TC4 Titanium Alloy Research Articles

Weld appearance, microstructure evolution and microhardness of welded joint in the TC4 additive manufactured component TIG welding

In this work, TC4 titanium alloy CMT additive thin-walled components is selected as base metal to study the weld formation, microstructure evolution, and microhardness of TIG welded joint. The results showed that the thin-walled components could obtain a good formation after TIG welding. The weld seam was mainly consisted of equiaxed and columnar of β grain. The maximum texture intensity of β phase in the weld surface was only 10.746. Therefore, there was no obvious preferred growth direction in the weld seam. The heat affected bands (HAB) in the zone of weld seam was disappeared due to the base metal no undergone multiple heating cycles after melting. In the weld cross-section and weld surface, the average hardness of base metal is about 334.5 HV and 358.8 HV, respectively. The hardness of weld seam was greater than that of the base metal. The hardness of weld surface was greater than that of weld cross-section. The change of hardness of welded joint was mainly caused by β grain size and α phase.

Microstructural evolution and tribological properties of TC6 titanium alloy strengthened by laser peening combined with nitrogen ion implantation

To obtain a combined strengthening layer and further redouble the ability to resist wear of TC6 titanium alloy, an innovative technique of laser peening plus nitrogen ion implantation was proposed. The tribological properties of the specimen subjected to combined laser peening and nitrogen ion implantation were analyzed using transmission electron microscope, nanoindentation tester, sliding friction wear tester and scanning electron microscopy. The results showed that laser peening combined with nitrogen ion implantation induced a higher density of dislocation than that produced only by laser peening or nitrogen ion implantation. Compared with the ion implanted and laser peened samples, the surface nano-hardness subjected to combined strengthening process was increased by 21.3 % and 5.8 %. Moreover, the friction coefficient of combined processed specimen reduced to 0.4, the wear tracks depth and width were about 19.02 μm and 300 μm, while the wear mechanism was mainly abrasive and oxidative wear. The dislocations, sub-grains and mechanical twins produced by laser peening provided large amounts of diffusion channels for ion implantation, which conferred better wear resistance than the samples processed only by laser peening or nitrogen ion implantation.

Excellent tribocorrosion resistance of additively manufactured Ti-based heterogeneous composite coating via hardening and toughening effects

To improve the tribocorrosion resistance of oil drill pipes used in deep-sea drilling, a Ti-based composite coating was successfully fabricated by laser direct energy deposition technology on the TC4 titanium alloy surface. The microstructure analysis showed that a new heterogeneous structure of multistage strengthening phases (micron-sized TiN phases and nano-sized TiB phases) distributed on the β matrix (soft Cu-rich phases and hard Mo-rich phases) was formed, and the size of β grain was refined to 2 μm with the content of Cu higher than 12 wt.%. The microhardness of the composite coating was increased to more than 700 HV0.2 due to the solution strengthening of Mo elements and the formation of hard TiN phases. At the same time, the fracture toughness of 12Cu composite coating was significantly increased to 8.37 MPa m1/2, which was attributed to the combined effect of grain refining, high-density dislocations in Cu-rich phases, and nanoscale TiB phases. The synergistic enhancement of hardness and toughness of 12Cu composite coating promoted the generation of titano-molybdenum-copper composite oxide film on the worn surface, and the tribocorrosion resistance increased more than 7 times compared with TC4.

Experimental and numerical investigation on high-velocity hail impact response of TC4 titanium alloy plates

This work studied the dynamic response of hail impacting on TC4 titanium alloy plates under different influence factors. Experiments were performed according to China Civil Aviation Regulations Airworthiness Standards. The damage to the plate was recorded by in-situ cameras. The experimental results indicate that the greater the hail velocity, the more severe the damage to the titanium alloy plate. In the simulation, Smoothed Particle Hydrodynamics (SPH) method was used to model the hail. The reliability of numerical model was verified by the comparison with the test results of hail impact response. The numerical results show that the deformation of the plate increases as the impact angle and hail diameter increases. Moreover, the changes in impact angle and position will both alter the displacement and strain distribution within the plate. Through comparative analysis of the impact velocity, hail diameter, impact angle, and impact position on the impact force peak, plastic strain energy, and maximum kinetic energy of the plate, it is found that changes of hail diameter and velocity have great effect on the response of titanium alloy plate, and the impact position has little effect on it. There is a power-law relationship between the hail impact peak force and the hail velocity with an index of 1.912.

