TC4 Titanium Alloy Research Articles

Variable cycle fretting conditions meditated wear behavior and mechanism in a self-lubricating composite coating on TC21 titanium alloy substrate

To simulate the variational working conditions of the titanium fastener in the aero-engine, variable cycle fretting wear tests were carried out for normal loading (80/40 N), frequency (100/30 Hz), displacement amplitude (80/40 µm) and operating temperature (500/350 °C) in a self-lubricating composite coating on TC21 titanium alloy substrate, and the fretting wear behavior and wear mechanism were thoroughly investigated. The results shows that the coefficient of friction (COF) and the wear volume present a significant difference under variable cycle fretting conditions. The specimen exhibits a relatively stable COF under variable operating temperature. Whereas for the specimen under variable displacement amplitude presents a lowest wear volume. The adhesive wear is mainly found in the specimens under variable normal loading and frequency. Whereas for the specimens under variable displacement amplitude and operating temperature, abrasive wear and oxidation wear is mainly dominated, respectively. The dissipated energy calculation results demonstrate that the variable displacement amplitude and operating temperature have greater impact on the fretting wear behavior. The microstructure analysis in the cross-section of specimens reveals that the sub-surface is composed of amorphous-nano crystalline layer, plastic deformation layer and the origin coating. Additionally, the wear mechanism of the specimens under variable fretting conditions were deeply revealed. This work can provide essential information on fretting behavior and mechanism under the variational working conditions.

Dynamic response of TB9/TC4 titanium laminated composite with strong bonding interface

Taking advantage of high strength of a titanium alloy and high ductility of the other one is performed to manufacture titanium laminated composite that is promisingly applied in high strain rate environments, but the challenge of fabricating high bonding interface of the two titanium alloys still needs to be overcome. In this work, the TB9/TC4 titanium laminated composite was successfully prepared by hot rolling. A strong bonding interface was constructed between the layers of TB9 and TC4 titanium alloys, achieving a high shear strength of up to 770 MPa. The dynamic compression of the TB9/TC4 titanium laminated composite under Split Hopkinson Pressure Bar (SHPB) showed that the stress-strain curve of the composite presented a unique dual-peak feature, indicative of an excellent strain hardening capability. The TB9/TC4 interface, characterized by coherent and low interface formation energy, facilitated deformation accommodation between TC4 and TB9 layers. Concurrently, the TB9/TC4 interface hindered the ASBs and triggered dislocation strengthening due to stress concentration, leading to high dynamic strength of the laminated composite.

Transfer learning-based quality monitoring of laser powder bed fusion across materials

Laser powder bed fusion (LPBF) is a promising additive manufacturing (AM) technique that has gained rapid growth. Despite the unique advantages such as producing complex-shaped metal parts, LPBF has been still slowed by the poor process repeatability and part consistency. In-situ monitoring methods combining sensing sensors and machine leaning (ML) tools have attracted much attention for defect detection and quality identification. However, the current ML algorithms usually rely on the availability of massive labeled datasets, and the trained model for monitoring a certain powder material cannot be directly applied to monitoring another material with different properties. Moreover, for a new material, it is time-consuming and expensive to collect the sufficient labeled data for building the quality monitoring model from scratch. To this end, motivated by transfer learning (TL), we propose a TL-based quality monitoring approach across two different materials in the LPBF process. Three different sensing datasets of layer-wise images of the solidified layer, photodiode signals, and acoustic emission signals are separately transferred from the 316L stainless steel to the TC4 titanium alloy. A convolutional neural network (CNN)-based quality monitoring model is first built by the sufficient source datasets from 316L stainless steel material. Then, the pre-trained CNN model is fine-tuned with a small amount of the target datasets for quality monitoring on TC4 titanium alloy material. Experimental results demonstrate the effectiveness of the proposed method for quality monitoring from one material to another with limited target datasets, with a classification accuracy above 92 % just with 5 % of target datasets on all three transferred datasets.

