TC4 Alloy Research Articles

Response of NiCrAl-bentonite abradable seal coatings to thermal/salt corrosion

The growing need for engine services in marine environments has resulted in increasing salt and coupled corrosion of abradable seal coatings (ASCs). In this study, the response of NiCrAl-bentonite ASCs to thermal/salt corrosion was assessed. The results indicated that NiCrAl-bentonite ASCs could provide excellent protection for TC4 alloys in marine environments. NiCrAl-bentonite ASCs retained their low hardness and high strength and exhibited good abradability in chloride-rich environments. Compared with the Al-, Ni-, and YSZ-based coatings, the proposed coating demonstrated improved synergy between strength and hardness/abradability. This research provides valuable insights into the reliable use of NiCrAl-bentonite ASCs in marine environments.

High-temperature wear resistance improvement mechanism of TiAlCrNiSiNbx high-entropy alloy films through sliding wear-induced gradient nanostructure

TiAlCrNiSiNbx high-entropy alloy films (HEFs) with varying Nb concentrations were deposited using multi-target magnetron co-sputtering at a controlled sputtering power. At room temperature (RT), 300 ℃, 500 ℃ and 700 ℃, the average coefficients of friction (COF) and wear rates of TiAlCrNiSNbx HEFs were lower than those of TC4 alloy. TiAlCrNiSiNbx HEF with a Nb content of 12.36 at% exhibited the best wear resistance at 700 ℃. A nanocomposite layer (∼260 nm) and a plastic deformation region (∼1.2 µm) formed on the film during the wear at 700 ℃. The Al2O3, Cr2O3, SiO2, and Nb2O5 in the nanocomposite layer facilitated the formation of a dense oxide layer. The cooperative deformation effect of nanocrystalline metal oxides and amorphous phases is conducive for inhibiting strain localization and enhancing wear resistance. The grain size of the nanocomposite layer was significantly refined, with an average size of 3.98 nm. This was attributed to the grain refinement caused by the interaction of dislocations and deformation twins in the plastic deformation region, which improved the strength and hardness of the film. The gradient nanostructure of the nanocomposite layer and plastic deformation region led to a more homogeneous plastic deformation, effective inhibition of strain localization and suppression of the micro-crack.

Effect of sputtering time on the microstructure and properties of MAO/CoCrFeNi composite coatings on TC11 alloy

In order to further improve the wear resistance and high-temperature oxidation resistance of titanium alloys, MAO/CoCrFeNi composite coatings with different sputtering times were prepared on TC11 alloy by micro-arc oxidation combined with radio frequency magnetron sputtering. The microstructure and phase composition of the composite coatings were investigated by scanning electron microscope and X-ray diffractometer. The wear performance at different temperature and high-temperature oxidation resistance of the composite coatings were studied. The results showed that as the sputtering time increases, the phase structure of composite coatings were all FCC phase, and the number of micropore on the composite coatings decreased; At room temperature, since the film thickness is proportional to the hardness, and higher hardness is conducive to the reduction of actual contact area between coating and grinding ball, so the composite coatings sputtered for 6 h had the narrowest wear scar width and the smallest wear weight loss, and its wear mechanisms were oxidative wear and adhesive wear; At 673 K, since the softening of the abrasive chips played a lubricating role, the composite coatings sputtered for 4 h produced the most abrasive chips, so it had the narrowest wear scar width and the smallest wear weight loss, and the wear mechanisms were mainly oxidative wear and adhesive wear, with slight abrasive wear; The composite coatings sputtered for 6 h was still tightly bonded to the substrate after oxidation at 1000 K, and its weight gain is smaller than TC11, which indicated that it has the best high-temperature oxidation resistance.

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.

