TC4 Titanium Alloy Research Articles

Evolution of bonding mechanism and fracture mechanism of Ti alloy-steel joint by dual-beam laser welding using Mg-RE (RE=Gd, Y) filler

In this paper, a novel coaxial continuous-pulsed dual-beam laser was proposed to join TC4 titanium alloy with QP980 high-strength steel, and magnesium alloy containing rare-earth elements (Mg-RE) was creatively as filler. The weld appearance, microstructure and mechanical properties of joints obtained by single-beam and dual-beam laser welding were compared and analyzed. And the evolution of bonding mechanism and the fracture mechanism with laser beam energy density was analyzed. The results showed that the appearance and mechanical strength of the joint obtained by dual-beam laser were better than that by single-beam laser. And the maximum tensile shear load of TC4/QP980 lap joint welded by dual-beam laser reached 303 N/mm, which was 124 % of that of single-beam laser welding. The bonding of Mg-RE with QP980 affected by temperature of laser welding and mainly depended on Gd and Y. They just diffused to QP980 under low power and reacted with Fe under high power. And the inter-diffusion of Zr of Mg-RE with Ti of TC4 produced to the bonding of Mg-RE with TC4. The roles of continuous laser and pulsed laser in dual-beam laser welding were revealed in this paper and it showed a great application potential of coaxial dual-beam laser welding technology in dissimilar metal joining.

Effects of Stress Amplitude and Cold Expansion Strengthening on the Fatigue Property of TC4 Titanium Alloy

Effects of Stress Amplitude and Cold Expansion Strengthening on the Fatigue Property of TC4 Titanium Alloy

Investigation on keyhole stability and surface quality in laser welding of TC4 titanium alloy with adjustable ring-mode (ARM) laser

Investigation on keyhole stability and surface quality in laser welding of TC4 titanium alloy with adjustable ring-mode (ARM) laser

Statistical analysis of plasma thermodynamic behavior based on laser deep penetration welding of TC4 titanium alloy

The laser-induced plasma is an important characteristic that affects the welding process and weld quality. The plasma plume erupting velocity and temperature are the two critical parameters of plasma thermodynamic behavior. In this paper, a kind of passive dual-probe device was proposed to measure the erupting velocity of the plasma plume, and the feasibility of the method was demonstrated. The temperature distribution of the plasma plume was also investigated. The experimental results showed that for the reason of the state of the keyhole was different, the MPV at the beginning of the laser pulse period increased from 14 m/s to 26 m/s with the peak power increased from 1980 W to 2520 and from 4 m/s to 25 m/s with the peak power increased from 1200 W to 1500 in the pulse laser welding process, while the MPV decreased from 20 m/s to 11 m/s with the laser power increase from 1200 W to 1500 W in the continuous laser welding process. The MPT decreased with the increase of height in pulse laser welding process; but in the continuous laser welding process, the plasma plume was heated by absorbing the laser energy and a hot core occurred in the plasma plume, the MPT first increased and then decreased with the increase of probe height.

Retracted: Surface Feature Prediction Modeling and Parameter Optimization for Turning TC17 Titanium Alloy

Retracted: Surface Feature Prediction Modeling and Parameter Optimization for Turning TC17 Titanium Alloy

Mechanical Properties and Constitutive Model of TC4 Titanium Alloy at Cryogenic

Mechanical Properties and Constitutive Model of TC4 Titanium Alloy at Cryogenic

Studies on the life, damage evolution, and crack propagation behaviors of TC18 titanium alloy under repeated impact loading

TC18 titanium alloy has been widely used as the key structure which is often subjected to repeated impacts in service in aerospace engineering. In this study, the repeated impact responses of TC18 were investigated by conducting various repeated drop hammer impact tests. Abundant microscopic characterization technologies were used to reveal the correlation between damage evolution and the impact response. The results show that the average impact fatigue life (Nf¯) of the notched three-point-bend specimen decreases exponentially with the impact energy. Microscopic observation shows that cracks nucleate at the initial 40%∼50% of Nf¯, then propagate steadily during the next 50% to 90% of Nf¯. During the last 10% of Nf¯, the cracks propagate rapidly, resulting in the failure. During crack propagation, the repeated impacts induce complex stress states in the vicinity of cracks, leading to grain refinement, phase transition, and strengthened texture. The phase transition and strengthened texture mechanisms are mainly due to the generation of the platelet-like α subgrains inside the refined grains. The results in this paper are crucial for understanding the microscopic damage and failure mechanism of TC18 under repeated impacts, which helps to establish the damage accumulation-based life prediction model in the future.

