Titanium Alloy Ti Research Articles

Surface softening mechanism based on microstructure analyses under ultrasonic impact condition for Ti-17 titanium alloy

Surface softening mechanism based on microstructure analyses under ultrasonic impact condition for Ti-17 titanium alloy

Fatigue properties of a Ti–5Al–5Mo-5 V–3Cr alloy manufactured by electron beam powder bed fusion

AbstractAdditive manufacturing (AM) is a modern way of manufacturing structures, which tends to have fewer design limitations than those manufactured by conventional processes such as casting or forging. A combination of high-strength materials and small and complex structures opens up a wide range of potential applications, especially in the fields of medicine and aerospace. Titanium and its alloys show a very beneficial combination of density and mechanical properties. One of these alloys is the metastable β titanium alloy Ti– 5Al–5Mo–5 V–3Cr (Ti-5553), which is currently used mainly for large forged structures like landing gears of airplanes. In this study, for the first time the fatigue behavior of electron beam powder bed fused (PBF-EB) Ti-5553 was investigated with a focus on the defects created by the layer wise manufacturing. To understand the defect structure and its respective influence on the fatigue behavior, all specimens were scanned prior to fatigue testing using a state-of-the-art µ-focus CT. The specimens were subjected to two heat treatment procedures commonly used in technical applications, which were aiming for high strength (solution treated and aged—STA) as well as high ductility (beta annealed, slow cooled and aged—BASCA). Results indicate that the fatigue strength of PBF-EB manufactured Ti-5553 is significantly reduced compared to conventionally manufactured Ti-5553. The main reason for this are defects, which have varying critical effects depending on the heat treatment of the specimen and the defect size, shape, location and type.

Effects of solution treatment on microstructure and properties of Ti-5.7Al-3.9Sn-0.91Mo-3.4Zr-0.40Si-0.38Nb-0.95Ta titanium alloy

This study investigated the effects of solution treatments under various conditions on the matrix and silicides microstructure and their impact on the mechanical properties of high-temperature Ti60 (Ti-5.7Al-3.9Sn-0.91Mo-3.4Zr-0.40Si-0.38Nb-0.95Ta) titanium alloy. The microstructure evolution during solution treatments was characterized, and the tensile properties at 600 °C and room temperature (RT) were investigated. The results show that the fraction and grain size of martensite and silicides can be tailored through solution treatments. With increasing solution temperature, the fraction of primary α (αp) phase and silicides decreases, while that of the transformed β (βt) microstructure increases. After solution treatment at 1025 °C, the yield strength (YS) and ultimate tensile strength (UTS) reach 685.0 MPa and 900.8 MPa, respectively, at 600 °C, increasing by 18.0% and 27.0%, respectively, compared to the initial state. The elongation (EL) remains at 16.2%. The strengthening mechanisms of Ti60 alloy include grain boundary strengthening of the αp phase and martensite formed during rapid cooling, as well as precipitation strengthening of the silicides. With increasing solution temperature from 950 °C to 1025 °C, the fraction of martensite strengthening increases from 38.4% to 89.3%, while the fraction of precipitation strengthening of silicides decreases from 3.63% to 1.17%.

Comparison of misfit and roughness of CAD-CAM ZrO, selective laser sintered CoCr and preformed Ti implant abutment crowns

BackgroundMarginal misfit and surface roughness of customized implant abutments is critical for restorative success. However, little is known about the comparison of misfit and surface roughness of CAD-CAM Zirconium oxide (ZrO), selective laser melting (SLM) Cobalt Chrome (CoCr) and preformed abutments. The aim of the study is to investigate the relation of misfit and micro-roughness of selective laser melting (SLM), preformed and CAD-CAM implant abutments.MethodsThirty internal connection, endosseous dental implants (Ø 4.0 mm x 10 mm, Dentium) were mounted in Polymethyl methacrylate vertically. Ten preformed Titanium alloy (Ti) abutments with 1 mm soft tissue height and Ø 4.5 mm were included as controls. Ten each of Y-TZP and SLM-CoCr, abutment/crowns were fabricated using CAD-CAM milling (CAD-CAM-ZrO) and SLM techniques. Surface micro-roughness (Ra) of the fabricated implant abutment/crown was evaluated with a 3D optical non-contact microscope. All implant restorations were torqued to implants (30 Ncm) using a Tohnichi BTGE digital torque gauge and were analyzed with Bruker micro-CT (Skyscan 1173) to detect micro-gaps at pre-selected points at implant abutment interface. The Ra and misfit data were compared using ANOVA, Tukey-Kramer, Kruskal-Wallis test and Pearson correlation (p < 0.05).ResultsMean Ra among SLM CoCr abutments [0.88 (0.09) µm] were lower than CAD-CAM-ZrO and higher than preformed Ti abutments. Horizontal misfit among SLM-CoCr [45.43 (9.41) µm] and preformed Ti [36.87 (13.23) µm] abutments was not statistically different (p > 0.05). Misfit was significantly higher in Y-TZP samples compared to SLM-CoCr (p = 0.031) and preformed Ti abutments (p = 0.01). Preformed Ti abutments showed significantly lower misfit compared to SLM-CoCr abutments (p = 0.01). A positive linear correlation was observed between the surface roughness (Ra) and vertical misfit (r = 0.61, p < 0.05).ConclusionSLM CoCr abutments showed rough surface compared to preformed Ti abutments, while horizontal misfit was comparable among SLM-CoCr and preformed abutments. Misfit was significantly greater in Y-TZP abutments, compared to SLM and preformed abutments. SLM abutment fabrication technique needs further improvement to provide better fit and surface topography.

