Ti-6Al-4V

The effects of the two support structures, thin-wall tooth contact (TC) and solid-gap (SG), on the Ti-6Al-4V parts fabricated by powder bed fusion electron beam additive manufacturing were investigated. In the Y-plane of the overhang, equiaxed β′ microstructure formed initially and gradually grew into a wider columnar structure with its width about 3 times of that iRn the solid section. Fine α/α′ and β phases were identified within the β′ grains, in which the content of α′ increases from the bottom to the top of the part and α/α′ phase presents strong textures of 0001 and 112¯0 parallel to the build-direction. In addition, more defects were observed in the overhang than the solid, especially at the interface between the solid and the overhang sections which also induced the stress concentration. Compressive residual stresses were revealed in the parts with some points showing minor tensile residual stresses. Compared to the SG part, the TC part had a lower Vickers hardness. The solid part under the SG part acted as a heat sink and enhanced heat dissipation during the manufacturing process, which affected the thermal gradient and improved the microstructures and mechanical properties in the overhang. The teeth in the TC part did limit the occurrence of the wrapping phenomenon. Taking advantages of the two designs, a new support design, SG support with teeth at the tip-end of overhang, is recommended.

In recent years; additive manufacturing technologies has become widely used in aviation and biomedical sectors as it allows the production of complex parts with less waste materials. Additive manufacturing of titanium alloys; which are currently widely used because of the advantages they provide in these sectors, has been an important research subject. The production of Ti-6Al-4V allloy, which is used in structural parts in the aviation sector and prostheses in the biomedical sector, with additive manufacturing technologies is rapidly increasing. In this study; the usage areas of titanium parts, the production of titanium powders, different additive manufacturing technologies used in the production of titanium parts, comparsion of these technologies with conventional techniques and the effects of post treatments on titanium additive manufactured parts have been investigated.

X. Wang, X. Gong, K. Chou, Review on powder-bed laser additive manufacturing of Inconel 718 parts, Proc. Inst. Mech. Eng. Part B J. Eng. Manuf. 231 (2017) 1890–1903. doi:10.1177/0954405415619883.

http://journals.sagepub.com/doi/abs/10.1177/0954405415619883?journalCode=pibb

This study presents a thorough literature review on the powder-bed laser additive manufacturing processes such as selective laser melting of Inconel 718 parts. This article first introduces the general aspects of powder-bed laser additive manufacturing and then discusses the unique characteristics and advantages of selective laser melting. The bulk of this study includes extensive discussions of microstructures and mechanical properties, together with the application ranges of Inconel 718 parts fabricated by selective laser melting.

Electron Beam Additive Manufacturing (EBAM) has a lot of advantages and has become an attractive manufacturing method to produce the Ti-6Al-4V alloy. In this study, four Ti-6Al-4V rectangular blocks were manufactured by the EBAM process with four different beam scanning speeds (Speed Function x-SF20, SF36, SF50, and SF65). Based on the experimental results, the beam scanning speed did show notable effects on the preferred orientation of the a phase in the Z-plane which presents a relatively strong < 2 1 1 4 > and < 1 0 1 0 > texture. However, with the increase of the beam speed, the intensity of the texture in the Z-plane decreases first and then increases. For the Y-plane, the preferred orientation direction of a changes from < 2 1 1 1 > (SF20), < 0 0 0 1 > (SF36, SF50) to < 1 0 1 2 > (SF65) with their maximum intensity decreased from 13.58 to 8.85 times of the random intensity. Generally, the parts did not show outstanding anisotropic characteristics in hardness and elastic modulus. The SF50 sample presents the highest properties (Vickers hardness and elastic modulus) between the four parts, which results from its finest microstructure and the weakest texture.

X. Wang, T. Keya, K. Chou, Build Height Effect on the Inconel 718 Parts Fabricated by Selective Laser Melting, Procedia Manuf. 5 (2016) 1006–1017.
doi:http://dx.doi.org/10.1016/j.promfg.2016.08.089.