Flow Characteristics Analysis of TC18 Titanium Alloy during Hot Deformation Based on Phase Transformation

Flow Characteristics Analysis of TC18 Titanium Alloy during Hot Deformation Based on Phase Transformation

Research on Surface Integrity and Fatigue Properties in the Turning of TC17 Titanium Alloy Based on the Response Surface Method.

Titanium alloy parts are more and more widely used in the field of aerospace. In order to improve the service life of titanium alloy parts, the response surface method was used to study surface residual stress and roughness under different turning parameters. In addition, a mathematical model was established through multiple linear regression to determine the relationship between surface integrity parameters and fatigue life. The test results indicate that the turning parameters have an effect on surface residual stress in the order of feed rate > depth of cut > cutting speed and on surface roughness in the order of feed rate > cutting speed > depth of cut. The analysis results of surface integrity show that the residual compressive stress on the surface has the greatest impact on fatigue life, followed by surface roughness. The fatigue life increases with the increase in residual compressive stress and decreases linearly with the increase in surface roughness. The feed rate has a significant impact on residual stress and surface roughness. Therefore, under the experimental conditions of this paper, the appropriate feed rate can be selected to ensure that the Ra < 2 μm and a large residual compressive stress is obtained.

Improving material removal rate and surface roughness in macro electrolyte jet machining of TC4 titanium alloy using tools with a converging-diverging Laval-type electrolyte channel

Improving material removal rate and surface roughness in macro electrolyte jet machining of TC4 titanium alloy using tools with a converging-diverging Laval-type electrolyte channel

Microstructure and mechanical properties of laser welded Ti-6Al-4V (TC4) titanium alloy joints

Laser beam welding (LBW) was applied to join 3 mm thick TC4 titanium alloy plates in this study. Three-factor and three-level orthogonal experiments were designed to choose the best welding parameters through the analysis of range and variance. The microstructures of the welded joints were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The mechanical properties of the welded joints were analyzed by tensile tests. The experimental results indicated that the defocused position had the largest effect, followed by the laser power and welding speed. The optimal welding parameters were laser power 2.3 kW, welding speed 0.04 m/s and defocused position 0 mm. The heat-affected zone (HAZ) consisted of α′ martensite, primary α phase (αp) and primary β phase (βp). In the fusion zone (FZ), the acicular α′ martensite was distributed in the β columnar grains. The tensile strength of the laser welded joint under the optimal welding parameters was 985 MPa, which is less than that of the base metal (BM). The peak value of the grain misorientation angle in the HAZ was related to the amount of martensite. The laser welded joints with finer martensite and equiaxed α + β would have better mechanical properties. The grains in the HAZ had a preferred orientation in the {001} direction.

Cyclic softening behavior of TC17 titanium alloy fabricated by laser directly energy deposition

In aero-engines, cyclic softening can cause premature fracture of components, which is regarded as a challenge for the security of titanium alloy parts in service. In this work, the cyclic deformation behavior of LDEDed and β-forging TC17 titanium alloys with different morphology of α phase was explored, cyclic softening mechanism was investigated by using transmission electron microscopy (TEM) observation of dislocation morphology. The experimental results demonstrate that cyclic softening occurs when the total strain range increases to 2.0 %. The LDEDed specimen has a smaller stress amplitude and a larger plastic strain during cyclic softening than wrought specimen. In the softened deformation microstructure of LDEDed specimen, the size of αp decreases with the increase of strain, but the size and shape of αp and αs in wrought specimen do not change much. The main dislocation forms that dominate the cyclic softening in the α phase and the β matrix are slip bands and dislocation tangles, respectively, and the slip band in the α phase cannot pass through the secondary phase in the β matrix for slip transfer. Under the same strain, the lower dislocation density in the LDEDed microstructure is due to the larger directional back stress produced by the forward loading, which causes the dislocation rearrangement and annihilation under the reverse loading.