Optimization of Machining Process on Coated Tungsten Carbide Electrode Tool and Titanium Alloy Workpiece Using EDM: A Critical Review

Commercial applications for Ti 6Al 4V, an alloy composed of titanium, aluminium, and vanadium, are possible. The features of titanium alloy include: Lightweight, non-magnetic, high melting point, outstanding fatigue strength, superior specific strength, great corrosion resistance, and biocompatibility. Reviewing the electro-discharge machining of titanium alloy (Ti 6Al 4V) as a workpiece, silicon carbide particle combined with EDM oil, and coated tungsten carbide electrode, this research examines this process. Dielectric fluid's impact on microhardness, surface finishing, TWR, and MRR. MRR is raised by silicon particles and coated tungsten carbide electrodes with EDM fluid. According to the study, the most important input parameters for determining TWR, MRR, surface finishing, and micro-hardness are voltage, current, pulse on time (Tonne), and pulse off time (Toff).

Determination of Cast-Metal Structures and Welded Joints After Electron-Beam Welding of the Intermetallic Titanium Alloys Ti−28Al−7Nb−2Mo−2Cr Obtained by Electron-Beam Melting Method

Determination of Cast-Metal Structures and Welded Joints After Electron-Beam Welding of the Intermetallic Titanium Alloys Ti−28Al−7Nb−2Mo−2Cr Obtained by Electron-Beam Melting Method

Hot Forgeability of Titanium Alloy Ti–6Al–2.2Mo–1.4Cr–0.4Fe–0.3Si Alloy: An Approach Using Processing Map

Hot Forgeability of Titanium Alloy Ti–6Al–2.2Mo–1.4Cr–0.4Fe–0.3Si Alloy: An Approach Using Processing Map

Tuning interfacial mechanical properties of Ti/CFRP laminates using customized intercalation of woven metallic fabrics

Improving the interlaminar fracture toughness of fiber metal laminates comprising titanium alloy (Ti) and carbon fiber-reinforced polymer (CFRP) holds considerable significance for their diverse applications. Here, an innovative and scalable strategy was developed to enhance the interfacial adhesion of Ti/CFRP hybrid laminates, which was achieved by introducing customized woven metallic fabrics to construct a heterogeneous interface through a simple and cost-effective spot welding method. Interestingly, it was found that the interlaminar mechanical performance and failure mode transition from snap-down instability to progressive softening behavior could be precisely tuned by adjusting the distribution configurations of the welded spots. The results demonstrated substantial improvements in interlaminar fracture energies with the implementation of customized intercalation. Specifically, mode I initiation and propagation were enhanced by approximately 276% and 144%, respectively, while mode II initiation improved by approximately 242%. These improvements were attributed to the activation of new dissipative mechanisms, including interfacial topological texture interlocking, adhesive failure, multiphase bridging (involving woven metallic fabric, welded spots and carbon fiber), as well as cross-layer migration of the interlaminar cracks. The use of customized intercalation thus proves to be a promising strategy for constructing heterogeneous interface and offers valuable insights into the interlaminar design for hybrid structures.

3D-printed titanium scaffolds loaded with gelatin hydrogel containing strontium-doped silver nanoparticles promote osteoblast differentiation and antibacterial activity for bone tissue engineering.

