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This study prepared PEO coatings on TC4 alloy in a sodium aluminate system and conducted fretting wear tests to investigate the effects of electrolyte concentrations on the fretting wear performance of coatings. The results indicated that the fretting wear performance and the fretting wear mechanisms of the coating changed with electrolyte concentration. Within a certain range, the fretting state of the coating and its resistance to fretting wear improved as the electrolyte concentration increased, leading to a decrease in adhesive effects. The wear mechanism transitioned from adhesive wear to abrasive wear, and then to slight scratching. However, when the electrolyte concentration reached 8 g L−1, it caused an increase in internal defects within the coating, which enhanced the fatigue wear during the fretting process. All coatings also exhibited oxidative wear during fretting. These findings provided a reference for the surface protection of TC4 alloy and the optimisation of PEO coatings. [ABSTRACT FROM AUTHOR]

Coarse β-grains and severe surface oxidation are major factors plaguing the comprehensive properties of tungsten inert gas (TIG) welded joints of titanium alloy. To improve the performance of welded joints, a novel current waveform, alternating current/direct current (AC/DC) mixed current waveform which was named Mix-TIG was proposed. In Mix-TIG, the oxide film on the weld surface is broken up by the cathodic crushing effect. Cyclic variations of the current waveform produce stronger arc stirring and more intense oscillations in the molten pool which results in grain refinement. In addition, the lower temperature gradient in the melt pool due to the smaller heat input in Mix-TIG also contributes to grain refinement. The elongation and microhardness of the Mix-TIG were increased. [ABSTRACT FROM AUTHOR]

Currently, the quartz glass–TC4 dissimilar joint has been applied in fields such as radiation environment testing, reactor engineering, and other areas. However, the high brittleness of the quartz glass and thermal mismatch during the welding process limit require further development. Thus, a femtosecond laser was employed to perform the direct joining of these materials under non-optical contact conditions, with the aid of a well-designed clamp and optimized process, and the effect of pulse energy on the microstructure and mechanical properties was analyzed. It was revealed that a lot of welding zones form at the interface through the diffusion of Si, O, and Ti and, thus, consist of a stable joint. Element distribution is related to pulse energy, which can affect the composition of secondary phases in the weld zones. The maximum shear strength of joints was 10.4 MPa with laser pulses of 0.3 mJ, while a further increase in the pulse energy led to more defects and stress unevenness. These findings provide valuable insights into enhancing the reliability of metal–glass welding joints and the promotion of femtosecond laser technology. [ABSTRACT FROM AUTHOR]

The TC4 alloy has become an ideal material for marine engineering due to its excellent corrosion resistance, high specific strength and light weight in seawater. However, components made from TC4 alloys often come into contact with parts such as propellers and turbine engine blades, leading to severe fretting wear during operation and significantly reducing their service life. In this study, the untreated TC4 alloy samples were used as the control group, and the samples after 240 min of surface mechanical attrition treatment (SMAT) were selected to investigate the fretting wear behavior under different load conditions in artificial seawater environment. The results show that the friction coefficient of TC4 alloy remains relatively unaffected by load variations, both before and after SMAT treatment. With the increase of load, the fretting regime gradually changed from gross slip to partial slip, and the wear depth, volume and wear rate increased. Under the same load, the wear volume of TC4 alloy after SMAT treatment is significantly reduced, indicating that its wear performance has been improved. [ABSTRACT FROM AUTHOR]

In this study, plasma nitriding and multi-arc ion plating techniques were employed to enhance the load-bearing capacity of the TC4 alloy. The tribological properties were characterized, and the mechanisms were discussed in detail. Subsequently, the tribological properties of the coating enhanced with MoS2 were then evaluated, and the results indicated that the plasma nitriding treatment, which exhibited optimal friction performance, resulted in the formation of a nitrided layer with a thickness of 98 μm on the surface of the TC4 alloy, thereby significantly improving its mechanical properties. Furthermore, the TiN coating samples treated with plasma nitriding demonstrated superior mechanical properties, achieving the highest hardness value (20 GPa), high load-carrying capacity (58 N) and the lowest wear rate (9.16 × 10−6 mm3·N−1·m−1). Moreover, the tribological properties of MoS2 deposited on the surface of the PN-2/TiN sample were significantly enhanced, which can be attributed to the synergistic effect of the excellent load-bearing characteristics of the plasma nitriding treatment and the wear resistance of the TiN layer. This study investigates the factors contributing to the superior tribological performance of the PN-2/TiN sample and the extended friction lifetime of the PN-2/TiN/MoS2 sample. The composite coating provides a new method to improve the anti-friction of soft metals, especially titanium alloys, and is expected to be applied in the aerospace field. [ABSTRACT FROM AUTHOR]

