture parallel and perpendicular to the build direction, due to the very high cooling rates [17,99,[104][105][106][107]115]. Some of the literature claimed that the as-built microstructure via L-PBF contains martensite and retained austenite (metastable phase at room temperature) [26,27,95,98,[119][120][121][122], completely different from that of a wrought 17-4 PH stainless steel, which is fully martensitic.…”

Section: Microstructure In As L-pbfed Statementioning

confidence: 99%

“…In terms of cost and production cycle, significant savings in raw materials and total lead time can be achieved [105]. In terms of performance, the strength of the L-PBF part is often superior to casting and comparable to wrought parts [106,107]. The weldability and the austenitic/martensitic microstructure of PH stainless steels make it an attractive alloy for additive manufacturing (AM) processing [108].…”

mentioning

confidence: 99%

Laser Powder Bed Fusion of Precipitation-Hardened Martensitic Stainless Steels: A Review

Zai

Zhang

Wang

et al. 2020

Metals

100

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Martensitic stainless steels are widely used in industries due to their high strength and good corrosion resistance performance. Precipitation-hardened (PH) martensitic stainless steels feature very high strength compared with other stainless steels, around 3-4 times the strength of austenitic stainless steels such as 304 and 316. However, the poor workability due to the high strength and hardness induced by precipitation hardening limits the extensive utilization of PH stainless steels as structural components of complex shapes. Laser powder bed fusion (L-PBF) is an attractive additive manufacturing technology, which not only exhibits the advantages of producing complex and precise parts with a short lead time, but also avoids or reduces the subsequent machining process. In this review, the microstructures of martensitic stainless steels in the as-built state, as well as the effects of process parameters, building atmosphere, and heat treatments on the microstructures, are reviewed. Then, the characteristics of defects in the as-built state and the causes are specifically analyzed. Afterward, the effect of process parameters and heat treatment conditions on mechanical properties are summarized and reviewed. Finally, the remaining issues and suggestions on future research on L-PBF of martensitic precipitation-hardened stainless steels are put forward.Metals 2020, 10, 255 2 of 25 types of microstructures can be obtained with different heat treatment processes [9]. The typical temperature range for aging heat treatment for this alloy is 480-620 • C [1]. Under the H900 condition (aging temperature: 482 • C, time: 1 h), the precipitation in 17-4 PH stainless steel begins with Cu-rich precipitates (bcc, body center cubic) that maintain a coherent relationship with the matrix, which would lead to an increase in tensile strength and toughness [4]. These precipitates can transform into non-coherent Cu-rich particles (fcc, face center cubic) after extended aging at 400 • C [5]. After experiencing over-aging, the precipitates are coarsened. The number of precipitates is reduced, and the coherence relationship is also destroyed [6,10]. These changes together lead to a decrease in mechanical strength, but an increase in ductility and impact toughness.PH stainless steels are widely used in the aerospace industry [11,12], the marine industry [13], nuclear reactor components [14], chemical process equipment [15], and medical apparatus due to their high tensile strength, impact strength, fracture toughness, and corrosion resistance at typical service temperatures below 300 • C [15,16]. Most of these parts are important load-bearing components of heavy machinery in a demanding service environment. However, PH stainless steels have poor workability and machinability due to their high strength and high hardness, which result in a long production cycle and difficulties in obtaining desired shapes through conventional machining and forming processes [17].Due to the high strength and high hardness of PH steels, they are difficult to b...

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“…For SLM, the bulk energy density E was shown to be associated with the formation of fine acicular martensite and with the lamellar α phase [23]. Partial melting of the pool and a more uniform temperature inside the molten pool will occur if the energy density E is too low (less than 533 J/mm 3 ), leading to a more equiaxed microstructure.…”

Section: • Microstructuresmentioning

confidence: 99%

Variations in the Surface Integrity of Ti-6Al-4V by Combinations of Additive and Subtractive Manufacturing Processes

et al. 2020

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Additive manufacturing (AM) has recently been accorded considerable interest by manufacturers. Many manufacturing industries, amongst others in the aerospace sector, are already using AM parts or are investing in such manufacturing methods. Important material properties, such as microstructures, residual stress, and surface topography, can be affected by AM processes. In addition, a subtractive manufacturing (SM) process, such as machining, is required for finishing certain parts when accurate tolerances are required. This finish machining will subsequently affect the surface integrity and topography of the material. In this research work, we focused on the surface integrity of Ti-6Al-4V parts manufactured using three different types of AM and finished using an SM step. The aim of this study was to gain an understanding on how each process affects the resulting surface integrity of the material. It was found that each AM process affects the materials’ properties differently and that clear differences exist compared to a reference material manufactured using conventional methods. The newly generated surface was investigated after the SM step and each combination of AM/SM resulted in differences in surface integrity. It was found that different AM processes result in different microstructures which in turn affect surface integrity after the SM process.

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A study of the microstructures and mechanical properties of Ti6Al4V fabricated by SLM under vacuum

Cited by 108 publications

References 27 publications

3D Shape Analysis of Powder for Laser Beam Melting by Synchrotron X-ray CT

3D Shape Analysis of Powder for Laser Beam Melting by Synchrotron X-ray CT

Laser Powder Bed Fusion of Precipitation-Hardened Martensitic Stainless Steels: A Review

Variations in the Surface Integrity of Ti-6Al-4V by Combinations of Additive and Subtractive Manufacturing Processes

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