Enhancing high-temperature fretting wear resistance of TC21 titanium alloys by laser cladding self-lubricating composite coatings

Fretting wear is one of the main factors restricting the fastener service reliability for the high-temperature titanium alloys. Enhancing the high-temperature fretting wear resistance of titanium alloys with laser cladding coatings is an effective method. Thus, in this work, a self-lubricating composite coating was designed and fabricated on the surface of TC21 titanium alloy with laser cladding. Special attentions were made to the effect of the fractions of the hard and self-lubricating phases on high-temperature fretting resistance. In addition, the contribution of laser cladding power was also concerned. The primary phases of the self-lubricating composite coatings are α-Co, CaF2, WC, TiC and Cr23C6, and the reasons for the formation of TiC and Cr23C6 are investigated from a thermodynamic point. The prepared composite coatings are dense and uniform. The crystallographic characteristics and the volume fractions of the hard phases (WC, TiC and Cr23C6) and self-lubricating phase (CaF2) were revealed, and the effect of grain size on the coating properties was analyzed. The hardness of the coatings were all maintained around 700 HV0.2, which was significantly higher than that of the substrate. The composite coating significantly improves the friction and wear resistance at 500 ℃. The hard phase was also found to be the most resistant to friction and wear. The frictional performance of the coating gets better when the hard phase and the self-lubricating phase increase. However, the hard phase contributes more to the high-temperature friction and wear resistance than the self-lubricating phase and the wear volume is 1/40 that of substrate. For the laser cladding power, the higher power can lead to a higher fraction of CaF2 but a lower fraction of hard phase, causing a decline in COF but an increase in wear volume. The wear mechanisms of the coating and the substrate were analyzed, the subsurface stress distribution state of the wear scars were further analyzed. The current results present new insights on the anti-wear design strategy to the composite coatings consist of hard and self-lubricating phase.

Effect of contact stress and slip amplitude on fretting fatigue behaviour of ultrasonic surface nanocrystallized TC11 titanium alloy

In this paper, combined experimental and numerical methods are applied to investigate the effect of different contact stress and slip amplitude on the fretting fatigue (FF) behaviour of TC11 titanium alloy with gradient nanostructure introduced by ultrasonic surface rolling process (USRP). The properties of gradient nanostructure are characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray residual stress tester, microhardness tester. As evidenced by the FF experimental results, USRP can significantly improve the FF life of TC11 by introducing large compressive residual stress and work hardening layer. The dominant parameters in improving the FF resistance under different loading conditions are investigated. In addition, the simulated results from Abaqus show that contact stress plays a more important role in influencing FF life compared to fretting bridge span, which is attributed to the change in slip amplitude and stress concentration. Fretting fatigue life initially increases and then decreases with contact stress and there is a contact stress threshold that leads to minimum lifetime. This threshold of USRP specimens is greater than that of untreated specimens. The transition of fretting mode along with contact stress is observed and discussed.

Effects of different treatment processes on microstructure and tensile fracture behaviour of selected laser melting TC17 titanium alloy

It is essential to study the tensile fracture mechanism of additively manufactured materials and develop the effective process treatment techniques to improve their fracture resistance. In this paper, the effects of different treatment processes on the microstructure and tensile fracture properties of TC17 titanium alloy melted by laser selective zone melting were investigated. The static tensile fracture morphological characteristics were observed by combining SEM and EDS. The metallographic microstructure after chemical corrosion was observed optically. And the tensile fracture morphology of the three states of TC17 titanium alloy samples at room temperature conditions was investigated. The results show that the metallographic matrix microstructure of TC17 titanium alloy after HT, HIP and HIP-HT treatments was a bimodal structure with α+β phases, i.e., β phase was in the form of a net basket, and α phase was in the form of a coarse bar. The grain sizes of the samples treated by different processes were different, but the difference in grain size of the HT-treated tissues was small, and the difference in grain size of the HIP-HT-treated tissues was large. And the coarse α-phase segregation could be seen at the edge of the samples. The 3D-printed materials had complex changes in anisotropic properties affected by the printing structure and tissue. The printed tissues were brittle and had high internal stresses. These problems were partly improved at high temperatures, but they still existed. The HIP-HT-treated materials had a large α+β-phase bimodal structure. The HT-treated material had coarse grains and precipitation phases, poor room temperature plasticity, and improved high temperature plasticity. After HT treatment, the original printing microstructure changed, the strength and plasticity were significantly improved, but the macroscopic printing structure still had a slight influence on the fracture morphology. When HIP treatment temperature was higher, the influence of macroscopic printing structure basically disappeared, but the grain and microstructure grew up, and the strength and plasticity were slightly lower than that of the HT treatment. HIP process basically eliminated the unfused defects of the three-dimensional morphology, and the local weak bonding zone formed.