Enhancing the wearing resistance of TC17 alloy by nano/micro-TiC ceramic through directed energy deposition

Micro-TiC (m-TiC), nano-TiC (n-TiC), and nano/micro-TiC (n/m-TiC) ceramic particles reinforced TC17 composites were prepared using directed energy deposition (DED) technology. The microstructure, microhardness and wear properties of the composites were systematically studied. Under the same conditions, m-TiC partially melted, while n-TiC fully melted. The varying degrees of melting resulted in differences in both the level of grain refinement and the in-situ TiCX morphologies. The average grain sizes of the TC17 alloy, m-TiC/TC17, n-TiC/TC17, and n/m-TiC/TC17 composites are 76.96 μm, 39.43 μm, 20.76 μm, and 21.32 μm, respectively. The n-TiC demonstrated a superior grain refinement effect compared to m-TiC. The m-TiC/TC17 composite precipitated diverse small primary and eutectic TiCX. The n-TiC/TC17 and n/m-TiC/TC17 composites were mainly composed of primary dendritic and rod-like TiCX, with no eutectic phases observed. The n/m-TiC/TC17 composite showed the highest hardness (∼ 579.417 HV0.2) and best wear resistance (0.0592 mg/m), with a 44.4% hardness increase and a 51.4% wear rate decrease compared to TC17 alloy. In contrast, m-TiC/TC17 and n-TiC/TC17 composites showed hardness increases of 4.55% and 35.99%, and wear rate reductions of 18.7% and 43%, respectively.

Effect of NdCl3 on characteristics of micro-arc oxidation coating formed on TC4 alloy

Effect of NdCl3 on characteristics of micro-arc oxidation coating formed on TC4 alloy

Correlation Between Microstructure and Tensile Properties in TC18 Alloy with Lamella Structure

Correlation Between Microstructure and Tensile Properties in TC18 Alloy with Lamella Structure

Influence of interfacial micro-textures on CFRTP-TC4 hybrid joint formation with laser assistant joining technique

To investigate the influence of interfacial micro-textures on the carbon fiber reinforced thermoplastic composites (CFRTP)-TC4 alloy hybrid joint formation process, a finite element model with micro-textures was established. The joint formation mechanism and the impact of joining parameters on heat input were analyzed. The results show that the existence of interfacial micro-textures will lead to an uneven distribution of the temperature field on the surface of polyamide and reduce the heat transferred to the surface of CFRTP. And, mechanical interlocks and new chemical bonds are generated in the joining process because of these micro-textures, which enhances the joining strengthen significantly. The optimized joining parameter window was also obtained and the joining strength was predicted by numerical simulation. With the numerical assistant, the CFRTP-TC4 joint with highest shear strength was obtained as the laser power and the welding speed is 130 W and of 2 mm/s, respectively.

Experimental Study of Performance of Ti-6Al-4V Femoral Implants Using Selective Laser Melting (SLM) Methodology

Selective laser melting (SLM) technology used for the design and production of porous implants can successfully address the issues of stress shielding and aseptic loosening associated with the use of solid implants in the human body. In this paper, orthogonal experiments were used to optimize the process parameters for SLM molding of Ti-6Al-4V (TC4) material to investigate the effects of the process parameters on the densities, microscopic morphology, and roughness, and to determine the optimal process parameters using the roughness as a judging criterion. Based on the optimized process parameters, the mechanical properties of SLM-formed TC4 alloy specimens are investigated experimentally in this paper. The main conclusions are as follows: the optimal combination of roughness is obtained by polar analysis, the microhardness of SLM-molded TC4 alloy molded specimens is more uniform, the microhardness of specimens on the side and the front as well as the abrasion resistance is higher than that of casting specimens, the yield strength and tensile strength of specimens is higher than that of ASTM F136 standard and casting standard but the elongation is not as good as that of the standard, and the elasticity and compressive strength of porous specimens are higher than that of casting specimens at different volume fractions. The modulus of elasticity and compressive strength are within the range of human skeletal requirements. This work makes it possible to fabricate high-performance porous femoral joint implants from TC4 alloy SLM-molded materials.

Influences of solution temperature on microstructures and performance of electron beam welded joints of laser powder bed fusion TC11 thin-walled samples