Context: Microstamping has been shown to enhance the surface strength of alloy materials by improving interatomic density. This paper delves into the damage mechanism of TiAl6V4(TC4), which has been processed using high-speed stamping with varying overlap ratios at the atomic level. Additionally, the general trend of stress variation between loading and unloading is discussed. The mechanical properties of the substrate and the changes in microstructure resulting from varying overlap rates in microstamping were investigated. The impact of different machining overlap ratios on the depth of the damaged layer, the number of dislocation density lines, and the density of the matrix is also explored. The results indicate that the dislocation density remains relatively unchanged due to material hardening, while the overlap ratio increases continuously. Based on this analysis, a more optimal microstamping overlay ratio parameter is proposed to effectively enhance the surface strength of the substrate and reduce processing time. Method: First, an alloy model with titanium, aluminum, and vanadium was created in ATOMSK and LAMMPS software. The model was divided into three layers: fixed, constant temperature, and Newton. To ensure the accuracy of the simulation, the system was annealed in order to minimize energy and replicate real-world conditions. Zhou's EAM alloy potential was employed to represent the interaction between the alloy atoms, while the Tersoff potential was used to represent the interatomic interaction of the diamond indenter. Additionally, the LJ potential function was selected to depict the interaction between the metal atom and the diamond indenter. The construct surface mesh method in OVITO software was then utilized to construct a surface mesh and analyze the impact of different machining overlap rates on surface topography. The common neighborhood analysis (CNA) module in OVITO was used to calculate the number of defective atoms and the depth of the damaged layer. Finally, the DXA (dislocation extraction analysis) module in OVITO was used to calculate the dislocation density length and dislocation density. [ABSTRACT FROM AUTHOR]

TC4 titanium alloy has been widely used in the automotive field due to its exceptional properties. However, inherent defects such as low hardness and poor wear resistance for TC4 alloy limited its wider application. The microarc oxidation (MAO) technique was employed in this paper to prepare MAO coatings on TC4 titanium alloy. The microstructure, phase structure, mechanical properties, and tribological performance were systematically evaluated. The results show that the coating contains a large amount of rutile TiO2 hard phase after MAO treatment, which significantly improves the mechanical properties of the substrate. The hardness of the MAO coating can reach 581 HV.05. Furthermore, the synergistic lubrication effect of onion‐like carbon (OLC) nanoparticles and organic molybdenum dithiocarbamate (MoDTC) in PAO oil was observed for MAO‐treated TC4. Particularly, when.01 wt.% OLC is used with 1 wt.% MoDTC oil, the coefficient of friction (COF) decreases to.062, and the wear rate decreases to 4.3 × 10−7 mm3/Nm. Combined Raman and X‐ray photoelectron spectroscopy (XPS) analysis indicate that OLC is deposited on coating area to form a lubricating carbon film. Additionally, OLC can promote the decomposition of MoDTC during sliding to generate a tribofilm containing MoS2. [ABSTRACT FROM AUTHOR]

The microstructure of three rolling surfaces of TC4 sheet is different, and their resistance ability to hydrogen damage lacks systematic research. Thus, the hydrogen damage behavior of TC4 rolling sheet was investigated in this paper. The hydrogen diffusion law along different rolling directions and the precipitation of hydrides on different rolling surfaces were compared. It is found that the shape and distribution of α and β phases are changed under the action of extrusion force during the rolling process, and they are arranged in striped shape on the R-N surface along the R direction, and the diffusion of hydrogen along the R direction is faster due to the existence of continuous β phases as hydrogen diffusion channels, resulting in the more serious hydrogen damage. Besides the hydrides mainly deposited at the α and β phase boundaries, the hydrides precipitated in the interior of α phases on the R-N surface are more than that on the R-T surface due to the different distribution state of β phases. [ABSTRACT FROM AUTHOR]

The TC4 alloy has become an ideal material for marine engineering due to its excellent corrosion resistance, high specific strength and light weight in seawater. However, components made from TC4 alloys often come into contact with parts such as propellers and turbine engine blades, leading to severe fretting wear during operation and significantly reducing their service life. In this study, the untreated TC4 alloy samples were used as the control group, and the samples after 240 min of surface mechanical attrition treatment (SMAT) were selected to investigate the fretting wear behavior under different load conditions in artificial seawater environment. The results show that the friction coefficient of TC4 alloy remains relatively unaffected by load variations, both before and after SMAT treatment. With the increase of load, the fretting regime gradually changed from gross slip to partial slip, and the wear depth, volume and wear rate increased. Under the same load, the wear volume of TC4 alloy after SMAT treatment is significantly reduced, indicating that its wear performance has been improved.