Experimental Study on Effect of Cryogenic Treatment on Cutting Force of Titanium Alloy

Three titanium alloy materials TA7, TB6 and TC4 were selected, and three titanium alloys with different phases were placed in liquid nitrogen at -196°C for cryogenic treatment, and the change of the cutting performance of titanium alloy samples before and after cryogenic treatment was studied.Six speed combinations of 30m/min, 40m/min, 50m/min, 60m/min, 70m/min and 80m/min were selected to carry out cutting tests.The cutting experiments show that the cutting performance of TA7, TB6 and TC4 titanium alloys has been significantly improved by cryogenic treatment.At different cutting speeds, the cutting force was compared. After cryogenic treatment of three titanium alloy materials, the cutting force was reduced in machining.After cryotreatment, the cutting performance of TB6 was significantly improved, while that of TA7 was relatively low. Among them, TB6 showed the greatest improvement, followed by TA7 and TC4.The three titanium alloys without cryogenic treatment have a cutting speed of 50m/min at maximum cutting force.The maximum cutting force speed of cryogenic titanium alloy is 40m/min.

Residual stresses in linear friction welding of TC17 titanium alloy considering phase fraction

To obtain accurate residual stresses in linear friction welding of TC17 alloy, a numerical relationship between the elastic constants and phase fraction of TC17 alloy was established. The elastic constants with gradient distribution were obtained by combining the phase fraction and introduced into the contour method. The results show that the elastic constants of TC17 alloy are positively correlated with α phase fraction and present a significant gradient distribution in the welding area with a width of about 4 mm. The relative error in calculating the welding residual stresses can be up to 36.06% if the gradient distribution of phase fraction is ignored. The corrected residual stresses in the welding area exhibit a bimodal distribution, with a peak stress of ∼442 MPa located at the edge of the heat-affected zone. The results demonstrate the necessity of considering the phase fraction with gradient distribution.

Analysis of stress corrosion behaviour of TC4 titanium alloy in simulated seawater environment

Analysis of stress corrosion behaviour of TC4 titanium alloy in simulated seawater environment

Analysis of stress corrosion behaviour of TC4 titanium alloy in simulated seawater environment

Analysis of stress corrosion behaviour of TC4 titanium alloy in simulated seawater environment

Fatigue and anisotropic behavior of wire-arc additive manufactured TC17 titanium alloy

Wire-arc additive manufacturing (WAAM) was used in aeronautical engineering due to its low equipment cost and ability to create complex shapes. However, the fatigue behavior of WAAM titanium alloy, specifically for low cycle fatigue (LCF), was poorly studied. This paper investigated the microstructure and mechanical behavior of WAAM TC17 in both vertical and horizontal orientations. Fully reversed LCF tests were conducted on specimens with varying strain amplitudes from ±0.4 % to ±1.2 %. The results found that the ultimate tensile and yield strength were similar for both vertical and horizontal samples, but the elongation in the horizontal orientation was approximately 60 % lower than that in the vertical orientation. Considering the cyclic loading behavior, both vertical and horizontal samples exhibited cyclic softening characteristics at high strain amplitudes (0.8%–1.2 %). Additionally, the cyclic softening rate (CSR) of horizontal samples exhibited a higher than that of vertical samples at high strain amplitude. The LCF cracks of WAAM TC17 were initiated from the surface and internal defects of the samples. The LCF performance of the horizontal samples was found to decrease than that of vertical samples. Specifically, the fatigue performance of the horizontal samples is lower by 36.7 % compared to the vertical samples when the number of cycles is 103.