The effects of subtransus treatment (750 °C, 800 °C, 850 °C, 900 °C, and 950 °C) as well as supertransus treatment (1100 °C) on the microstructures and mechanical performance of electron beam welded (EBW) joints of laser powder bed fusion (LPBF) TC11 alloy were investigated. At a solution temperature of 950 °C, globular α phases and transformed β phases were observed in the joint. When the solution temperature exceeded the β transus temperature (Tβ), α colonies and massive α phases emerged in the joints, resulting in Widmanstatten structures. The base metal (BM) exhibited the highest microhardness, followed by the heat affected zone (HAZ), whereas the fusion zone (FZ) demonstrated the lowest microhardness. As the solution temperature increases, the microhardness of joints decreases at first and then increases. Notably, the joint subjected to a solution temperature of 850 °C exhibited the lowest microhardness. When the solution temperature was ≥900 °C, transformed β phases emerged within the joints, resulting in an elevation of microhardness. Below Tβ, the elongation of welded joints gradually augmented while the tensile strength reduced at first and then increased with the rising solution temperature. Microstructures in joint with solution temperature of 950 °C consisted of lamellar α phases, globular α phases, and transformed β phases. As a result, the joint exhibited an optimal balance between strength (1103.1 ± 34.9 MPa) and plasticity (9.37 ± 0.20%). Ductile fracture characteristics with dimples on the fracture surface were observed in the tensile samples. Therefore, it can be concluded that a solid solution temperature of 950 °C is optimal for LPBF TC11 alloy.

Nanocrystalline Ti‐Al‐Mo‐Zr‐Si Alloy (TC11) by Laser Powder Bed Fusion In‐situ Alloying

TC11 alloy is an important high temperate Ti alloy. Its laser in‐situ alloying by powder bed fusion‐laser beam (PBF‐LB) has been explored in this study. Results show that it is feasible to print the TC11 alloy using elemental powders rather than pre‐alloyed powder, in terms of high density and good combination of strength and ductility at both room and elevated temperatures, along with minor loss of composing elements. Interestingly, it is noticed that an unusual nanocrystalline microstructure has formed due to the use of ZrH2 powder feedstock, partially explaining the reason for the good mechanical properties achieved. Finite element analysis has been employed to understand the in‐situ alloying. Furthermore, a post processing by micro‐arc oxidation (MAO) has been employed to the alloy, aiming to enhance its high‐temperature oxidation resistance. The results make an implication that hydrides such as ZrH2 may hold the promise to develop nanosized, advanced Ti materials through laser in‐situ alloying, and MAO can be considered for PBF‐LB prepared TC11 alloy.

Enhanced interfacial bonding strength of hot-pressed titanium Alloy/CFRTP joint via laser ablation and interfacial adhesive

Joining titanium alloy with carbon fiber reinforced thermoplastic (CFRTP) is one of the hot subjects in the automotive and aerospace industries. To improve the joint strength of TC4/CFRTP PA6, this study combined the surface treatment of TC4 alloy, including laser ablation, Silane Coupling Agent (SCA) treatment, and interfacial PA6 adhesive. The results showed that the pretreatment and the laser texturing induced the micro-scale porous and macro-scale groove grid structure, respectively. The superhydrophilicity of the laser texturing as well as amino polar groups induced by SCA treatment promoted the adhesion of the thermoplastic PA6 melt into the microstructure of the TC4 alloy surface. The mechanical interlocking and hydrogen bonding between TC4 alloy and CFRTP PA6 significantly improved the shear strength of the TC4/CFRTP PA6 joint (17.5 MPa). Furthermore, with the incorporation of interfacial PA6 adhesive, the joint strength was further enhanced, and the damage of the TC4/CFRTP PA6 joint was transformed from interfacial to interlaminar CFRTP PA6.

Corrosion and Biological Behaviors of Biomedical Ti-24Nb-4Zr-8Sn Alloy under an Oxidative Stress Microenvironment.