To improve wear resistance and corrosion behavior of TC4 alloy, plasma electrolytic oxidation (PEO) was performed in a TiC particle containing electrolyte. Results show that increasing PEO current density is conducive to improving the coating thickness, promoting incorporation of TiC particles, and enhancing wear resistance of the coating. While increasing TiC content in electrolyte reduces PEO coating thickness. Under the optimized condition, where the electrolyte has 2 g L−1 TiC and PEO current density is 5 A dm−2, the derived PEO coating exhibits both high wear resistance and corrosion resistance. Moreover, it is shown that the incorporated TiC particles are more likely to become components in the inner layer of the derived MAO coating.

Zr-Y modified silicide coating was deposited on TC4 alloy by the pack cementation process. The microstructure， friction and wear performance， and wear mechanisms of the coating were investigated. The results show that the Zr-Y modified silicide coating has a multi-layer structure， an outer layer consists of TiSi2 and a small amount of ZrSi2， a thin middle layer is TiSi， and an inner layer is a mixture of Ti5Si4 and Ti5Si3. The micro-hardness of the coating is much higher than that of the TC4 substrate and exhibits an obvious decrease tendency from the surface to the interior. The Zr-Y modified silicide coating possesses good anti-wear performance when wearing against GCr15 and Al2O3 balls at a high-temperature of 600 ℃. When wearing against GCr15， the wear rate of the coating is about 3.59×10-5 mm3/（N·m）， which is about 36.6% of that of the TC4 substrate， and the main wear mechanisms are characterized by the adhesive of GCr15 on the coating surface and oxidation wear. When wearing against the Al2O3 ball， the wear rate of the coating is about 9.75×10-5 mm3/（N·m）， which is about 18.9% of that of the TC4 substrate， and the wear mechanisms are fatigue wear， oxidation wear， and adhesion wear.

Currently, the quartz glass–TC4 dissimilar joint has been applied in fields such as radiation environment testing, reactor engineering, and other areas. However, the high brittleness of the quartz glass and thermal mismatch during the welding process limit require further development. Thus, a femtosecond laser was employed to perform the direct joining of these materials under non-optical contact conditions, with the aid of a well-designed clamp and optimized process, and the effect of pulse energy on the microstructure and mechanical properties was analyzed. It was revealed that a lot of welding zones form at the interface through the diffusion of Si, O, and Ti and, thus, consist of a stable joint. Element distribution is related to pulse energy, which can affect the composition of secondary phases in the weld zones. The maximum shear strength of joints was 10.4 MPa with laser pulses of 0.3 mJ, while a further increase in the pulse energy led to more defects and stress unevenness. These findings provide valuable insights into enhancing the reliability of metal–glass welding joints and the promotion of femtosecond laser technology.

In this study, plasma nitriding and multi-arc ion plating techniques were employed to enhance the load-bearing capacity of the TC4 alloy. The tribological properties were characterized, and the mechanisms were discussed in detail. Subsequently, the tribological properties of the coating enhanced with MoS2 were then evaluated, and the results indicated that the plasma nitriding treatment, which exhibited optimal friction performance, resulted in the formation of a nitrided layer with a thickness of 98 μm on the surface of the TC4 alloy, thereby significantly improving its mechanical properties. Furthermore, the TiN coating samples treated with plasma nitriding demonstrated superior mechanical properties, achieving the highest hardness value (20 GPa), high load-carrying capacity (58 N) and the lowest wear rate (9.16 × 10−6 mm3·N−1·m−1). Moreover, the tribological properties of MoS2 deposited on the surface of the PN-2/TiN sample were significantly enhanced, which can be attributed to the synergistic effect of the excellent load-bearing characteristics of the plasma nitriding treatment and the wear resistance of the TiN layer. This study investigates the factors contributing to the superior tribological performance of the PN-2/TiN sample and the extended friction lifetime of the PN-2/TiN/MoS2 sample. The composite coating provides a new method to improve the anti-friction of soft metals, especially titanium alloys, and is expected to be applied in the aerospace field.

