Pure Ti Foil Research Articles

In-situ study of tensile behavior of Ti/Al laminated metal composites fabricated via ultrasonic additive manufacturing

In this paper, the in-situ tensile behavior of Ti/Al laminated metal composites (LMCs) prepared via ultrasonic additive manufacturing (UAM) was investigated by optical microscopy combined with digital image correlation. Compared with pure Ti foil and Al/Al LMCs processed via UAM, the Ti/Al LMCs exhibit a significantly larger plasticity with intermediate tensile strength. This can be attributed to (ⅰ) strain dispersion in Ti/Al LMCs, (ⅱ) necking inhibiting due to well-bonded interface during early stage of deformation, and (ⅲ) microcracking during late stage of deformation at the rough Ti/Al interfaces, which originate from direct contact between Ti foil and sonotrode.

Joining of C/C composite with high entropy alloy interlayers via spark plasma sintering and its mechanical strength at 1600 ℃

A novel method is developed to join C/C composites via spark plasma sintering (SPS) using ZrHfNbTa and TiZrHfTa high entropy alloys as interlayers. The joint microstructure, interface reaction and shear strength at 1600 ℃ were investigated. For both interlayers, the C/C joint consisted of a single high entropy carbide phase. However, the use of different high entropy alloy interlayers resulted in differences in the micro-homogeneity of the formed high entropy carbide as well as the thickness of the joint zone. Both formed (Zr-Hf-Nb-Ta)C and (Ti-Zr-Hf-Ta)C high entropy carbides, which were homogeneous on the atomic scale, and no impurities were found at the grain boundaries. The shear strengths of the C/C-ZrHfNbTa-C/C joint and C/C-TiZrHfTa-C/C joint at 1600 ℃ were comparable, with values of 23.5 ± 1.2 MPa and 24.6 ± 2.5 MPa, respectively, which are more than twice the shear strength obtained with pure Ti foil (11.6 ± 3.6 MPa).

Phase transition induced low temperature diffusion bonding of Zr-4 alloy using a pure Ti interlayer

In this paper, a low-temperature sealing of Zr-4 alloy induced by α→β phase transitions by using a pure Ti interlayer was reported. Both Ti and Zr compositions show smooth transition at the Ti/Zr interface when no phase transition happened. While a Ti, Zr elemental distribution plateau, corresponding to a light gray diffusion zone, was found at the Ti/Zr interface after a β-(Ti, Zr) phase transition happened. Results show that, to achieve the same shear strength of 294 MPa, the bonding temperature was reduced by 100 ℃ after using the pure Ti foil interlayer. Molecular dynamics (MD) simulation data show that the diffusion coefficients of Zr in β-(Ti, Zr) and α-(Ti, Zr) are 0.194 × 10−11 m2/s and 0.015 × 10−11 m2/s respectively, which further proves the β-(Ti, Zr) phase transition zone can indeed facilitate the diffusion of Zr-4/Zr-4 couples and lower the diffusion bonding temperature.

Two kinds of α/β phase transformations and enhanced strengths of the bonded interface in laminated Ti alloys

Metastable β Ti alloys are becoming increasingly competitive in the aircraft industry, while the study on diffusion bonding of this type of Ti alloy has been rarely reported up to now. Diffusion bonding of TC4/TB5 alloys with and without pure Ti foil interlayer was carried out to fabricate laminates and analyze the microstructural evolution and mechanical properties. This study reports the first-hand finding on β grains characterized by dendritic morphology at the TC4/Ti/TB5 interface, which results from retained phase due to the asynchronous precipitation and growth of α grains instead of β grains growth. In addition, there are two kinds of α precipitates from β matrix complying with the Burgers orientation relationship at the bonded interface, which is related to the two kinds of α→β phase transformations during heating. The bonded interfaces with fine α and β laths give rise to positive function to the hardness and tensile strengths of the laminated TC4/TB5 alloys.

