Papers by Keyword: Ti-6Al-4V Alloy

Abstract: The surface of Ti6Al4V alloy was rapidly carburized by high-frequency electromagnetic induction heating under vacuum. The microstructure and hardness of the carburized layer were studied. The wear properties of the carburized layer were tested at 50, 100 and 200 rpm using the end face friction and wear device, and the wear mechanism was analyzed. The results show that the TiC strengthening phase was formed on the surface of Ti6Al4V alloy after high-frequency induction carburization, and the surface grains were refined. The surface hardness reaches 1116 HV_0.25, but the brittleness of the carburized layer increases with increasing temperature. The amount of wear was reduced by 54% at 100 rpm. The roughness of the wear scar was reduced from 3.26 μm to 2.28 μm of Ti6A14V alloy matrix. The coefficient of friction and wear rate increases with increasing speed. The wear mechanism was transformed from adhesive wear and oxidative wear of the substrate to abrasive wear after carburizing.

Abstract: The milling experiments were conducted carried out which Ti-6Al-4V alloys with different amount of hydrogen permeating were processed, in order to explore various problem in the machining process of hydrogenated titanium alloy. The main cutting force, microhardness and residual stress before and after milling were measured. The experiments result show that Ti-6Al-4V alloy with appropriate amount of hydrogen can effectively reduce the cutting force, improve the surface hardness and reduce the surface residual stress.

Abstract: In additive manufacturing, technologies based on the fusion of a metallic wire using an electric arc represent an interesting alternative to current manufacturing processes, particularly for large metal parts, thanks to higher deposition rates and lower process costs than powder or wire-laser technologies. A versatile 3D printing device using a DED-W Arc (Direct Energy Deposition by wire-arc) station to melt a metallic filler wire is developed to build titanium parts by optimizing the process parameters and control the geometrical, metallurgical and the mechanical properties of produced parts. In this study, the impact of two different CMT synergic lines on the energetic and geometric behavior of Ti-6Al-4V single deposits is highlighted. These are related to first order parameters: wire feed speed (WFS) and travel speed (TS). The results show difference on energy, geometric of deposits and different deposition regime between these two law with identical process parameters. The second part of this study focuses on the transition from single deposits to walls and blocks. By first choosing the best set of process parameters to make the construction of thin walls (composed of stacked layers), and then the research the optimal horizontal step of deposition (overlapping) for thicker constructions, results obtained made it possible to validate transition from single deposits (1D) to thick walls (3D) without any weld pool collapse or lack of fusion.

Abstract: Additive manufacturing (AM) using wire as an input material is currently in full swing, with very strong growth prospects thanks to the possibility of creating large parts, with high deposition rates, but also a low investment cost compared to the powder bed fusion machines. A versatile 3D printing device using a Direct Energy Deposition Wire-Laser (DED-W Laser) with Precitec Coaxprinter station to melt a metallic filler wire is developed to build titanium parts by optimizing the process parameters. The geometrical and metallurgical of produced parts are analyzed. In the literature, several authors agree to define wire feed speed, travel speed, and laser beam power as first-order process parameters governing laser-wire deposition. This study shows the relative importance of these parameters taking separately as well as the importance of their sequencing at the start of the process. Titanium deposit are obtained with powers never explored in bibliography (up to 5 kW), and wire feed speed up to 5 m.min^-1 with a complete process repeatability.

