Microstructures and Hardness Properties for β-Phase Ti–24Nb–4Zr–7.9Sn Alloy Fabricated by Electron Beam Melting

Additively-manufactured Ti-6Al-4V (Ti64) exhibits high strength but in some cases inferior elongation to those of conventionally manufactured materials. Post-processing of additively manufactured Ti64 components is investigated to modify the mechanical properties for specific applications while still utilizing the benefits of the additive manufacturing process. The mechanical properties and fatigue resistance of Ti64 samples made by electron beam melting were tested in the as-built state. Several heat treatments (up to 1000 °C) were performed to study their effect on the microstructure and mechanical properties. Phase content during heating was tested with high reliability by neutron diffraction at Los Alamos National Laboratory. Two different hot isostatic pressings (HIP) cycles were tested, one at low temperature (780 °C), the other is at the standard temperature (920 °C). The results show that lowering the HIP holding temperature retains the fine microstructure (~1% β phase) and the 0.2% proof stress of the as-built samples (1038 MPa), but gives rise to higher elongation (~14%) and better fatigue life. The material subjected to a higher HIP temperature had a coarser microstructure, more residual β phase (~2% difference), displayed slightly lower Vickers hardness (~15 HV10N), 0.2% proof stress (~60 MPa) and ultimate stresses (~40 MPa) than the material HIP’ed at 780 °C, but had superior elongation (~6%) and fatigue resistance. Heat treatment at 1000 °C entirely altered the microstructure (~7% β phase), yield elongation of 13.7% but decrease the 0.2% proof-stress to 927 MPa. The results of the HIP at 780 °C imply it would be beneficial to lower the standard ASTM HIP temperature for Ti6Al4V additively manufactured by electron beam melting.

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Hot deformation behavior and flow stress modeling of Ti–6Al–4V alloy produced via electron beam melting additive manufacturing technology in single β-phase field

Materials Science and Engineering A ◽

10.1016/j.msea.2020.139822 ◽

2020 ◽

Vol 792 ◽

pp. 139822 ◽

Cited By ~ 3

Author(s):

Abdollah Saboori ◽

Ata Abdi ◽

Seyed Ali Fatemi ◽

Giulio Marchese ◽

Sara Biamino ◽

...

Keyword(s):

Electron Beam ◽

Additive Manufacturing ◽

Flow Stress ◽

Phase Field ◽

Hot Deformation ◽

Deformation Behavior ◽

Electron Beam Melting ◽

Hot Deformation Behavior ◽

Additive Manufacturing Technology ◽

Β Phase

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Effect of Hot Isostatic Pressing on Microstructures and Mechanical Properties of Ti6Al4V Fabricated by Electron Beam Melting

Metals ◽

10.3390/met10050593 ◽

2020 ◽

Vol 10 (5) ◽

pp. 593

Author(s):

Changyong Liu ◽

Zhuokeng Mai ◽

Deng Yan ◽

Mingguang Jiang ◽

Yuhong Dai ◽

...

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Grain Size ◽

Electron Beam ◽

Electron Beam Melting ◽

Hot Isostatic Pressing ◽

Phase Ratio ◽

Lamellar Thickness ◽

Isostatic Pressing ◽

Β Phase

This study investigated the effects of hot isostatic pressing (HIP) on the microstructures and mechanical properties of Ti6Al4V fabricated by electron beam melting (EBM). The differences of surface morphologies, internal defects, relative density, microstructures, textures, mechanical properties and tensile fracture between the as-built and HIPed samples were observed using various characterization methods including optical metallography microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) and tensile tests. It was found that the main effects of HIP on microstructures include—the increase of average grain size from 7.96 ± 1.21 μm to 11.34 ± 1.89 μm, the increase of α lamellar thickness from 0.71 ± 0.15 μm to 2.49 ± 1.29 μm and the increase of β phase ratio from 4.7% to 10.5% in terms of area fraction on the transversal section. The combinatorial effects including densification, increase of grain size, α lamellar thickness, β phase ratio, reduction of dislocation density and transformation of dislocation patterns contributed to the improvement of elongation and ductility of EBM-fabricated Ti6Al4V. Meanwhile, these effects also resulted in a slight reduction of the yield strength and UTS mainly due to the coarsening effect of HIP.