Effect of copper addition on passivation film of TC18 titanium alloy

TC18 and TC18–0.5Cu alloys were prepared by vacuum arc furnace melting. The properties of its passivation film in 5 % NaCl solution were investigated using constant potential polarization, electrochemical impedance spectroscopy, Mott-Schottky and XPS analysis. The corrosion resistance of TC18 passivation films was found to be superior to that of TC18–0.5Cu alloy. The passivation films formed on both alloys displayed n-type semiconductor behavior. In the TC18–0.5Cu alloy, the presence of copper as a form of copper interstitial segregation Cuix+ was observed, which was subsequently replaced by low-mobility titanium ionic vacancies in the form of a cationic sublattice CuTix′, as a small defect.

The microstructures and mechanical properties of the TC4 titanium alloy fabricated by laser composite manufacturing technology

The effective combination of traditional forging and laser three-dimensional forming technology can play a crucial role in the preparation of large metal part with fine structures, thereby accelerating the manufacturing cycle of parts and reducing costs. This study used laser composite manufacturing technology to perform complete annealing heat treatment on TC4 titanium alloy structural part produced from traditional forgings. The analysis of microscopic structure, chemical composition, and mechanical properties has verified that the overall mechanical properties consistency of the composite manufacturing part has been effectively improved. The results indicate that laser composite manufacturing part have good metallurgical bonding, and there is no component segregation phenomenon in the composite manufacturing area. After complete annealing, the α lath in the composite manufacturing part is coarsened, the strength of the laser forming area is reduced, and the consistency of mechanical properties of the forging area and the laser forming area is enhanced. The consistency of strength of the two areas is increased from 78% before heat treatment to 84%.

Effect of three-stage heat treatment on mechanical properties and micro-deformation mechanism of TC4 titanium alloy welded joint

The influence of three-stage heat treatment on the microstructure and mechanical properties of pulsed laser-arc hybrid welded TC4 titanium alloy joints was studied by experiments and molecular dynamics calculations. The results showed that after the three-stage heat treatment, a large number of fine and diffusely distributed secondary α phases were found in the welded joint, which increased the content of the phase boundary. The TEM characterization and calculation results show that the phase boundary had a strong hindering effect on the dislocation slip. As a result, under three-stage heat treatment conditions, the hardness of the welded joint was increased by 50%, and the yield strength and tensile strength of the welded joints were increased by 24.3% and 13.9%, respectively. The impact toughness of the base metal significantly improved after heat treatment, which was 31.6% higher than that before heat treatment due to the increase in the equiaxed α phase from the weld metal to the base metal. A large number of stacking faults were generated during the tensile deformation of the welded joint before heat treatment due to the low stacking fault energy of the α phase, which could effectively release the stress and hinder the dislocation slip. After heat treatment, the stacking fault of the welded joint decreased owing to the obvious increase in stacking fault energy. The micro-cracks propagated rapidly along the lamellar α phase to fracture. Therefore, the plasticity of the welded joint decreased, although the strength was improved after heat treatment.

Investigation of hot deformation behavior and microstructure evolution of TC18 alloy and establishment of constitutive equation under friction-temperature correction

The effects of deformation temperature and strain rate on the microstructure evolution of TC18 alloy are studied by hot compression experiment and EBSD test, based on the double correction of friction and temperature rise in hot compression, a more accurate constitutive equation and thermal processing diagram are established. Recrystallization grain is the main microstructure of TC18 alloy during deformation from 810 °C to 930 °C. Higher deformation temperature and lower strain rate are beneficial to the occurrence of dynamic recrystallization and grain size growth. The strain rate has no significant effect on volume fraction of large and small angle boundary. After double correction of temperature rise and friction, it is found the activation energy of TC18 titanium alloy in β region and α/β region are 485.895 kJ/mol and 355.337 kJ/mol, respectively. The ideal hot working conditions of TC18 titanium alloy are 812 °C ∼ 840 °C, 0.01 s−1 ∼ 0.018 s−1 and 878 °C ∼ 915 °C, 0.178 s−1 ∼ 1.0 s−1, respectively. The unevenness of microstructure, the large size difference among grains and the large orientation difference among grains lead to the instability of hot working process. The conclusions of this paper can provide more accurate guidance for the determination of hot working parameters and the prediction of microstructure evolution during hot working of TC18 alloy.