To enhance the tribological properties of TC4 alloy, the plasma electrolytic oxidation (PEO) method was utilized to prepare the coating incorporated various contents of Al 2 O 3 nanoparticles (0, 3, 6, 9, 12 and 15 g/L) on TC4 alloy. The phase composition, chemical compositions, elemental distribution and microstructure of the coatings were investigated by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray computer tomography (XCT). The results revealed that the introduction of Al 2 O 3 nanoparticles into the electrolyte promoted the formation of Al 2 TiO 5 phase in the PEO coatings, and most of the nanoparticles were embedded into the coatings which reduced porosity of the coatings, but increased surface roughness. Also, the increase in the addition of Al 2 O 3 nanoparticles enhanced the microhardness of the PEO coatings due to the formation of Al 2 TiO 5. The tribological behavior of the PEO coatings was improved significantly owing to the high microhardness and porous structure of the coatings. The primary wear mechanism of the coating with 12 g/L Al 2 O 3 nanoparticles was abrasive wear as this coating formed a lubrication zone during the wear process. Besides, the friction coefficient and wear loss mass of the PEO coating prepared with 12 g/L Al 2 O 3 nanoparticles additive exhibited the excellent wear resistance compared to its counterparts. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Iron Steel Vanadium Titanium is the property of Iron Steel Vanadium Titanium Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The TC4 (Ti-6Al-4V) alloy has problems such as low material hardness, poor wear resistance, and abnormal sensitivity to adhesive wear and fretting wear. In this study, we used graphene-reinforced Ti/BN composite coatings prepared on the surface of the TC4 alloy by argon arc cladding technology. We explored the optimal content of graphene to improve its hardness and wear resistance. The physical phases and microstructures of the coatings were analyzed using an X-ray diffractometer, metallurgical microscope, and scanning electron microscope. Microhardness and wear properties of the cladding coating were measured by a Vickers hardness tester and a universal friction and wear tester. The incorporation of graphene resulted in a transformation of the reinforcing phase in the coating from TiN to Ti(N, C). The C element in the molten pool was substituted with the N element in an unending solid solution, resulting in the formation of Ti(N, C) through intermittent nucleation. As the amount of graphene in the molten pool increases, the concentration of carbon (C) also increases. This leads to the continuous growth of Ti(N, C) particles, resulting in a coarser coating structure and a decrease in coating performance. When the graphene content is 5 wt.%, the microstructure refinement of the coating is the most obvious, the microhardness is 900 HV0.2, which is 3 times higher than that of the matrix, and the wear rate is 4.9 × 10−5 mm3/(N·m), which is 4.9 times higher than that of the matrix. The wear mechanism of the coating is primarily abrasive wear with some slight adhesive wear. [ABSTRACT FROM AUTHOR]

In this work study, a comparative analysis was undertaken to investigate investigation into the cavitation erosion (CE) and corrosion behavior of laser powder bed fusion (LPBF) TC4 and as-cast TC4 in 0.6 mol/L NaCl solution. Relevant results indicated that LPBF TC4 revealed a rectangular checkerboard-like pattern with a more refined grain size compared to as-cast TC4. Meanwhile, LPBF TC4 surpassed its as-cast counterpart in CE resistance, demonstrating approximately 2.25 times lower cumulative mass loss after 8 h CE. The corrosion potential under alternating CE and quiescence conditions demonstrated that both LPBF TC4 and as-cast TC4 underwent a rapid potential decrease at the initial stages of CE, while a consistent negative shift in corrosion potential was observed with the continuously increasing CE time, indicative of a gradual decline in repassivation ability. The initial surge in corrosion potential during the early CE stages was primarily attributed to accelerated oxygen transfer. As CE progressed, the significant reduction in corrosion potential for both LPBF TC4 and as-cast TC4 was attributed to the breakdown of the passive film. The refined and uniform microstructure in LPBF TC4 effectively suppresses both crack formation and propagation, underscoring the potential of LPBF technology in enhancing the CE resistance of titanium alloys. This work can provide important insights into developing high-quality, reliable, and sustainable CE-resistant materials via LPBF technology.

Multi-wire arc additive manufacturing (MWAAM) enabled customized production with high deposition efficiency and low cost as compared to the common wire arc additive manufacturing (WAAM) technology. In this paper, two titanium alloy components were prepared using the MWAAM technique, and the microstructures, mechanical properties, and wear behaviors of Ti–6Al–4V (TC4) alloy and Ti-6.5A1-3.5Mo-1.5Zr-0.3Si (TC11) alloy were investigated. The results showed that the microstructure distribution of TC11 alloy prepared by MWAAM was more intensive and the length and width of the lamellar α-Ti phase were significantly reduced compared with that of TC4 alloy. The polar densities corresponding to the texture in the two selected regions of the TC4 alloy and the TC11 alloy were 17.30 and 17.69, respectively. The proportion of the HAGBs of the TC4 sample and the TC11 sample were 99.07 % and 99.43 %, respectively. The average microhardness on the X–Y plane of TC4 and TC11 alloys were 316.17 HV and 366.14 HV, respectively, while the average microhardness on the Y-Z plane were 318.18 HV and 358.10 HV, respectively. The average compression yield strengths of TC4 and TC11 alloys were 836.61 MPa and 1088.33 MPa, respectively. The COFs of MWAAM TC4 and TC11 samples were stable at 0.479 and 0.455 under 20 N, respectively. The COFs of MWAAM TC4 and TC11 samples were stable at 0.472 and 0.432 under 60 N, respectively. The average yield strength, average ultimate strength, proportion of HAGBs, and microhardness of TC11 alloy were all higher than that of TC4 alloy. These results indicated that TC11 alloy had advantages over TC4 alloy in terms of mechanical properties and microstructure, with higher strength and deformation resistance. The properties of titanium alloy samples prepared by MWAAM were not lower than those of titanium alloy samples prepared by single wire WAAM, while MWAAM significantly better than single wire WAAM in deposition efficiency. The results obtained in this paper can help to prepare titanium alloy components with excellent mechanical properties more efficiently in MWAAM process.