Bone tissue engineering offers a promising alternative to stimulate the regeneration of damaged tissue, overcoming the limitations of conventional autografts and allografts. Recently, titanium alloy (Ti) implants have garnered significant attention for treating critical-sized bone defects, especially with the advancement of 3D printing technology. Although Ti alloys have impressive versatility, their lack of cellular adhesion, osteogenic and antibacterial properties are significant factors that contribute to their failure. Hence, to overcome these obstacles, this study aimed to incorporate osteoinductive and antibacterial cue-loaded hydrogels into 3D-printed Ti (3D-Ti) scaffolds. 3D-Ti scaffolds were synthesized using the direct metal laser sintering method and loaded with a gelatin (Gel) hydrogel containing strontium-doped silver nanoparticles (Sr-Ag NPs). Compared with Ag NPs, Sr-doped Ag NPs increased the expression of Runx2 mRNA, which is a key bone transcription factor. We subjected the bioactive 3D-hybrid scaffolds (3D-Ti/Gel/Sr-Ag NPs) to physicochemical and material characterization, followed by cytocompatibility and osteogenic evaluation. The microporous and macroporous topographies of the scaffolds with Sr-Ag NPs showed increased Runx2 expression and matrix mineralization, with potent antibacterial properties. Therefore, the 3D-Ti scaffolds incorporated with Sr-Ag NP-loaded Gel hydrogels favored osteoblast differentiation and antibacterial activity, indicating their potential for orthopedic applications.

Electrically-assisted tension and cover forming of high-temperature Ti-55 titanium alloy

Electrically-assisted tension and cover forming of high-temperature Ti-55 titanium alloy

Enhancing surface chemistry and wetting behavior of laser-modified Ti–6Al–4V surgical titanium alloy surfaces through wet deposition of biogenic hydroxyapatite

This study focuses on enhancing the surface properties of surgical titanium alloys (Ti–6Al–4V) to optimize their suitability for biomedical implant applications. Direct laser writing (DLW) was used to modify the titanium surface and facilitate the deposition of biohydroxyapatite (BHA) particles through wet deposition and the coalescence phenomenon. Four types of etching patterns were tested, resulting in biomimetic bone-like surfaces with microtextured features, exhibiting suitable hydrophilic characteristics for biomedical implants. The resulting surfaces were characterized structurally, morphologically, chemically, and in terms of wettability. X-ray diffraction was performed to validate the titanium alloy composition and determine the crystallite size of BHA particles, both before and after thermal treatment. Optical and electron microscopy results demonstrated that the etching pattern density directly impacts the distribution and anchoring of BHA particles, with denser patterns leading to better particle fixation. Dense etching patterns were found to reduce the wettability of Ti surfaces. However, after coating with BHA particles, the contact angle decreased, resulting in more wettable surfaces. Energy-dispersive X-ray spectroscopy (EDS) mapping revealed variations in elemental distribution across different samples, providing an elemental composition analysis that supports the findings from optical and electron microscopy. The effectiveness of BHA deposition is closely tied to the density and pattern of the surface texturization. Overall, this study presents a straightforward yet effective methodology to optimize the surface properties of titanium alloys, potentially enhancing their compatibility with biological tissues.

Effect of the APS YAG coating on the fretting wear properties of Ti60 titanium alloy

To enhance the fretting wear resistance of Ti60 titanium alloy, a YAG coating was applied to the surface using the APS (atmospheric plasma spray) process, followed by an investigation of its fretting wear performance. Nanoindentation technology was employed to evaluate nanomechanical properties, and subsequently, techniques including SEM, EDS, TEM, XRD, XPS, and laser confocal microscopy were utilized to characterize microstructural features of the wear marks and the composition of wear debris. The results indicated that, owing to the presence of the APS YAG coating, the surface nanohardness of the Ti60 titanium alloy increased from 4.4 GPa to 11.06 GPa, while the fretting friction coefficient decreased from 0.186 to 0.155, and the volume wear is reduced by 80.53 %, which significantly improves the fretting wear resistance of Ti60 titanium alloy. As the number of fretting cycles increased, a complete friction layer formed on the surface of the Ti60 titanium alloy, leading to a decrease in fretting friction coefficient and a shift in the wear mechanism. Ultimately, a mixed mechanism was observed involving oxidative wear, abrasive wear, fatigue-induced peeling of the friction layer, and localized plastic deformation. Conversely, the fretting wear mechanism of the APS YAG coating consistently demonstrated abrasive wear, adhesive wear, and fatigue-induced cracking and spalling of the coating.