Dynamic response and roughness control of surface materials on TC4 titanium alloy subjected to laser shock wave planishing

Abstract In this study, ABAQUS was used to predict the dynamic response of surface materials on TC4 titanium alloy during laser shock wave planishing (LSWP). The experiments were conducted to evaluate the simulations. The results indicate that during the initial stage of LSWP, the contact status between the contact foil and the micro-protrusion changes from the one-dimensional stress state to the one-dimensional strain state. This causes the high-amplitude tensile residual stress to converge at the center of the flattened micro-protrusion surface. When treating specimens with high surface roughness, the application of a thin contact foil can significantly lower the height of micro-protrusions and lift the bottom of micro-depressions. This improves the plastic flow of micro-protrusions and prevents the convergence of tensile residual stress. Using a thick contact foil can help extend the pressure pulse duration and prevent the overall surface profile subsidence when treating specimens with lower surface roughness. The outcomes of the experiment and the simulation agree rather well. Additionally, a thick contact foil can reduce the build-up of tensile residual stress by reducing the contact pressure.

Construction of a Predictive Model for Dynamic and Static Recrystallization Kinetics of Cast TC21 Titanium Alloy

In this study, hot compression experiments were conducted on cast TC21 titanium alloy using a Gleeble-1500D thermal simulation compression tester, and the hot-compressed specimens were heat-treated. The data obtained after analyzing the thermal compression of cast TC21 titanium alloy were analyzed to construct a thermal machining diagram with a strain of 0.8 and to optimize the machining window. This study investigated the microstructure of the alloy after hot pressing experiments and heat treatment, applying the study of the microstructure evolution law of cast TC21 titanium alloy. The analysis of the tissue evolution law established the dynamic and static recrystallization volume fraction as a function of heat deformation parameters. The results show that the optimal processing window for cast TC21 titanium alloy is a deformation temperature in the range of 1373 K–1423 K and a strain rate of 0.1 s−1. The increase in deformation volume and deformation temperature both favor recrystallization and make the recrystallization volume fraction increase, but the increase in strain rate will inhibit the increase in the recrystallization degree to some extent. The dynamic and static recrystallization equations for the cast TC21 titanium alloy at different temperatures were constructed. The experimental measurements of recrystallization volume fraction are in good agreement with the predicted values.

Effect of ultrasonic rolling on the fatigue performance of laser-welded TC4 titanium alloy joints

Effect of ultrasonic rolling on the fatigue performance of laser-welded TC4 titanium alloy joints

Research on the Preparation of Zirconia Coating on Titanium Alloy Surface and Its Tribological Properties

Titanium alloys have been widely used in aerospace and other fields due to their excellent properties such as light weight and high strength. However, the extremely poor tribological properties of titanium alloys limit their applications in certain special working conditions. In order to improve the tribological properties of titanium alloys, the zirconia coatings were prepared on the surface of a TC4 titanium alloy using the discharge plasma sintering method in this article. The influence of sintering parameters on properties such as density, adhesion, hardness, and phase composition, as well as tribological properties (friction coefficient, wear rate) were investigated, and the influence mechanism of the coating structure on its mechanical and frictional properties was analyzed. The results showed that, with the increase in sintering temperature, the density, bonding strength, and hardness of the zirconia coating were significantly improved. The zirconia coating prepared at a sintering temperature of 1500 °C and a sintering time of 20 min had the lowest friction coefficient and wear rate, which are 0.33 and 6.2 × 10−8 cm3·N−1·m−1, respectively. Numerical analysis showed that the increase in temperature and the extension of time contributed to the extension of the diffusion distance between zirconia and titanium, thereby improving the interfacial adhesion. The influence mechanism of different sintering temperatures and sintering times on the wear performance of zirconia coatings was explained through Hertz contact theory.