Selective laser melting (SLM) is an emerging metal additive manufacturing (AM) technology. It has been employed in many applications including propulsion components which are made of nickel-based superalloys, such as Inconel 718. In this study, the effect of the build height on the mechanical properties and microstructure of SLM-processed Inconel 718 parts was investigated. The samples were cut from the Inconel 718 build part after stress relief. They were prepared for microstructure observations and nanoindentation testing. The results are summarized as following. Young's modulus and hardness obtained from the nanoindentation tests are comparable with or superior to that from traditional manufacturing methods. In addition, there do not appear significant differences in mechanical properties along the build height of the parts, though the columnar grains of the side-surface specimens are narrower at the bottom layers of the part. Moreover, the texture analysis results imply no significant anisotropic characteristics for the mechanical properties between the scanning surface and the side surface of the build parts.

The microstructure and phase composition in selective laser melted (SLM) Ti-6Al-4V plays a key role for its mechanical performance. The microstructure evolution in SLM Ti-6Al-4V was studied in the as-built condition and after sub-transus heat treatments between 400 C and 800 C focusing on elemental partitioning and the role of lattice defects on precipitation of the b phase. With SLM parameters corresponding to low volume energy density (E V ¼ 77 J/mm 3) the as-built microstructure consisted of acicular martensite and showed a higher density of lattice defects than that synthesized under high E V ¼ 145 J/mm 3 condition. High energy X-ray synchrotron diffraction indicated the presence of ~2 wt.% b-phase at this high E V. Moreover, atom-probe tomography revealed enrichments in b-stabilizers at one-and two-dimensional lattice defects. These fine enriched one-dimensional columnar and two-dimensional features are identified as precursors of b-phase, revealing the role of lattice defects for b-precipitation. Upon annealing at 400 C and 530 C, b-films began to fragment into bÀplatelets and nanoparticles, whereas annealing at 800 C led to a coarse-lamellar a/b-microstructure. Moreover, a 2-Ti 3 Al was found in the 400 C annealed condition. In line with the microstructure changes, Vickers hardness increased upon annealing at temperatures up to 530 C and dropped when coarsening occurred at higher temperatures. Substantial element partitioning occurred during thermally driven martensite decomposition, which was significantly stronger for Fe than for V.

Material removal process for dies, moulds and additionally diverse aircraft parts can be made possible by the high-speed end milling operation. Devious cutting forces are created by the impact of various cutting parameters in course with high speed milling process. Due to this phenomenon the wear and chatter of tool can occur. Cutting force prediction is useful method to reduce the chatter occurrence during the machining of hardest materials. DEFORM 3D is an important simulation software which is used for the analysis of complicated metal removal processes. In this work, the tool insert was designed by Solid Works modelling software. The FEM simulation of high-speed end milling of Titanium-Vanadium based alloy was carried out in Deform 3D simulation software to obtain the cutting forces. The material behaviour was modelled with a classical constitutive material equation and was applied in the FEM code to predict the effective stress, strain, temperature and cutting forces towards the impact of cutting parameters. Analysis of variance is achieved to determine the impact of cutting forces with help of Taguchi method in Minitab-17. L16 orthogonal array was used to conduct the analysis of high speed end milling.

Ti-6Al-4V is classified among the most commonly used Ti-alloys and is extensively used in aerospace and medical industries where low-density, high strength and outstanding corrosion resistance are required.
This material cannot be processed by conventional machining methods because of its high strength. Abrasive Waterjet Machining, abbreviated as AWJM, is an unconventional machining process suitable for machining Ti-6Al-4V as it generates less heat affected zone. The quality of AWJM is governed by process parameters, the selection of these parameters is critical in this technology to achieve the desirable output measures. This paper provides an experimental investigation for the performance analysis of process parameters on machining Ti-6Al-4V using abrasive waterjet technology. In order to select appropriate parameters, a mathematical equations were developed using Regression Investigation Method (RIM) Artificial Neural Network (ANN) procedures. Based on the input and output data collected from the experiments, modelling is done and tested for the different set of data to ensure the accuracy. These mathematical models can be used to identify the static and dynamic behavior of the process. These models will further help in simulating the process, expanding the design facilities and studying the physical and chemical variation in the process. Models provide understanding the operations, control methods and the possible optimization. The developed models also help in documenting the performance of the existing system.