Formability improvement of hot-pressed Ti/Al laminated sheet by TiAl3 layer growth and crack healing during deformation

Ti/Al laminated sheets were prepared by hot pressing pure Ti and Al foils at 630 °C/20 MPa for different times. The thickness of TiAl3 layers increased, and the elongation of the Ti/Al laminated sheet decreased with the hot-pressing time, where the 15 min-hot-pressed sheets showed the most extensive elongation (135% at 600 °C). The crack initiation and propagation behavior of the 15 min-hot-pressed sheets were investigated by the tensile test with different strains. When the testing temperature was between room temperature (RT) and 400 °C, the cracks in TiAl3 layers were parallel to each other and perpendicular to the tensile direction. The size and amounts of cracks increased with the strain. At 600 °C, the parallel cracks appeared after 70% deformation, while at 100% strain, the TiAl3 layer thickness increased significantly, accompanied by many disordered and discontinuous cracks. The 15 mins-hot-pressed sheet shows excellent gas bulging formability, where the height to radius ratio reached 0.9. The improved sheet formability is because the cracks were filled and healed by the newly formed TiAl3 phase during deformation at 600 °C. The TiAl3 layer, therefore, was maintained for a longer time before rupturing, which greatly improved the coordination deformation ability of various layers.

Grain size effect of pure Ti foils by micro blanking-deep-drawing compound process

Grain size effect of pure Ti foils by micro blanking-deep-drawing compound process

Evaluation of heat removal performance of a sealed Li target for an accelerator-driven neutron source of Boron Neutron Capture Therapy at Nagoya University

An accelerator-driven neutron source has been developed in Nagoya University for boron neutron capture therapy using a new concept of thick lithium (Li) target in which protons are stopped in a Li layer. A sealed Li target developed consists of a Li sheet placed on a copper (Cu) base plate equipped with water-cooled channels and a titanium (Ti) foil seal to cover Li surface. The proton beam injected into the target is produced through the proton–Dynamitron accelerator (IBA) with a maximum energy of 2.8 MeV and a current of 15 mA. The results of our previous study confirmed that the target was not damaged when irradiated with an acceleration energy of 1.8 MeV and a current of 0.5 mA (heat input of 4.6 MW/m2). To keep the soundness of the target up to 6–7 MW/m2, it is considered to be essential to improve the bonding between the Ti foil and Li interface, which will contribute the heat removal. It was suggested from our previous experiences that the bonding property may be improved by forming a Cu–Li alloy at the Ti–Li interface. In this paper, we evaluate the heat removal performance of a sealed Li target with Cu–Li alloy formation to improve the target durability. The sealed Li target was produced using a “Cu-coated pure Ti foil”, in which Cu was deposited on the surface of a Ti foil with a thickness of 0.2μm. The use of Cu-coated pure Ti foil actively forms Cu–Li alloys at the Ti–Li interface. For comparison, sealed Li targets were produced with pure Ti foil, and irradiation tests were conducted on each target. The heat removal performance was evaluated by electron beam irradiation using the active cooling teststand 2 (ACT2), a high heat flux test facility, and proton beam irradiation using the Dynamitron accelerator. We obtain a result that the Cu-coated pure Ti foil-sealed Li target has a heat removal capacity of 11 MW/m2, about five times higher than that of the pure Ti foil-sealed Li target. This confirmed that the Cu–Li alloy contributed to the improvement of the heat removal performance. For the proton beam irradiation test, a Cu-coated pure Ti foil target was produced and irradiated for 26 h at an acceleration energy of 1.8 MeV and an average current of 3.5 mA, where no neutrons were generated. The tests confirmed that the Cu-coated pure Ti foil target could withstand 26 h of irradiation at a heat input of 9.0 MW/m2. About anticipated degradation of the heat removal performance due to stopping the protons in the Li layer, no change was observed during this long irradiation test, in which 2.15 × 1024 protons were injected into the Li layer. Although further long-time irradiation test will be needed in the future, at present we have confirmed that there is no problem with stopping protons in the Li layer.

Nanostructured anatase TiO2 as anode of high‐performance lithium‐ion batteries

AbstractNanostructured anatase TiO2 (NSA‐TiO2) was synthesized via electrochemical anodization of pure Ti foils in a fluorine‐containing electrolyte. The synergistic effects of the anodization period (1 and 2 h) and the surface condition of Ti foils (scratched and unscratched) before anodization was investigated. Four nanostructure variants—unscratched 1 h, unscratched 2 h, scratched 1 h, and scratched 2 h with average pore diameters 15 ± 7.4, 10.1 ± 8.5, 7 ± 7.12, and 8.1 ± 3.79 nm, respectively, were fabricated to assess as negative electrodes of high‐performance lithium‐ion batteries (LIBs). The corresponding first cycle discharge capacities of as‐synthesized NSA‐TiO2 exhibited 433, 93.33, 453.33, and 460.0 mAhg−1. LIB with scratched 1 h NSA‐TiO2 as anode exhibited very propitious outcomes. The reversible capacity at a high 1 C current rate was displayed as 100 mAhg−1 even after 400 cycles along with 103.27% coulombic efficiency. The superior electrochemical performances are attributed to its high specific surface area due to its nanoporous structure. These nanoporous structures provide higher contact between electrodes and electrolytes, shortening the diffusion pathways for conductive ions and electrons that ensured faster kinetics. However, scratching operations increased surface area in the final nanostructure while the short anodization period substantially increased the number of pores.