An experimental study on high cycle fatigue behavior of selective laser melting (SLM) TC4 alloy was carried out. The fatigue properties of the alloy under two sampling directions (horizontal and vertical) and two temperatures (room temperature and 400 ℃) were compared and analyzed. Also the feasibility of improving the fatigue properties of the alloy by hot isostatic pressing (HIP) was explored. The results show that the fatigue properties of the alloy after annealing are significantly anisotropic, and the fatigue properties of the vertical samples are higher than that of the horizontal ones. Compared with room temperature, the fatigue life of the alloy at 400 ℃ is reduced, but the anisotropy still exists. After hot isostatic pressing, the fatigue life of the alloy presents a certain degree of improvement, and the anisotropy of fatigue properties decreases. The fracture analysis shows that the cracks of SLM TC4 alloy mainly originate from surface and subsurface defects which are mainly pores. The statistical analysis shows that the source defect size of vertical samples is lower than that of horizontal samples, which is the main reason for the decrease of fatigue properties of horizontal samples. After hot isostatic pressing, cracks in both horizontal and vertical samples of the alloy are generated at the surface slip, and the porosity of the alloy is significantly reduced without obvious defects, and the decrease in the number of defects is the main reason for the improvement of fatigue properties of the alloy.

To study the feasibility of magnesium alloys used in aerospace vehicles and its corrosion resistance, the polarization data of HTM1 (Aerospace No.1 magnesium alloy) and TC4 (titanium alloy) were firstly measured through electrochemical tests, as well as the impedance data of HTM1 specialized electrophoretic paint. Subsequently, the simulation technology with polarization data, impedance data, aging data and service environment as boundary conditions was utilized to simulate and analyze the corrosion status of different typical ultra strong and heat-resistant magnesium alloy structural components in different service environments (service environment 1 with a salt mist concentration of 0.2 mg/L, and service environment 2 with a salt mist concentration of 2 mg/L) after 5.0, 10.0 and 17.5 a of service, respectively. Results showed that during the service process in service environment 1 and service environment 2, with the extension of service life, the protective performance of the electrophoretic paint decreased, leading to a gradual enhancement of the protective effect of HTM1 on TC4. However, due to the influence of the surface protective layer of HTM1, the protective effect was limited, leading to a certain degree of corrosion of TC4. Meanwhile, the contact area of the titanium magnesium couple in the two structural components was different, resulting in different degrees of protection for TC4. The larger the contact area between the two, the higher the degree of protection for TC4.

In this study, Keyhole tungsten inert gas (TIG) process, a new variation of traditional TIG process, was performed to weld TC4 titanium alloy with a thickness of 6 mm. The effect of heat input on microstructure and their correlation with mechanical properties and corrosion behavior was studied. The results showed that the microstructure of fusion zone and heat-affected zone changed obviously due to the change of heat input. The microstructure in the joints was transformed from equiaxed primary α and α+β lamellae to complete primary β grains, and then α′ phases were precipitated in the primary β grain. With the increase of heat input, the content and length of the acicular α′ phase grains were increased, resulting in a decrease in the number of high angel grain boundaries (HAGBs). Due to the phase strengthening effect of α′ phases, the microhardness of the joints increased, and the tensile strength increased, reaching a maximum value of 1030.1 MPa when the heat input was 1118 J/mm. The impact toughness of the joints increased firstly and then decreased. The corrosion behavior of the joints was worse than that of the base metal (BM). The best corrosion resistance was obtained when the heat input was 1046 J/mm. It concluded that the excellent comprehensive properties can be obtained when the heat input was in the range of 1046–1118 J/mm.