A Laser-Induced TIG Arc Narrow-Gap Welding Technique for TC4 Titanium Alloy Thick Plates Based on the Spatial Position Control of Laser, Arc and Filler Wire

In this paper, a novel laser-induced TIG arc narrow-gap welding technology is proposed for thick plates of TC4 titanium alloy. The feasibility of achieving high-performance welding joints is investigated by adjusting the spatial deviation position of the laser, arc, and filler wire. The results exhibited remarkable capabilities. By augmenting the laser-arc malposition, a stable deflection of the arc can be achieved, resulting in enhanced heat input to the sidewall adjacent to the laser side and improved fusion capability. Moreover, an inclined weld can be obtained through increased malposition between the filler wire and arc, which helps to improve interlayer fusion and suppress porosity defects. This method, involving alternating bilateral offsets between passes, successfully achieved narrow-gap welding of 24 mm-thick TC4 titanium alloy with an average tensile strength of 880.68 MPa (equivalent to 95.05% of base material strength). Therefore, this technology exhibits promising potential as an automated welding technique for achieving high-quality narrow-gap welding in titanium alloys.

Research on surface integrity of TC4 titanium alloy by ultrasonic surface rolling peening

Research on surface integrity of TC4 titanium alloy by ultrasonic surface rolling peening

High-efficiency and low-damage modification of engineering metal materials by oxygen-mixing atmospheric pressure cold plasma jets

Engineering metal materials have been widely developed and applied in aviation, aerospace and biomedicine fields. Wettability improvement of these materials can alleviate problems caused by low adhesion and poor bioactivity, thereby facilitating their practical applications. Compared with other methods, atmospheric pressure cold plasma treatment has better versatility and can efficiently improve wettability without causing serious damages, and has therefore been widely used in polymer hydrophilization. However, when treating metal materials, the cold plasma may induce surface breakdown or have low efficiency. In this paper, we developed a new cold plasma jet by mixing oxygen into working gas to achieve high-efficiency and low-damage modification. When oxygen mixing ratio was 0.4 %, the cold plasma jet could modify TC4 titanium alloy surface to be superhydrophilic within 20 s, which was much more efficient than traditional plasma jet (120 s). We then further investigated the mechanism contributing to higher efficiency, and found that the oxygen-mixing plasma jet did not cause serious damages, while generating more polar groups by higher-concentration active particles, as confirmed by surface energy calculation and optical emission spectra. Besides titanium alloy, the oxygen-mixing plasma jet could also achieve rapid hydrophilization of various engineering metal materials, showing promising application prospects.

Anomalous enhancing effects of electric pulse treatment on strength and ductility of TC17 linear friction welding joints

Mechanical properties of TC17 titanium alloy undergo a significant reduction after linear friction welding (LFW), of which the strength and ductility are hard to be improved simultaneously by traditional aging heat treatment (AHT), seriously limiting the application of LFW in the manufacturing of TC17 titanium alloy blisks. To this end, the present work proposes to use electric pulse treatment (EPT) to enhance the strength and ductility of TC17 LFW joints simultaneously by improving its microstructure. The results show that, in comparison to the uneven distribution of α phases in the welding zone (WZ), heat-affected zone (HAZ), and base metal (BM) zone after AHT, EPT can selectively homogenize the α phase distribution of WZ and HAZ without impacting the BM. The selective effect of EPT is reflected as the synergistic influence of the local Joule heating effect and the electron wind effect, which promotes the diffusion of β phase stabilizing element Mo and leads to a competitive precipitation of β phase and α phase in the α phase transition temperature range. The ratio of α phase to β phase in the WZ and HAZ finally approaches an equilibrium point which is similar to that of BM, leading to a uniform distribution of α phase and realizing the synergy of strength-ductility of LFW joint: the maximum strength increase observed is 12.9 %, accompanied by a corresponding elongation increase of 122 % (by AHT & EPT), and the maximum plasticity improvement is 185 %, accompanied by a corresponding strength increase of 4.3 % (by EPT for 1 h). This study provides essential insights for improving the strength and ductility of LFW TC17 titanium alloy blisks and enhancing the applications of LFW in aeroengine components.