Fracture mechanism of Ti60 alloy at high temperature in very high cycle fatigue regime and fatigue life prediction

AbstractThis study aimed to investigate the failure mechanism of Ti60 titanium alloy in the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) at 500°C. Ti60 specimens were characterized before and after the 500°C VHCF test, and the fracture surfaces were observed. The results show that there are three different fatigue failure mechanisms at 500°C: (i) equiaxed primary α phase (αp) cleavage, forming small unsmooth facets and rough fracture area (RA), and fusion of non‐adjacent facets to grow into the main crack. (ii) αp grains gather into large grain with triple junction, and large grain slip to form large fusion facet. (iii) Oxide shedding and then cracks form. A dynamic recurrent neural network model is used to predict the fatigue life of Ti60 alloy, 91% of the overall predictions were within the scatter band of 3.0, and 100% were within the scatter band of 5.0.

Study of titanium alloy Ti–Al–Zr–Nb–V during heating under deformation and its phase transformation features

An alloy based on Ti–Al–Zr–Nb–V was prepared and its deformation behavior at elevated temperatures was studied. The microstructure and phase of the alloys were characterized by optical microscopy, scanning electron microscopy, thermal analysis, and mechanical testing. The results showed that the Ti–Al–Zr–Nb–V alloy, when stretched, exhibits a superplasticity effect in the range of 975℃ to 1100℃, with an elongation of up to 400%. It was found that superplasticity develops in the temperature region of the α+β→β transition and is accompanied by a change in grain size and redistribution of alloying elements among phases.

Biomechanical comparison of polyetheretherketone rods and titanium alloy rods in transforaminal lumbar interbody fusion: a finite element analysis

BackgroundWhether polyetheretherketone (PEEK) rods have potential as an alternative to titanium alloy (Ti) rods in transforaminal lumbar interbody fusion (TLIF) remains unclear, especially in cases with insufficient anterior support due to the absence of a cage. The purpose of this study was to investigate biomechanical differences between PEEK rods and Ti rods in TLIF with and without a cage.MethodsAn intact L1-L5 lumbar finite element model was constructed and validated. Accordingly, four TLIF models were developed: (1) Ti rods with a cage; (2) PEEK rods with a cage; (3) Ti rods without a cage; and (4) PEEK rods without a cage. The biomechanical properties were then compared among the four TLIF constructs.ResultsWith or without a cage, no obvious differences were found in the effect of PEEK rods and Ti rods on the range of motion, adjacent disc stress, and adjacent facet joint force. Compared to Ti rods, PEEK rods increase the average bone graft strain (270.8-6055.2 µE vs. 319.0-8751.6 µE). Moreover, PEEK rods reduced the stresses on the screw-rod system (23.1–96.0 MPa vs. 7.2–48.4 MPa) but increased the stresses on the cage (4.6–35.2 MPa vs. 5.6–40.9 MPa) and endplates (5.7–32.5 MPa vs. 6.6–37.6 MPa).ConclusionsRegardless of whether a cage was used for TLIF, PEEK rods theoretically have the potential to serve as an alternative to Ti rods because they may provide certain stability, increase the bone graft strain, and reduce the posterior instrumentation stress, which might promote bony fusion and decrease instrumentation failure.

Aging Treatment Induces the Preferential Crystallographic Orientation of αs in the Near-α Titanium Alloy Ti60

In this article, we subjected the Ti60 alloy to solid-solution treatment at 1020 °C and aging treatment at 600 °C, respectively, achieving a bimodal microstructure. The microstructures obtained after aging treatment showed no significant difference in the primary α-phase content, size, and width of the lamellar α phase. This suggests that the final microstructure morphology is primarily determined by the solid-solution temperature, with the aging process exerting less pronounced effects on microstructural alterations. Furthermore, we investigated the effect of solid-solution and aging treatment on the crystallographic orientation evolution of the secondary α phase (αs) in the near-α titanium alloy Ti60. The αs phase displays a random orientation in solid-solution treatment sample, while it demonstrated a preferential {0 1 −1 0} orientation after aging treatment. This interesting phenomenon is attributed to the enhanced variant selection resulting from the dissolution of variant near 60° and 90° during aging. Furthermore, the αs with {0 1 −1 0} orientation nucleated at the grain boundary and coalesced into larger αs lath with increasing aging time, further contributing to the αs {0 1 −1 0} texture.