Biomaterials can induce an inflammatory response in surrounding tissues after implantation, generating and releasing reactive oxygen species (ROS), such as hydrogen peroxide (H2O2). The excessive accumulation of ROS may create a microenvironment with high levels of oxidative stress (OS), which subsequently accelerates the degradation of the passive film on the surface of titanium (Ti) alloys and affects their biological activity. The immunomodulatory role of macrophages in biomaterial osteogenesis under OS is unknown. This study aimed to explore the corrosion behavior and bone formation of Ti implants under an OS microenvironment. In this study, the corrosion resistance and osteoinduction capabilities in normal and OS conditions of the Ti-24Nb-4Zr-8Sn (wt %, Ti2448) were assessed. Electrochemical impedance spectroscopy analysis indicated that the Ti2448 alloy exhibited superior corrosion resistance on exposure to excessive ROS compared to the Ti-6Al-4V (TC4) alloy. This can be attributed to the formation of the TiO2 and Nb2O5 passive films, which mitigated the adverse effects of OS. In vitro MC3T3-E1 cell experiments revealed that the Ti2448 alloy exhibited good biocompatibility in the OS microenvironment, whereas the osteogenic differentiation level was comparable to that of the TC4 alloy. The Ti2448 alloy significantly alleviates intercellular ROS levels, inducing a higher proportion of M2 phenotypes (52.7%) under OS. Ti2448 alloy significantly promoted the expression of the anti-inflammatory cytokine, interleukin 10 (IL-10), and osteoblast-related cytokines, bone morphogenetic protein 2 (BMP-2), which relatively increased by 26.9 and 31.4%, respectively, compared to TC4 alloy. The Ti2448 alloy provides a favorable osteoimmune environment and significantly promotes the proliferation and differentiation of osteoblasts in vitro compared to the TC4 alloy. Ultimately, the Ti2448 alloy demonstrated excellent corrosion resistance and immunomodulatory properties in an OS microenvironment, providing valuable insights into potential clinical applications as implants to repair bone tissue defects.

Effect of Preheating and Post-Heating on the Microstructures and Mechanical Properties of TC17-Ti2AlNb Joint with Electron Beam Welding.

To enhance welding quality and performance, preheating and post-heating are usually employed on high-temperature materials, concurrently with welding. This is a novel technique in vacuum chamber electron beam welding (EBW). TC17 and Ti2AlNb alloys are the hot topics in aero-engine parts, and the welding of dissimilar materials is also a broad prospect. To settle welding cracks of Ti2AlNb, EBW with preheating and post-heating was investigated on TC17 and Ti2AlNb dissimilar alloy, which improved the manufacturing technology on high-temperature materials. The dissimilar joint no longer had cracks after preheating, which exhibited excellent welding stability and metallurgical homogeneity, and preheating and annealing had an important effect on mechanical properties. The joint strength after 630 °C annealing is higher than that of TC17 alloy base metal (BM) and other annealing temperatures, reaching 1169 MPa at room temperature and 894 MPa at 450 °C tensile condition. The joint plasticity after 740 °C annealing is equivalent to TC17 BM. EBW with preheating improved the microstructure characteristics and enhanced the plasticity of Ti2AlNb alloy weld and dissimilar joint, which would contribute to the application of Ti2AlNb alloy and Ti2AlNb dissimilar parts.

Tribological behaviour of polytetrafluoroethylene containing plasma electrolytic oxidation coatings on TC4 alloy

Improving the tribological performance of titanium alloys is crucial to expanding their industrial applications. In this study, self-lubricating and wear-resistant coatings for TC4 alloy were achieved by combining plasma electrolytic oxidation (PEO) prepared using compounded electrolytes with incorporation of polytetrafluoroethylene (PTFE) as a solid lubricant. The investigation focused on the comprehensive effects of compounded electrolytes and PTFE on the microstructure and tribological behaviour of PEO coatings. After doping with PTFE, the coating prepared in electrolyte containing silicate, phosphate, and aluminate exhibited lowest wear rate (decreasing by 95.1%) and maximum hardness of 638.6 HV compared to other coatings. Additionally, the coefficient of friction (COF) significantly decreased from 0.8 to 0.16. This can be attributed to the strategy of depositing low-frictional discontinuous layers on hard PEO coatings.

Study on the tribological characteristics of surface triangular textured TC4 alloy prepared by SLM technology

Surface Triangular Textured TC4 Alloy specimens were prepared by 3D printing technology (SLM technology: selective laser fusion). Effects of wedge-shaped triangular textures with different texture area occupancy on hardness, friction and wear of the 3D printed TC4 alloy specimens were studied, in comparison with non- textured specimens. SFT -2 M pin-disc friction and wear testing machine was used to perform friction and wear experiments under 46 # mechanical oil lubrication conditions, and MH-500 Vickers hardness tester was used to measure hardness of the specimens. Scanning electron microscope (SEM), energy spectrometer (EDS), and electronic balance instrument were used to characterize the wear scar morphology, element content, wear amount, etc. of the specimens. Using the Fluent module in ANSYS Workbench software, we studied the mechanism for the reduction in the friction coefficient between friction pairs during the relative movement in lubricating oil. Results of the study show that the hardness of the 3D printing specimen is significantly greater than that of the non- textured one. In each group of experiments, the wedge triangular textured specimens showed better tribological properties, and the 3D printed specimen with an area occupancy of 22. 53 % exhibited the smallest average friction coefficient (0.17) and higher wear resistance than other specimens. The dynamic pressure effect due to the wedge triangle texture inside the lubricating oil film is the main reason for the reduced friction coefficient between the friction pairs.