Simple fabrication of anisotropic slippery lubricant-infused surface for directional transportation and anti-corrosion by metal-metal laminated composites

Slippery lubricant-infused surfaces with anisotropy for directional transportation have been widely researched and fabricated. However, the preparation of the required surface morphology remains complex and challenging. Inspired by the laminated structure found on natural shell nacre and slippery characteristics of nepenthes, a simple and universal method was provided to fabricate anisotropic slippery lubricant-infused surface. 304/TC4 metal-metal laminated composites were prepared by diffusion bonding 304 stainless steel and TC4 titanium alloy foils. A regular micro array with grooves was obtained through simple chemical etching. The widths of grooves and bulges, as well as the depths of grooves could be adjusted as needed. After the chemical modification, the lubricant was infused into grooves to obtain anisotropic slippery lubricant-infused surfaces. The directional transportations along the grooves of water droplet in air and bubbles underwater were achieved on the fabricated surfaces. Furthermore, the achieved surfaces demonstrated outstanding performance in anti-corrosion and anti-fouling. A noteworthy advantage of using laminated composites to fabricate anisotropic slippery lubricant-infused surfaces lies in its simplicity, universality, and repeatability. Based on the previous reports about laminated composites, the structure with grooves can been obtained by simple chemical etching. This method is suitable for various materials, including metal, ceramic, carbon material, and polymers. It has great potential application in water collection, directional transportations, anti-corrosion and anti-fouling.

Optimization of the hot stretch-bending process for TC4 titanium L-section profile

Titanium alloys are used more and more in the field of aerospace because of their low weight and high strength. Compared with pure bending, stretch-bending can effectively reduce springback and improve forming accuracy, and is widely used in the forming of high-quality profile structural parts. In this study, based on the loading method of the arm-type stretch-bending machine, the hot stretch-bending process of the TC4 titanium alloy profile with L-shaped section was simulated by ABAQUS. The effects of profile temperature, tension, and section size on the stretch-bending results were analyzed, and the process parameters were optimized. The experimental verification was carried out on the self-designed hot stretch-bending test machine, and the relative deviation between the experiments and simulations is within 1%. This study has guiding significance for the setting of process parameters of hot stretch-bending of titanium alloy profiles.

Effects of Pulsed Current on the Microstructure and Properties of Laser Cladded TC17 Titanium Alloy.

In this study, a titanium alloy substrate was cladded with TC17 titanium alloy powder using the pulsed-current (PC)-assisted laser cladding technique. The primary objective of this research was to assess the impact of varying pulsed current intensities on the morphology, microstructure, and properties of samples. It is observed that the utilization of pulsed currents significantly enhances the metallurgical adhesion between the samples, concurrently diminishing the occurrence of porosity within the cladding layer. The incorporation of a pulsed current also has a positive impact on the microhardness and corrosion resistance of the samples. Furthermore, the synergistic influence of laser energy and a pulsed electrical current is found to promote a structural evolution in materials towards a state with lower electrical resistance. The introduction of a pulsed current leads to preferential growth of β grains with <100>// cladding direction in the cladding zone and obtains the typical {100} < 001 > cube texture, while the substrate zone exhibits a distinctive stripe-like configuration formed by the primary α-phase constituents. The outcomes of this study show the pivotal role of pulsed currents as an auxiliary technique for enhancing the properties and effecting microstructural modifications in titanium alloys during the laser cladding process.

Electron beam weldability of TiZrNbTa refractory high-entropy alloy and TC4 titanium alloy

Welding is a crucial process for the application of new materials in engineering. By welding refractory high-entropy alloys with other alloys, a composite structure can be formed that not only combines the advantages of both materials but also reduces costs. This paper focuses on evaluating the electron beam weldability of TiZrNbTa refractory high-entropy alloy. Additionally, it presents an innovative approach to achieve dissimilar electron beam welding of TiZrNbTa and TC4 titanium alloy, resulting in defect-free welded joints. The microstructure of the two groups of welds was analyzed, and the relationship between microstructure evolution and the mechanical properties of the joint was studied. The microstructure characterization of the two sets of welds was carried out after welding, and the relationship between the weld tissue evolution and the mechanical properties of the joints was investigated. It was found that the grains in the fusion zone of TiZrNbTa were significantly refined and the casting holes were significantly reduced. Although macroscopic segregation was found in the dissimilar welds, the subsequent tensile tests revealed a 10% increase in tensile strength over TiZrNbTa at 389 MPa. In addition, the dissimilar joints exhibited excellent compression strength and compressive yield strain (1280 MPa, 23.5%). However, both had poor tensile plasticity, a typical brittle fracture mode, and the fracture occurred on the TiZrNbTa parent material side, and the reason for the fracture was explained. This study confirms for the first time the good weldability of TiZrNbTa and TC4 titanium alloy, which provides theoretical support for the engineering application of refractory high-entropy alloys.