Prediction of Surface Residual Stresses after Laser Shock Processing on TC4 Titanium Alloy Using Different Neural Network Agent Models

Nowadays, it has become a trend to use finite element simulation instead of experimental processes, and this is widely used in the fields of structural mechanics, fluid mechanics, fracture mechanics, and so on. By replacing the experimental process with finite element simulation, we can reduce time and costs; however, when using finite element simulation, we need to define a series of settings, such as modeling, material assignment, environment settings, and many other operations. For laser shock processing intensification, the simulation experiment process is cumbersome and time-consuming. It involves performing neural network agent modeling, replacing finite element simulation with the learning and prediction capabilities of neural networks, learning by using some of the simulation results as a training sets for the neural network, and then learning by using the remaining simulation results as testing sets to test the predictive ability of the neural network agent model. TC4 titanium alloy was selected as the experimental material. Three kinds of neural network agent models, a genetic algorithm-optimized BP network, a strong classifier design based on BP_Adaboost, and an extreme learning machine, instead of finite element simulation experiments, were used to predict the residual stresses generated on the surfaces of the material under different laser shock parameters. Comparing the prediction performances of different neural network agent models, the genetic algorithm-optimized BP network shows the best prediction performance, and its prediction value matches well with the experimental value. The R2, RMSE, and MAE of the testing sets of the BP network optimized using the genetic algorithm were 0.9985, 44.4518, and 30.6285, respectively. The BP network agent model optimized using the genetic algorithm for laser shock parameters other than the 208 sets of data also had good prediction performance, and the predicted values were similar to the actual experimental results. The prediction results show that the BP network optimized using the genetic algorithm can predict the residual stresses on the surface of TC4 titanium alloy material under strengthening via laser shock processing; the genetic algorithm-optimized BP neural network agent model is more convenient and quicker compared to the finite element simulation, and the predicted value is also similar to the actual value. It can thus be used to replace finite element simulation by establishing a more convenient and quicker neural network agent model.

In-situ growth and mechanism of MgAl-NO3-LDHs film on Ti6Al4V via one-step hydrothermal treatment with a high concentration of alkaline growth solution

The stable TiO2 passive film on titanium alloys has made it very difficult the in-situ growth of layered double hydroxides (LDHs) on their surface. In this paper, the in-situ growth of MgAl-NO3-LDHs on TC4 titanium alloy (Ti6Al4V) was successfully realized by one-step hydrothermal treatment with a high concentration of alkaline growth solution. The in-situ growth process of MgAl-NO3-LDHs on Ti6Al4V under different concentrations of growth solution was investigated by characterizing the morphology, structure and composition of the LDHs at different growth time. It was found that the key to the in-situ growth of MgAl-NO3-LDHs on Ti6Al4V was the conversion of the surface TiO2 and Al2O3 passive film to TiOH62− and AlOH4− which acted as active sites for the immobilization of LDHs crystal nuclei on Ti6Al4V, under a much higher concentration of alkaline growth solution than that for the low corrosion resistant alloys. The conversion degree of TiO2 and Al2O3 passive film to active sites increased with increasing growth solution concentration, and thereby increased the MgAl-NO3-LDHs content and reduced their lamellas size. The growth process of MgAl-NO3-LDHs on Ti6Al4V is composed of three stages: active sites formation, dense growth and sparse growth of the LDHs.

Internal defects control mechanism and process optimization of TC11 titanium alloy by cross wedge rolling

Internal defects control mechanism and process optimization of TC11 titanium alloy by cross wedge rolling

Development of a model for predicting the flash temperature in single asperity contact between TC4 titanium and Q235 steel

The friction hot surfaces generated by metal under low-speed friction is the main potential ignition source for explosive atmosphere, while the friction flash temperature is often much higher than the bulk temperature under the same conditions. Then the first to reach the ignition temperature of the combustible gas is the bulk temperature of the hot surface or the flash temperature of the contact of the asperities, which is worth studying. In view of this, by establishing a friction model, this paper conducts an in-depth study on the flash temperature of the asperities contact between the of TC4 titanium alloy and Q235 steel at the friction conditions of low speed and low load. According to the Hertz contact theory, the contact process of a single pair of asperities and the calculation method of the maximum flash temperature are analyzed, and the maximum flash temperature value is calculated using two assumptions. Combined with regression analysis, the mathematical model of the flash temperature with load and relative velocity is obtained. Under the same conditions, the maximum bulk temperature and flash temperature are calculated, so as to study the real effective ignition source of the gas at the friction conditions of low speed and low load.