Effect of Ti3AlC2 particles on microstructure and tribological properties of micro-arc oxidation layer on TC4 alloy

TiO2 metal oxide layers rich in Ti3AlC2 phase was successfully prepared on TC4 alloy by micro-arc oxidation (PECC or ASD) process. Analysis of the material phases contained in the PECC layer by X-ray diffractometry; scanning electron microscopy and energy spectroscopy were used to analyses the pores and elemental distribution on the surface of the specimens; the cross-sectional thickness of PECC layers were measured by metallographic microscope; confocal microscopy was used to measure the surface roughness of the sample; High temperature wear resistance of PECC layers with different Ti3AlC2 concentration was compared by tribological wear testing. The results show: 1) The incorporation of Ti3AlC2 particles plays an obvious catalytic role in the growth of PECC layer and the thickness is up to 74.74 μm; 2) When the concentration of Ti3AlC2 gradually increases, the PECC layers fluctuates obviously, and the deposition sealing effect is remarkable; 3) When the concentration is 4-6 g/L, the alloy has the best wear resistance, volume wear is only 1.98×10-4 mm3 /N·m. Experiments have shown that surface modification of the alloy using the PECC process can further broaden the application of the alloy in the field of anti-wear

Fabrication of robust superhydrophobic surface on TC4 alloy by wire electrical discharge machining

Superhydrophobic metal surfaces have significant applications in various areas such as surface self-cleaning, resistance reduction, anti-corrosion, etc. However, inexpensive preparation methods for superhydrophobic surfaces with a good mechanical stability are still to be developed. In this study, microarray structures on TC4 alloy were readily fabricated using a wire electrical discharge machining technology. Following the treatment with a fluorinating reagent, the microarray surface exhibited excellent superhydrophobic properties, where the largest contact angle and the smallest sliding angle reached 159° and 3°, respectively. Influences of the dimensions of microarray structure on the TC4 alloy surface wettability were also investigated in this study. Experiments show that this superhydrophobic surface possesses favorable self-cleaning, good mechanical stability, and promising anti-corrosion properties. In addition, by controlling the dimensions of the microstructure a superhydrophobic surface with a gradient wettability was also fabricated, which exhibits the property of doing nondestructive transportation of liquids.

Microstructure and Wear Resistance of Grx-Ti-BN Composite Coating on TC4 by Argon Arc Cladding

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.

Microstructure and Impact Toughness of Laser-Arc Hybrid Welded Joint of Medium-Thick TC4 Titanium Alloy

This study delves into the impact toughness of medium-thick (12 mm thick) titanium alloy joints crafted through a multi-layer, multi-pass welding technique that blends laser-arc (MIG) hybrid welding technology. Microstructural scrutiny, employing optical microscopy, SEM and TEM, unveils a consistent composition across weld passes, with prevailing α/α′ phases interspersed with some β phase, resulting in basket-weave structures primarily dominated by acicular α′ martensite. However, upper regions exhibit Widmanstatten microstructures, potentially undermining joint toughness. Hardness testing indicates higher values in cosmetic layers (~420 HV) compared to backing layers and bending tests manifest superior toughness in lower joint regions, attributed to smaller grain sizes induced by repetitive welding thermal cycles. Impact toughness assessment unveils diminished values in the weld metal (WM) compared to the heat-affected zone (HAZ) and base material (BM), amounting to 91.3% of the base metal’s absorption energy. This decrement is ascribed to heightened porosity in upper regions and variations in grain size and phase composition due to multi-layer, multi-pass welding. Microstructural analysis proximal to failure sites suggests one mechanism wherein crack propagation is impeded by the β phase at acute crack angles. In essence, this study not only underscores the practicality of laser-MIG hybrid welding for medium-thick TC4 alloy plates but also underscores the reliability of joint mechanical properties.