Simulation of Solidification Structure in the Vacuum Arc Remelting Process of Titanium Alloy TC4 Based on 3D CAFE Method

Vacuum arc remelting is the main production method of titanium alloy ingots at present. In order to obtain good quality ingots, it is of great significance to study the formation of the solidification structure of ingots via vacuum arc remelting. In order to select and optimize the nucleation parameters for the solidification microstructure simulation of an ingot, a 3D CAFE model for microstructure evolution during vacuum arc remelting was established, taking into account heat transfer, flow, and solute diffusion. The Gaussian distribution continuous nucleation model and extended KGT model were used to describe the grain nucleation and dendrite tip growth rates, respectively. The multi-point mass source and moving boundary method were used to simulate the ingot growth. The results show that there are three typical crystal regions in the solidification structure of vacuum arc remelting titanium alloy ingots, namely the surface fine crystal region, columnar crystal region, and central equiaxed crystal region. The proportion of the columnar crystal region in the solidification structure of an ingot increases gradually with the increase in the undercooling of the maximum bulk nucleation. With an increase in the maximum bulk nucleation density, the equiaxed grain zone gradually increases, and the grain size gradually decreases. The proportion of the columnar crystal region in the solidification structure of an ingot increases gradually with an increase in the undercooling of the maximum bulk nucleation. The maximum volume nucleation variance has no obvious effect on the change in the solidification structure. When the maximum volume nucleation undercooling is 5.5 K, the maximum volume nucleation standard deviation is 4 K, and the maximum volume nucleation density is 5 × 108. The solidification structure simulation results are in good agreement with the experimental results.

Microstructure and anti-ablation of laser cladding Ti-Zr-B-C coating on TC11 titanium alloy

To enhance the service life and application range of titanium alloys in the aerospace sector, Ti-Zr-B-C coatings with varying B4C contents (0–30 wt%) on TC11 titanium alloy was fabricated by laser cladding. The microstructure and anti-ablation were investigated in the present work. The results show that the whisker-like TiB phases and granular TiC and ZrC phases were observed in the coatings due to the in-situ reactions. With increasing the content of B4C, the number of reinforcing phases in the coating increased and distributed uniformly, resulting in the improvement of the microhardness up to 803.8HV. Furthermore, due to the formation of TiO2-ZrO2-B2O3 dense multiphase oxide layer on the surface during the ablation process, the coating with 20 wt% B4C exhibited the best anti-ablation at 1400ºC, the mass ablation rate (MAR) and linear ablation rate (LAR) were −2.62 mg/s and 3.67μm/s, respectively, which were just 62.8 % and 50.07 % in comparison with the substrate. This is mainly attributed to the formation of TiO2-ZrO2-B2O3 layer is beneficial to reduce the infiltration of O2 and the evaporation of liquid B2O3, leading to the excellent anti-ablation.