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Ti-6Al-4V (TC4) alloy wheel hub has exhibited some defects that affect the properties during the vertical centrifugal casting process. Therefore, the analysis of the solidification process would contribute to solving the above-mentioned problems. In this study, an orthogonal experimental design was employed to optimize the process parameters (rotational speed, mold preheating temperature, and pouring temperature) of the vertical centrifugal casting method. The effects of process parameters on the velocity field, temperature field, and total shrinkage porosity during the solidification process were explored, and the microstructure and mechanical properties of the wheel hub prepared by the vertical centrifugal casting method were also investigated. The results showed that the rotational speed mainly induced the change of the velocity field. The pouring temperature and mold preheating temperature affected the temperature field and solidification time. Based on the analysis of the orthogonal experiment, the optimal parameters were confirmed as a rotational speed of 225 rpm, mold preheating temperature of 400 °C, and pouring temperature of 1750 °C, respectively. The simulation results of total shrinkage porosity were in agreement with the experiment results. The wheel hub was composed of nonuniform α and β phases. The lath α phase precipitated from larger β grains with different orientations. Compared with the other samples at different locations, the α phase in the PM sample (middle of the TC4 wheel hub) displayed high peak intensity and uniformly distributed β phase along the radial direction of the wheel hub. Moreover, the PM sample revealed a higher tensile strength of 820 MPa and similar Vickers hardness of 318 HV compared with the other samples at different locations, which were higher than those of rolling and extrusion molding. This experiment design would provide a good reference for the vertical centrifugal casting of the TC4 alloy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to improve the high temperature oxidation resistance of TC4 alloy，an anti-oxidation ceramic coating was prepared on the surface of titanium alloy by micro-arc oxidation in the NaAlO2+ Na3PO4 electrolyte system.The phase composition and microstructure of the coating were characterized by XRD，SEM and EDS，respectively.The hardness and elastic modulus of the coating were tested by nano indenter.In addition，the high temperature oxidation resistance and thermal shock resistance of the micro-arc oxidation coating were studied.Results showed that the surface of the micro-arc oxidation coating was porous.The coating was mainly composed of Al2TiO5 and rutile TiO2 phase.The nano hardness of microarc oxidation coating was (7.8 ± 0.6) GPa，significantly higher than that of TC4 alloy [(4.0 ± 0.2) GPa].After cyclic oxidation at 700 ℃for 80 h，the weight gain per unit area of micro-arc oxidation coating was only 0.73 mg/cm2，which was far less than the weight gains of TC4 alloy (20 mg/cm2)，showing good high temperature oxidation resistance.After 25 thermal shocks at 700 ℃，the coating had no scaling，indicating excellent thermal shock resistance.Hence，it could be seen that micro-arc oxidation coating could effectively prevent the diffusion of oxygen，significantly reducing the oxidation rate of titanium alloy and improving the high temperature oxidation resistance of titanium alloy.

Laser cladding is a new technology to improve the wear resistance or corrosion resistance properties of metal parts. A finite element model of laser cladding coating was established by numerical simulation technology. The temperature field distribution was studied and analyzed during the laser cladding process at three different scanning speeds and three different laser powers. A Ni-based coating was also fabricated on the substrate by a CO2 laser. The optimum parameters of the laser cladding were selected and compared with the melt pool depth and width of the Ni-based coating. Then, the cooling rate, temperature gradient, temperature and stress fields were calculated and analyzed. The growth mechanism of the crystal structure was analyzed by scanning electron microscope (SEM). The wear resistance of the Ni-based coating was measured by a friction and wear testing machine. The results showed that the optimal parameters were laser power 1600 W and scanning speed 3 mm/s. The temperature trends at different locations were similar. The calculated maximum residual stress was 0.157 GPa. The stress concentration appeared near the surface and both sides of the cladding layer. From the coating's microstructure, it could be seen that it contained a large number of columnar dendrites, and the crystal size gradually decreased with the increase of cooling rate. The wear rates of the Ti-6Al-4V (TC4) substrate and the Ni-based coating were 6.98 mm3/(N·m) and 3.45 mm3/(N·m), respectively. The Ni-based layer had a low wear rate and good wear resistance, which is helpful to obtain good friction and wear resistance of TC4 substrates. [ABSTRACT FROM AUTHOR]