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Correction to: Post-processing to Modify the α Phase Micro-Texture and β Phase Grain Morphology in Ti-6Al-4V Fabricated by Powder Bed Electron Beam Melting

Metallurgical and Materials Transactions A ◽

10.1007/s11661-019-05300-2 ◽

2019 ◽

Vol 50 (8) ◽

pp. 3973-3974

Author(s):

Peeyush Nandwana ◽

Yousub Lee ◽

Chasen Ranger ◽

Anthony D. Rollett ◽

Ryan R. Dehoff ◽

...

Keyword(s):

Electron Beam ◽

Electron Beam Melting ◽

Grain Morphology ◽

Post Processing ◽

Powder Bed ◽

Β Phase ◽

Α Phase

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Residual Lattice Strain and Phase Distribution in Ti-6Al-4V Produced by Electron Beam Melting

Materials ◽

10.3390/ma12040667 ◽

2019 ◽

Vol 12 (4) ◽

pp. 667 ◽

Cited By ~ 9

Author(s):

Tuerdi Maimaitiyili ◽

Robin Woracek ◽

Magnus Neikter ◽

Mirko Boin ◽

Robert Wimpory ◽

...

Keyword(s):

Residual Stress ◽

Electron Beam ◽

Electron Beam Melting ◽

Phase Distribution ◽

High Energy ◽

Process Parameter ◽

Electron Backscattered Diffraction ◽

X Ray ◽

Β Phase ◽

Residual Strains

Residual stress/strain and microstructure used in additively manufactured material are strongly dependent on process parameter combination. With the aim to better understand and correlate process parameters used in electron beam melting (EBM) of Ti-6Al-4V with resulting phase distributions and residual stress/strains, extensive experimental work has been performed. A large number of polycrystalline Ti-6Al-4V specimens were produced with different optimized EBM process parameter combinations. These specimens were post-sequentially studied by using high-energy X-ray and neutron diffraction. In addition, visible light microscopy, scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) studies were performed and linked to the other findings. Results show that the influence of scan speed and offset focus on resulting residual strain in a fully dense sample was not significant. In contrast to some previous literature, a uniform α- and β-Ti phase distribution was found in all investigated specimens. Furthermore, no strong strain variations along the build direction with respect to the deposition were found. The magnitude of strain in α and β phase show some variations both in the build plane and along the build direction, which seemed to correlate with the size of the primary β grains. However, no relation was found between measured residual strains in α and β phase. Large primary β grains and texture appear to have a strong effect on X-ray based stress results with relatively small beam size, therefore it is suggested to use a large beam for representative bulk measurements and also to consider the prior β grain size in experimental planning, as well as for mathematical modelling.

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New Ti–35Nb–7Zr–5Ta Alloy Manufacturing by Electron Beam Melting for Medical Application Followed by High Current Pulsed Electron Beam Treatment

Metals ◽

10.3390/met11071066 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1066

Author(s):

Maria Surmeneva ◽

Irina Grubova ◽

Natalia Glukhova ◽

Dmitriy Khrapov ◽

Andrey Koptyug ◽

...

Keyword(s):

Electron Beam ◽

Electron Beam Melting ◽

Texture Coefficient ◽

Grazing Angle ◽

Surface Finishing ◽

High Current ◽

Tem Analysis ◽

Pulsed Electron Beam ◽

Melted Zone ◽

Β Phase

High-current pulsed electron-beam (PEB) treatment was applied as a surface finishing procedure for Ti–35Nb–7Zr–5Ta (TNZT) alloy produced by electron beam melting (EBM). According to the XRD results the TNZT alloy samples before and after the PEB treatment have shown mainly the single body-centered cubic (bcc) β-phase microstructures. The crystallite size, dislocation density, and microstrain remain unchanged after the PEB treatment. The investigation of the texture coefficient at the different grazing angle revealed the evolution of the crystallite orientations at the re-melted zone formed at the top of the bulk samples after the PEB treatment. The top-view SEM micrographs of the TNZT samples treated by PEB exhibited the bcc β-phase grains with an average size of ~85 μm. TEM analysis of as-manufactured TNZT alloy revealed the presence of the equiaxed β-grains with the fine dispersion of nanocrystalline α and NbTi4 phases together with β-Ti twins. Meanwhile, the β phase regions free of α phase precipitation are observed in the microstructure after the PEB irradiation. Nanoindentation tests revealed that the surface mechanical properties of the melted zone were slightly improved. However, the elastic modulus and microhardness in the heat-affected zone and the deeper regions of the sample were not changed after the treatment. Moreover, the TNZT alloy in the bulk region manufactured by EBM displayed no significant change in the corrosion resistance after the PEB treatment. Hence, it can be concluded that the PEB irradiation is a viable approach to improve the surface topography of EBM-manufactured TNZT alloy, while the most important mechanical parameters remain unchanged.