A method for preparing alloy coating on the aluminum alloy substrate via laser cladding technology to prevent the galvanic corrosion of TC4/5083 couple

The Cu-Ni-Cr alloy coating was prepared on 5083 aluminum alloy substrate using laser cladding technology. The microstructure of the coating and its galvanic corrosion resistance in contact with TC4 alloy were studied. The results indicate that the Cu-Ni-Cr alloy coating primarily consists of Al-rich dendrite phase and Cu-rich matrix phase. The shear strength of the Cu-Ni-Cr alloy coating is 154.68 MPa, which is greater than that of the aluminum alloy substrate. The galvanic current density of the TC4/Cu-Ni-Cr couple is 0.05 μA·cm−2. The neutral salt spray corrosion test results demonstrate that the Cu-Ni-Cr alloy coating exhibits excellent resistance to galvanic corrosion. The coating can attenuate the galvanic corrosion effect when it is in contact with the TC4 titanium alloy, offering new solutions to address the galvanic corrosion challenges between titanium alloy and aluminum alloy in marine environments.

Constitutive relationship and fracture mechanism for wide stress triaxiality of titanium alloy

It is necessary to determine the fracture criteria and parameters that conform to the plastic deformation and fracture mechanism of titanium alloy under wide stress triaxility. Fourteen different shapes and notch specimens were designed for uniaxial tensile and compression experiments. Based on the analysis of plastic behavior and fracture mechanism, the Swift-Voce hardening model, CPB06 yield criterion and DF2016 fracture criterion were respectively established. The fracture parameters of the ductile fracture model were calculated by the analytic equation solving method. The fracture behavior of forged TC4 titanium alloy was successfully predicted by finite element software. The research results showed that the dimples of fracture morphology become larger and deeper with the increase of stress triaxiality, and the ductile fracture mechanism changes from shear fracture to dimple fracture mechanism. The comparison of experiment and simulation indicated that the Swift-Voce hardening model and CPB06 yield criterion reasonably simulate the plastic deformation. It also proved the DF2016 model can provide the most accurate prediction of fracture behavior for forged TC4 alloy under different stress states.

Microstructure and pore sensitivities in very high cycle fatigue behaviors of titanium alloy welded joints under stress ratios

Very high cycle fatigue behavior of electron beam welded TC17 titanium alloy joints under different stress ratios was investigated. The results revealed that the welded joints exhibited different failure modes depending on the stress ratios applied. As the stress ratio increased, the failure probability attributed to welded pores in the fusion zone (FZ) gradually decreased, shifting the failure mode towards fatigue failure induced by the primary α phase in the base metal (BM). Moreover, the stress intensity factor at the edge of fine granular area (FGA) was determined to be the threshold of long crack growth. It was observed that the size of the plastic zone at the crack tip of FGA was related to the acicular α phase structures precipitated through recrystallization in the FZ. The influence of effective size and location of welded pores on fatigue life was further discussed. To gain further insights, improvements were made to the K-T diagram. Consequently, the non-crack propagation zone and the critical safety size of welded pores responsible for initiating cracks in the welded joint were identified. Additionally, the Weibull probability function was employed to determine the average size of welded pores that led to fatigue failure in the welded joints.

The microstructure and impact toughness of vacuum electron beam welded joints of a highly alloyed dual phase titanium alloy

Vacuum electron beam welding of 50 mm thick TC18 titanium alloy plates were carried out at different processing parameters, and full penetration welded joints were obtained. The welded joint presents three typical zones, namely, fusion zone, heat affected zone and base metal zone. It is found that processing parameters have no obvious influence on the width of heat affected zone. By using EBSD technology, the changes of phase composition, grain size and grain boundary density from the fusion zone to heat affected zone and then to base metal zone were clearly observed and quantitatively analyzed. The fusion zone shows coarse equiaxed/columnar β grains with an average diameter/width of more than 100 μm. The volume fraction of α phase in the heat affected zone decreases with the decrease of the distance to the fusion zone until it is completely dissolved into β phase. The formation mechanism of microstructure in different zones and its influence on impact toughness were discussed. The β grain size and undissolved/precipitated fine α grain on β grain boundary are two main factors affecting impact toughness.