This study assessed the efficacy of models in predicting uniaxial tensile and fracture properties of Ti‐6Al‐4V (TC4) alloys via spherical indentation tests (SITs). Four models, including one empirical, one numerical, and two analytical, were selected as representatives to evaluate uniaxial tensile properties. A series of experiments were conducted on TC4 alloys obtained from three manufacturing processes: selective laser melting (SLM), forging, and welding. The empirical model underestimated the material's strength, while the other models were mostly conservative, with errors within 10%, acceptable for engineering applications. However, although the incremental model is able to provide a desirable result, it may be inaccurate for calculating the yield strength. Thus, the source of errors in each model was thoroughly investigated through theoretical analysis and finite element calculations. Additionally, based on the results of optimal strength assessment, this study validated the effectiveness of the critical stress model to evaluate the fracture toughness of TC4 alloys. Highlights: This study evaluated the mechanical properties of TC4 alloys with different indentation models.This study used the indentation response analysis of TC4 alloys from the SLM, forging, and welding.Sources of errors in each representative model were discussed in detail.Selection of the optimal stain threshold in the incremental model was examined. [ABSTRACT FROM AUTHOR]

The three-dimensional small crack growth behavior of selective laser melting (SLM) TC4 alloy was investigated by in-situ observation fatigue test method, and the long crack growth curve was measured by load reduction method under the same experimental conditions. The results show that at the early stage of small crack growth, the fatigue crack growth(FCG) rate fluctuates obviously under the influence of microstructure, and the FCG path is zigzag. With the increase of crack length, the influence of microstructure decreases, and the FCG path is straight, and the FCG rate increases steadily with the crack length. Internal defects can still reduce alloy fatigue life. Considering the small and long crack growth data, it is demonstrated that the small crack can still propagate under threshold value of long crack, and under the same stress intensity factor amplitude ΔK, small crack growth rate is higher than that of long crack. There is a typical "small crack effect", thus the small crack behavior should be considered when fatigue life prediction is carried out.

In order to explore the differences of microstructure，composition and performances of different fatty acid salt superhydrophobic coatings，three kinds of fatty acid salt superhydrophobic coatings were prepared by electrodeposition on rough surface of TC4 alloy.The microstructure，chemical composition，phase and wettability of such superhydrophobic coatings were characterized and analyzed by scanning electron microscopy，X-ray diffraction，X-ray photoelectron spectroscopy，Fourier transform infrared spectroscopy and contact angle tester.The wear resistance，heat resistance and corrosion resistance of the superhydrophobic coatings were investigated by linear friction test，long time heating experiment and electrochemical experiment respectively.Results showed that fatty acid salt coatings obtained by anodic and cathodic deposition both had non-adhesion superhydrophobicity.The surface color and state of the three fatty acid salt coatings were different，but the micromorphology was all ＂cauliflower＂ cluster，and there was an obvious micro nano hierarchical structure.The wear resistance and heat resistance of the three superhydrophobic coatings were different due to different fatty acid salts.Corrosion resistance of three superhydrophobic coatings was better than that of the substrate.CSHS-Cu had the best corrosion resistance.The Jcorr of CSHS-Cu was 1/5 of that of the bare substrate，and its Rct was 25 times that of the bare substrate.

In the current aviation industry, laser melting is an ideal technique for repairing and surface treatment of TC4 alloy parts, which has advantages over traditional metal repair techniques in terms of process. In this work, laser melting repair processes were performed on the surface of alloy specimens by different laser scanning speeds at a power of 2 kW, and the changes in metallographic organization, electrochemical corrosion properties and mechanical properties of the repaired surfaces were detected and analyzed. The results show that the significant microstructural changes are occurred during the laser repair process. The best corrosion resistance of the repaired surface is achieved at a laser scanning speed of 150 mm/min. The best microhardness and wear resistance of the repaired surface are achieved at 200 mm/min.

In this paper, TC4 alloy/304 stainless steel explosive welding composite plate is employed as the interlayer to achieve the connection of TC4 alloy and 304 stainless steel by laser doublepass welding. During the welding process, the unmelted TC4 alloy and 304 stainless steel are retained on the interlayer as the diffusion barrier to prevent the metallurgical reaction of Ti and Fe elements. Therefore, it can not only improve the interfacial organisation, but also enhance the mechanical properties of the joint. There are no Ti–Fe brittle intermetallic compounds at the joint through the XRD. The tensile failure occurs on the unmelted TC4 alloy side of the interlayer, and the maximum tensile strength of the joints can reach 840 MPa. [ABSTRACT FROM AUTHOR]