A promising approach to enhance fatigue life of TC11 titanium alloy: Low dislocation density and surface grain refinement induced by electropulsing

The fatigue life of components can be significantly enhanced by the formation of the surface hardness layer through surface strengthening technology. To avoid the geometric distortion of thin-walled components caused by strengthening, the strengthening energy is limited and the ideal strengthening effect cannot be obtained. This work aims to propose a novel approach to address this issue effectively. The surface layer with high-density dislocations was obtained by a low-energy surface strengthening method (shot peening) at first. Then the surface strengthening mechanism changes from dislocation strengthening to grain boundary strengthening after electropulsing treatment (EPT). The evolution of residual stress and microstructure was analyzed using multi-scale characterization techniques. The results demonstrate that EPT followed by surface strengthening makes a remarkable 304 % increase in fatigue life of TC11 titanium alloy. The enhancement of fatigue life can be attributed to the grain refinement accompanied by the formation of nanotwins and sub-grains in the surface-strengthened layer, as well as the reduction in dislocation density within the substrate after EPT. This study demonstrates the significant potential of EPT in further enhancing the fatigue life of surface pre-strengthened thin-walled components.

Interface evolution mechanism and mechanical properties of Ti311/TC4 laminated composites during hot-pressing diffusion bonding

The dual-hardness titanium alloy laminated composites exhibit high hardness and toughness, making it an ideal material for applications in ballistic protection, wear-resistant and other fields. However, the substantial difference in hardness poses a challenge in effectively bonding these alloys, potentially resulting in the emergence of cracks and a decrease in bonding strength. In this study, a new Ti5Si3-reinforced high-hardness Ti311 (475 HV) and TC4 (352 HV) titanium alloys were successfully combined by hot-pressing diffusion bonding. The synergy effects of hot-pressing temperature and deformation on the microstructural evolution and mechanical properties of the Ti311/TC4 interface were systematically studied. The metallurgical bonding interface was formed at 850 °C under 25 MPa of 15.9% deformation, with the maximum shear strength value of 606 MPa. Moreover, a continuous and discontinuous coupled dynamic recrystallization mechanism was revealed. Deformed α grains were transformed to fine recrystallized grains, and gradually grew with the help of continuous dynamic recrystallization to eliminate the original flat interface. In addition, with the occurrence of element diffusion, the interface between Ti311 and TC4 is ultimately successfully bonded. Notably, the Ti5Si3 phase played a double-edge sword effect on bonding the Ti311/TC4 interface, promoting the occurrence of continuous dynamic recrystallization of adjacent α phase in TC4, but having negative effects on element diffusion.

Weld formation and porosity in TC4 joint by oscillating laser beam welding with circle trajectory model

The pores problem is a challenging problem in laser beam welding titanium alloy TC4. Oscillating laser beam welding, as a new welding process, can effectively control the behavior of the molten pool, and is beneficial to the escape of pores, which holds promise for achieving high quality TC4 joint. Selecting appropriate oscillation parameters is the key to obtaining high quality TC4 joint by LBW. This project will focus on researching the effects of oscillating parameters on weld formation and porosity of TC4 joint by oscillating laser beam welding. Firstly, the oscillating laser beam welding experimental platform was set up, and experiments on oscillating LBW were designed and conducted. Subsequently, the microstructure of TC4 joint was analyzed, and the effects of oscillating frequency and oscillating amplitude on weld formation were studied, and the effects of oscillating frequency and oscillating amplitude on porosity were researched. The results indicate that oscillating laser beam welding with circle trajectory model can achieve high quality TC4 joint. The porosity of weld by oscillating LBW with oscillation amplitude as 1 mm and oscillating frequency as 80 Hz reaches 0.13% in value which is the lowest among the experiment cases under the condition as fixing the oscillation amplitude 1 mm in value and varying the oscillation frequency from 40 Hz to 240 Hz. When the oscillation amplitude exceeds the critical value 2.5 mm, the weld by oscillating LBW exhibits noticeable undercutting and asymmetry. The undercutting occurs on the advancing side in oscillating LBW with circle trajectory model. To a certain extent this study enriches the theory of oscillating LBW, and can provide fundamental data for oscillating laser beam welding on TC4.