In this study, mechanical properties in Ti-6Al-4V samples built with the powder-bed electron beam additive manufacturing (EBAM) process over a range of beam scanning speeds were experimentally investigated. Four levels of speed functions were applied to build samples, which were used to prepare the specimens for the nanoindentation test to obtain their mechanical properties. The measured averaged Young's modulus and hardness are about 111.7~119.0 GPa and 5.24~6.52 GPa, respectively. It has been found that the Young's modulus and hardness increase with the increase of scanning speed in EBAM. The scanning surface presents more superior mechanical properties than those from side surface. The mechanical properties are also correlated to the microstructure characterization of EBAM components.

Different energy densities in Selective Laser Melting produce different metallurgical properties of the product surface, which include adhered powder particles, waviness, porosity, and microstructure. In this research, the corrosion behavior of these structural properties was investigated and compared with heat-treated samples. The size and arrays of α'-martensitic varied significantly due to the effects of different cooling rates and the number of effective thermal cycles caused by different scanning speeds and energy densities. The surface particles experienced different thermal effects that significantly changed their microstructure with each other and with respect to the main surface, which remarkably affected the corrosion properties. The densities, hardness, and tensile properties of the samples were also presented and interpreted their relations with corrosion. These correlations between the metallurgical and corrosion properties of SLM products support biomedical engineers in the further development of bespoke medical devices, especially implants.

The effects of gas nitriding have been studied for Ti-6Al-4V alloy at different time and temperatures. Gas nitriding was performed from 600°C to 1200°C for the duration of 4 to 8 hours using Dilatometer. The surface roughness values were compared to get insight into the surface morphology. Sample appearance after nitriding was different from the base metal, and color demonstrated variation with time and temperature. After nitriding the basic metallic silver color was converted into blue, golden and gray. At lower temperatures, blue and golden color was common and as temperature increased the color changed to grayish. Initially at lower temperatures (i.e. 600°C and 700°C), titanium alloy's silver metallic color turned into blue/golden, and the intensity of this color was increased with the increase in temperature and time of nitriding. Moreover, above beta transus temperature (i.e. 1000°C, 1100°C and 1200°C), the material appeared to be gray. The hardness after nitriding was increased with increase in nitriding layer thickness. The maximum hardness value HV 0.5 was reported to be 1735. Surface images were taken by Scanning Electron Microscopy (SEM), and these images revealed that the formation of nitrides was started from the grain boundaries.

This proposed work is to improve the strength and wear resistance of materials by reinforcing the composite preform (Ti-6Al-4V) with an addition of (2-10) wt. % of nano boron carbide particles. The characterization was performed through Scanning electron microscope of above composites. While measuring wear using pin-on-disk testing machine, the temperature, load, sliding distance are varied for identifying the nature of dry and high temperature wear of prepared composite.
The output of this wear experimental work is fed to the soft computing based tool like Artificial Neural Network for predicting the wear properties such as specific wear rate and coefficient of friction. Further, with respect to the temperature and B4 C%, the wear properties are analysed using data mining tool like Decision Tree. Moreover, fixing the range of metal powders for classifying the wear properties of composite preforms can be automated by using Fuzzy logic.

Self-organized TiO2 nanotubular arrays were fabricated by electrochemical anodization of Ti-6Al-4V plates in an NH4F/H3PO4 electrolyte. The effect of microstructural evolutions on the wettability and tribological behavior of the TiO2 nanotubes was investigated. Based on the XRD profiles of the fabricated material, the characteristic TiO2 peaks were not recognized after anodization; however, highly crystalline TiO2 (anatase and rutile) was formed due to crystallization during annealing at 500 degrees C for 1.5 h. The nanotube arrays were converted entirely to rutile at 700 degrees C. From a microstructure point of view, a highly ordered nanotube structure was achieved when the specimen was annealed at 500 degrees C, with a length of 0.72 mu m and a pore diameter of 72 nm. Further increasing the annealing temperature to 700 degrees C resulted in the complete collapse of the tubular structure. The results indicate that the improved wettability of the anodized specimens was due to the combination of the effects of both the surface oxide layer and the increased surface roughness achieved after anodization. Moreover, the wear resistance and wettability of the sample annealed 500 degrees C were improved due to the high hardness (435 HV) and low coefficient of friction (0.133-168) of the highly crystalline structure of the TiO2 nanotubes. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

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