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Microstructure of Additive Manufactured Ti6Al4V by Electron Beam Melting

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1035.243 ◽

2021 ◽

Vol 1035 ◽

pp. 243-252

Author(s):

Nan Nan Wang ◽

Bao Hong Zhu ◽

De Fu Li ◽

Zhi Shui Yu ◽

Zhong Wen Li ◽

...

Keyword(s):

Electron Beam ◽

Electron Beam Melting ◽

Orthopedic Implants ◽

Columnar Crystal ◽

Repeated Heating ◽

Β Phase ◽

Vacuum Cooling ◽

Bcc Structure ◽

Hcp Structure ◽

Micro Morphology

The electron beam melting-printed Ti6Al4V shows a great potential application for orthopedic implants and aerospace in recent years. A systematic study on the microstructure of additive manufactured Ti6Al4V by electron beam melting both parallel to and perpendicular to the building directions (Z axis) is presented in the present investigation. The results showed that the microstructure of the alloy was α lamina with HCP structure and β bar with BCC structure. The original β phase grew as columnar crystal along the direction of construction, showing an equiaxial shape in the cross section, numerous small α lamellae block the original β phase, and presenting a cluster distribution on the original β grain boundary, and a basket-like distribution in the original β grain. This may be due to the rapid cooling of the small pool after melting, the repeated heating of the subsequent constructed layer on the formed layer, and the subsequent limited vacuum cooling, resulting in the formation of the micro morphology, which leads to the original β grain boundaries broken, and the formation of a distinctive basket or widmanstatten structure [1, 2]. In addition, XRD results indicated that there was α′ martensite, part of which has been decomposes into α phases and β phases, SEM and TEM experiments also proved this. Of note is that random distribution dislocation was observed in TEM. Using EBSD results, and it may be understand that the sample build direction was parallel to [0001] crystal orientation and build plane parallel to (1210) and (1100) crystal facets.

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Post-processing to Modify the α Phase Micro-Texture and β Phase Grain Morphology in Ti-6Al-4V Fabricated by Powder Bed Electron Beam Melting

Metallurgical and Materials Transactions A ◽

10.1007/s11661-019-05247-4 ◽

2019 ◽

Vol 50 (7) ◽

pp. 3429-3439 ◽

Cited By ~ 7

Author(s):

Peeyush Nandwana ◽

Yousub Lee ◽

Chasen Ranger ◽

Anthony D. Rollett ◽

Ryan R. Dehoff ◽

...

Keyword(s):

Electron Beam ◽

Electron Beam Melting ◽

Grain Morphology ◽

Post Processing ◽

Powder Bed ◽

Β Phase ◽

Α Phase

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Microstructures of Electron Beam Melted (EBM) Biomaterial Ti-6Al-4V

MRS Proceedings ◽

10.1557/proc-1132-z09-06 ◽

2008 ◽

Vol 1132 ◽

Cited By ~ 1

Author(s):

Adnan Safdar ◽

Liu-Ying Wei

Keyword(s):

Electron Beam ◽

Electron Beam Melting ◽

Layer Structure ◽

Processing Parameters ◽

Optical Microscope ◽

Solid Samples ◽

Direction Parallel ◽

Β Phase ◽

Shape Structure ◽

Columnar Grains

ABSTRACTTi-6Al-4V alloy is an attractive biomaterial. The current work evaluates the microstructures of the solid and net-shape Ti-6Al-4V alloy produced by Electron Beam Melting (EBM) system using SEM/EDX and optical microscope. The microstructures are influenced by the cooling rate, processing parameters of the EBM system and re-heating of the existing layer during the melting of subsequent layers. Layer structure and columnar grains have been observed, with growing direction parallel to the built direction. The interior of these grains consists of alternating α / β phases. The β phase in the colonies resembles rod shape embedded in the α platelet. Along the grain boundaries more or less continuous α layers were observed. In comparison to solid samples uneven surfaces and pores were seen in the net shape structure. Microhardness evaluation of the EBM produced alloys was also carried out and compared with conventionally produced alloys.

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