Abstract: To obtain advanced materials through the development of traditional materials without the addition of another alloying element, advanced heat treatment can be used. One such innovative process is a thermo-hydrogen treatment (THT); it facilitates a purposeful adjustment of an improved microstructure using hydrogen as a temporary alloying element within heat treatment. In this paper, the five-step process of homogenization, hydrogenation, solution treatment, dehydrogenation, and aging was used in THT. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), backscattered electron (BSE), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD) were utilized to analyze the phases and phase transformations in Ti-6Al-4V. Three different homogeneous microstructures were established for the investigation using different homogenization parameters values. The hydrogenation was carried out for these microstructures via hydrogen gas charging leading to hydrogen concentrations for the formation of hydride (δ TiH₂). After the solution treatment at a temperature above β transus temperature (T_β), the metastable phases of a martensitic structure consisting of a mixture of α ́ (hcp) and α ́ ́ (orthorhombic) was found. Steps 4 and 5 of THT were a vacuum annealing (hydrogen degassing) followed by aging treatment. The aging treatment was applied to complete the martensite phase decomposition and the precipitation of two phases. By means of this THT cycle, very fine equiaxed microstructures could be established. These microstructures consist of the α_s phase (secondary α) in the β phase matrix and the α₂ phase (Ti₃Al) in the α_p phase. The precipitation of these phases increases the strength of the Ti-6Al-4V alloy and, consequently, enhances the mechanical properties. No evidence of the δ phase was found.

Abstract: Ti–6Al–4V alloy (Ti64) with different microstructures was first preshocked at ~6–13 GPa and then compression reloaded at 4×10³s^-1 to investigate the effect of microstructure and shock prestrain on the dynamic mechanical behavior of this alloy. The strengthening effect caused by shock prestrain is weaker than that introduced by the uniaxial stress compression during dynamic reloading process regardless of microstructure type and impact stress amplitude. However, the shock-induced enhancement ratio is higher in Ti64 having bimodal microstructures or the lamellar microstructure with wide α-platelets. These mechanical behaviors exhibited by postshock materials are closely related to the shock-induced microstructure evolution. Dislocations more tend to nucleate and interact in large-sized α phases such as equiaxed primary α and wide α-platelets. The generation of high-density micro-defects during the propagation of shock waves results in the improvement of strength but degradation of ductility of Ti64 during dynamic reloading process.

Abstract: The 3D printed cubic bulk specimens (10x10x10 mm) were fabricated by Selective Laser Melting (SLM) additive manufacturing (AM) technology from TiAl6V4 powder, using different layer thickness (from 40 to 60 μm), for investigation of the influence of layer thickness on microstructure of SLM-fabricated TiAl6V4.

Abstract: In this paper, the effect of process parameters on quality of fabricated wall, the phase composition, microhardness, and mechanical properties of the Ti-6Al-4V titanium sample, obtained by direct laser deposition, was considered. To determine the characteristics of the samples the X-ray diffraction, scanning electron microscopy, Vickers microhardness measurements, and uniaxial tensile tests were used. It is shown that the process parameters with the same speed, oscillation amplitude and peak value of heat flux have a similar wall thickness but different waviness with high mechanical properties.

Abstract: In this article has carried out X-ray phase analysis of the samples obtained using direct laser deposition. Two groups of samples were studied: the first one was obtained with oscillation of laser radiation, the second one – without. The investigations have shown that in the process of direct laser deposition, the α+β phase is formed from a Ti-6Al-4V titanium alloy with oscillation of laser radiation.

Abstract: Titanium and titanium alloys have a large array applications attributed to its low density, good corrosion resistance and high specific strength. Damage to the surface can be improved by surface modification for extended application. Direct laser metal deposition (DLMD) technique can be used to address the limitations associated with titanium alloy. This is mostly achieved by integration of reinforcement materials into the main matrix to form coating. Thereby inducing microstructural changes to the material. The morphology and also the hardness property of the various composite coatings were examined. The hardness of the composite coating was found to range between 450.64 and 638.22 HV, and the hardness obtained for 10% SiC reinforcement coating was 638.22 HV. For all the coatings, the hardness was established to be much higher than that of the substrate, which was averaged 304.21 HV. Hardness value increases with increase in SiC content. The enhanced hardness values were due to refined grains and intermetallics in the microstructure of the coatings. Moreover, the highest tensile and yield strengths was found at 10 wt.% SiC due to the uniform particle dispersion that can impede dislocation movement. The uniform distribution of SiC particles in the Al-Sn matrix had a good effect on its mechanical properties.