Simulation and experimental research on longitudinal-torsional ultrasonic vibration drilling of CFRP/Ti laminates

Carbon fiber reinforced polymer (CFRP) and titanium alloy (Ti) laminated materials are extensively employed as primary load-bearing structures in aerospace engineering due to their exceptional characteristics. During the drilling process of CFRP/Ti laminates, issues like delamination and burr formation significantly impede the overall performance of these laminates. The finite element simulation was carried out to address above challenges using longitudinal-torsional ultrasonic vibration drilling (LT-UVD) of CFRP/Ti laminates. A three-dimensional solid model of CFRP/Ti laminates was developed using the ABAQUS custom VUMAT subroutine interface. A cohesive element was skillfully incorporated into the model to simulate delamination defects in the CFRP material effectively and to elucidate the material damage trends and stress distribution throughout the drilling process of laminated materials. The results obtained from the finite element simulation are meticulously compared with experimental data, revealing a consistent trend in the axial force curve. The simulated axial force’s peak value is 14.45% lower than the peak value obtained from experimental observations. The findings of this research substantiate the efficacy of the developed finite element model for LT-UVD of CFRP/Ti. The model successfully predicted the changing trend of axial force and layered defects during the drilling process. Moreover, it provides a visually intuitive instantaneous cutting state and stress distribution, imparting valuable insights into the intricate drilling mechanisms involved in CFRP/Ti laminates.

Microstructure and mechanical properties of Ti6Al4V/W bimetallic structure via selective laser melting

The titanium alloy Ti–6Al–4V (TC4) and tungsten (W) possess excellent complementary properties that would be useful for a wide range of industrial applications if they could be suitably combined. Selective laser melting was applied to prepare TC4/W specimens with a bimetallic structure. A strong bond without interfacial macrocracks was obtained by adjusting the laser line energy density to <0.75 J/mm. The bond interface of the bimetallic structure reached a microhardness of 503 ± 20 HV, which was harder than that of the two base materials, and the transverse and longitudinal ultimate compressive strengths were 1510 ± 40 MPa at strains of 20%–22.5%. Three-point bending experiments showed that when TC4 was used as the base material, the flexural strength of the specimen was 2210.5 ± 44.5 MPa. The high strength of the bond interface was attributed to sufficient agitation of the molten pool and reinforcement by fine crystalline grains. The agitation was provided by the melting and elemental diffusion of TC4 owing to the high energy input during the formation of W, and the fine crystalline grains were obtained by the dispersed W particles providing multiple nucleation sites for liquid TC4. The bimetallic structure retained the strength of W and toughness of TC4, which bodes well for its industrial application.

Numerical study on the heat effect on the drilling damage of Ti/CFRP stacks

AbstractCarbon fiber reinforced plastics (CFRP) has strong sensitivity to temperature, as the stacking sequence is titanium alloy (Ti) to CFRP, the damage of CFRP is more severe due to the accumulation of cutting heat. In this study, a stress‐strain constitutive model of CFRP with the effect of thermal stress is proposed. On the basis, a simulation model of drilling Ti/CFRP stacks is established to explore the heat effect on the drilling damage. Based on the results, it can be concluded that the burr of Ti at hole exit is generally low due to the support of CFRP, and the burr height increases by 56.61% as the temperature rises from 182.02 to 355.69 °C. Besides, the intralaminar damage of CFRP is mainly caused by the fiber tensile failure and matrix tensile failure, and the matrix tensile failure is more affected by temperature. Moreover, delamination of CFRP decreases slightly with the reduce of drilling temperature. In addition, serious damage of CFRP on the hole wall usually occurs within the cutting angle of 90° to 135°, and pit defects can be reduced in a lower drilling temperature.Highlights A thermal effect stress‐strain constitutive model of CFRP is proposed. Ti/CFRP drilling model is developed based on the proposed constitutive model. Fiber and matrix tensile failure are main form of intralaminar damage of CFRP. Matrix tensile failure is more sensitive to temperature.

Multiaxial fatigue life prediction based on effective factor with shear/axial stress ratio for Ti60 titanium alloy in very high cycle regime

Fatigue failure mechanism of Ti60 titanium alloy under tension–torsion multiaxial loading in the very high cycle regime was studied first, and the results showed that the shear/axial stress ratio directly affects the failure mechanism. When the shear/axial stress ratio is relatively small, cracks tend to originate from the subsurface in single-point initiation mode, and the larger the shear/axial stress ratio, the more cracks tend to originate from the surface in multi-point initiation mode. Then, a pragmatic equivalent method for multiaxial to uniaxial load based on the law of shear/axial stress ratio on fatigue strength was proposed. Based on this method and uniaxial S-N curve, the fatigue lives of Ti60 specimens under shear/axial stress ratios of 1.37, 1.95, and 3.53 was predicted, and the experimental results showed that the prediction error is basically within a factor of 3.