Effects of heat input on microstructure evolution, mechanical and corrosion properties of TC4 alloy by keyhole TIG welding

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.

Sensitivity Study of Surface Roughness Process Parameters in Belt Grinding Titanium Alloys

In order to obtain the optimum range of process parameters for abrasive belt grinding of titanium alloys to achieve a surface roughness within a given range, titanium alloy TC4 was selected as the research object, and experiments on abrasive belt grinding surface roughness were conducted. Firstly, an empirical formula for the surface roughness of titanium alloys after abrasive belt grinding was constructed based on the balanced weight analysis of the process parameters for titanium alloy surface roughness. Sensitivity analysis was carried out to identify the process parameters with the greatest effect on surface roughness, and the stable and unstable domains of the process parameters were determined. Combined with range analysis in orthogonal experiments, the influence curves of the process parameters on surface roughness were obtained, and the optimal parameter ranges were selected. The research results showed that surface roughness is the most sensitive to changes in abrasive grain size and the least sensitive to changes in abrasive belt linear speed. The optimal ranges of abrasive grain size, abrasive belt linear speed, and grinding pressure were determined to be 120# to 150#, 15 m/s to 20 m/s, and 10 N to 15 N, respectively. This study provides a theoretical method and experimental basis for the control of surface roughness in abrasive belt grinding of titanium alloys.

Macro-electrolyte jet machining of TC4 titanium alloy using a rear-end tilt tool

Improving material removal rate and surface quality are the key issues in macro-electrolyte jet machining. The current density of the workpiece surface significantly influences material removal rate and surface quality. A novel tool with the rear-end tilted is proposed to increase the current density of the workpiece surface. The flow field simulation results demonstrate that, in comparison with standard tools, the tool with the rear-end tilted not only enables the rear-end contact with electrolyte but also enhances the rear-end electrolyte flow rate. The electric field simulation results showed that, in comparison with standard tools, the tool with the rear-end tilted enabled the rear-end to participate in the electrochemical dissolution of the workpiece surface and increased the current density of the workpiece surface. The experimental results show that the material removal rate of the workpiece is increased by 27 % and the surface roughness Ra is reduced from 6.71 μm to 2.52 μm by tools with a rear-end tilt angle of 15° compared with the standard tool. In addition, when a tool with a rear-end tilt angle of 15° is used to process the plane structure, the protrusion phenomenon of tool marks at the intersection of parallel trajectories with a step-over of 9.25 mm is the smallest, with a protrusion phenomenon of 0.092 mm.

Insight into the ignition characteristics of dust layers by mechanical friction sparks

Frictional sparks resulting from malfunctions pose a potential hazard for the accidental ignition of combustible materials in the processing industry. Ignition experiments revealed that mechanical friction sparks generated by TC4 titanium alloy, Q235 steel or 304 stainless steel were unable to ignite corn starch, PMMA, or wood powders. However, friction sparks generated by those materials at a pressure of 3.75 N/mm2 and a disc speed of 12 m/s could ignite a cotton fibrous dust layer. The release of frictional sparks is accompanied by energy dissipation. As friction pressure and rotational speed increase, the initial energy of the friction spark increases. Thus, the possibility of igniting the cotton fibrous dust layer increases, while the ignition time decreases. In terms of the ability to ignite the fibrous dust layer under identical friction conditions, the ranking is as follows: TC4 titanium alloy > Q235 steel >304 stainless steel. Moreover, TC4 friction sparks demonstrate weak ignition capability for dust layers with humidity levels of 2% and 10%. The susceptibility of the cotton fibre dust layer to ignition diminishes with increasing humidity. The distinctive flocculation structure of fibrous dust makes it more prone to ignition by mechanical friction sparks compared to traditional spherical dust. These findings imply that when employing metal alloys as mechanical equipment or tools in fibrous processing, the possibility of mechanically generated sparks serving as an ignition source should be taken into account.