TC4 alloy is widely used in dental implantation due to its excellent biocompatibility and low density. However, it is necessary to further improve the corrosion resistance and surface hardness of the titanium alloy to prevent surface damage that could result in the release of metal ions into the oral cavity, potentially affecting oral health. In this study, Ti-N-O layers were fabricated on the surface of TC4 alloy using a two-step hollow cathode plasma source oxynitriding technique. This resulted in the formation of TiN, Ti2N, TiO2, and nitrogen-stabilized α(N)-Ti phases on the TC4 alloy, forming a Ti-N-O modified layer. The microhardness of the samples treated with plasma oxynitriding (PNO) was found to be 300–400% higher than that of untreated (UN) samples. The experimental conditions were set at 520 °C, and the corrosion current density of the PNO sample was measured to be 7.65 × 10−8 A/cm2, which is two orders of magnitude lower than that of the UN sample. This indicates that the PNO-treated TC4 alloy exhibited significantly improved corrosion resistance in the artificial saliva solutions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, a robust brazed joint of carbon fibre-reinforced carbon-based (C/C) composite and TC4 alloy was produced by utilising a slice of C/C as an interlayer. The C/C slice interlayer caused microstructural and mechanical property enhancement. During brazing, massive in situ formed carbon fibres broke away from the C/C slice bundles and were distributed in a three-dimensional interlocked network. These unique fibres consumed excessive Ti to inhibit the formation of excess brittle Ti–Cu compounds in the brazing seam. This reduced the coefficient of thermal expansion effectively, consequently relieving the high residual stress in the joint interface. The average shear strength of the joint brazed with the C/C slice interlayer reached 1.65 times higher than the directly brazed one. [ABSTRACT FROM AUTHOR]

The TC4 (Ti-6Al-4V) alloy has problems such as low material hardness, poor wear resistance, and abnormal sensitivity to adhesive wear and fretting wear. In this study, we used graphene-reinforced Ti/BN composite coatings prepared on the surface of the TC4 alloy by argon arc cladding technology. We explored the optimal content of graphene to improve its hardness and wear resistance. The physical phases and microstructures of the coatings were analyzed using an X-ray diffractometer, metallurgical microscope, and scanning electron microscope. Microhardness and wear properties of the cladding coating were measured by a Vickers hardness tester and a universal friction and wear tester. The incorporation of graphene resulted in a transformation of the reinforcing phase in the coating from TiN to Ti(N, C). The C element in the molten pool was substituted with the N element in an unending solid solution, resulting in the formation of Ti(N, C) through intermittent nucleation. As the amount of graphene in the molten pool increases, the concentration of carbon (C) also increases. This leads to the continuous growth of Ti(N, C) particles, resulting in a coarser coating structure and a decrease in coating performance. When the graphene content is 5 wt.%, the microstructure refinement of the coating is the most obvious, the microhardness is 900 HV0.2, which is 3 times higher than that of the matrix, and the wear rate is 4.9 × 10−5 mm3/(N·m), which is 4.9 times higher than that of the matrix. The wear mechanism of the coating is primarily abrasive wear with some slight adhesive wear.

The corrosion mechanism and microstructure evolution of TC4 alloy and TiC/TC4 alloy nanocomposite manufactured by laser powder bed fusion (LPBF) were evaluated comparatively using electrochemical measurements combined with microstructure characterisations. The compelling microstructural results showed that refined grains, fewer defects and stronger texture strength were the dominating internal factor for enhancing the corrosion resistance of TiC/TC4 alloy nanocomposites. Further, a uniform distribution of in situ formed nanoscale TiC reinforcements significantly promoted the formation of [TiCl 6 ]2− complexes, yielding the passivation formed again. These findings revealed that the elevated corrosion performance of LPBF-built TiC/TC4 alloy nanocomposites is due to the nanoscale TiC and strengthened microstructure inhibiting the occurrence of pitting corrosion in the alloy system during the corrosion process. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced thermosetting composites (CFRTS) and TC4 alloy are important structural materials for lightweight manufacturing. The hybrid structure of these two materials has been widely used in the aerospace field. However, the CFRTS-TC4 alloy joint formed by the traditional connection method has many challenges, such as poor environmental adaptability and stress concentration. Laser micro-texturing of metal surface-assisted laser connection of CFRTS and TC4 alloy has great potential in improving joint strength. In order to study the effect of laser micro-texturing on the laser bonding of CFRTS and TC4 alloy, the simulation and experimental research of laser welding of TC4 alloy and CFRTS based on laser micro-textures with different scanning spacings were carried out, and the interface hybrid pretreatment method of laser cleaning and laser plastic-covered treatment was introduced to assist the high-quality laser bonding of heterogeneous joints. The results showed that the established finite element model of CFRTS-TC4 alloy laser welding can predict the temperature field distribution of the joint during the welding process and reflect the forming mechanism of the joint. The laser micro-textures with different scanning spacings will lead to a difference in the temperature field distribution on the polyamide (PA6) interface, which leads to a change in heat input on the CFRTS surface. When the laser scanning spacing is 0.3 mm, the joint strength can reach 14.3 MPa. The failure mechanism of the joint mainly includes the cohesive failure of the internal tear of the carbon fiber and the interfacial failure of the interface between the PA6 resin and the TC4 alloy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)