Superior strength–ductility synergy of (TiC + Ti5Si3)/Ti composites with nacre-inspired architecture

Inspired by the ultrastrong and tough nacre structure, in this study, we prepared in-situ titanium (Ti) matrix composites (TMCs) containing laminated Ti, planarly aligned TiC and vertically distributed Ti5Si3 phases, which is close to the unique “brick-and-mortar” architecture of nacre. This concept was realized via electrophoretic depositing Si powders and graphene oxides (GOs) on pure Ti foils followed by spark plasma sintering. Results showed that dramatically higher yield strength (YS) of 829 MPa could be achieved in the composite, which is 178% higher than that of pure Ti counterpart while maintaining good plasticity of 8.1% in elongation. Compared with the laminated TiC/Ti composite with higher strength and moderate plasticity, simultaneous improvement in strength (19%) and ductility (33%) was attained in the nacre-like composites, leading to superior strength–ductility synergy. The strengthening and toughening mechanism were discussed based on microstructures and fractographs. Our study offers a facile approach to fabricating large-sized nacre-like artificial composites with outstanding properties.

Microstructure and mechanical properties of in situ TiC/Ti composites with a laminated structure synthesized by spark plasma sintering

A series of novel in situ TiC/Ti composites with laminated microstructure have been fabricated via electrophoretic deposition followed by spark plasma sintering (SPS), in which the electrophoretic deposition has been used to deposit graphene oxides (GOs) on commercially pure Ti foils and the SPS has been used to induce in situ reaction between Ti and GOs to form TiC and simultaneously achieve densification. With increasing deposition duration, the volume fraction of TiC reinforcement increases and the grain size of Ti matrix decreases in the as-sintered composites, resulting in continuous strength increment. Attributed to the introduction of TiC reinforcement and laminated structure, a strength increment of 93.9% can be reached with a considerable elongation of 6.1%. Moreover, different strengthening mechanisms are discussed and quantitatively evaluated based on microscopy analysis. • Laminated TiC/Ti composites were synthesized by spark plasma sintering. • The composites exhibited better strength-ductility combination. • The strengthening mechanisms are discussed and quantitatively evaluated.

Effects of SiC Fibers and Laminated Structure on Mechanical Properties of Ti-Al Laminated Composites.

Ti/Ti–Al and SiCf-reinforced Ti/Ti–Al laminated composites were fabricated through vacuum hot-pressure using pure Ti foils, pure Al foils and SiC fibers as raw materials. The effects of SiC fiber and a laminated structure on the properties of Ti–Al laminated composites were studied. A novel method of fiber weaving was implemented to arrange the SiC fibers, which can guarantee the equal spacing of the fibers without introducing other elements. Results showed that with a higher exerted pressure, a more compact structure with fewer Kirkendall holes can be obtained in SiCf-reinforced Ti/Ti–Al laminated composites. The tensile strength along the longitudinal direction of fibers was about 400 ± 10 MPa, which was 60% higher compared with the fabricated Ti/Ti–Al laminated composites with the same volume fraction (60%) of the Ti layer. An in situ tensile test was adopted to observe the deformation behavior and fracture mechanisms of the SiCf-reinforced Ti/Ti–Al laminated composites. Results showed that microcracks first occurred in the Ti–Al intermetallic layer.

Microstructure and superior mechanical property of in situ (TiBw + TiCp)/Ti composites with laminated structure

The strength and ductility of titanium matrix composites (TMCs) hardly co-exist and show a trade-off between each other. In order to balance the strength and ductility of TMCs, in situ TiB whiskers (TiBw) and TiC particles (TiCp) strengthened Ti composites with laminated structure were constructed via electrophoretic depositing (EPD) boron (B) powders + graphene oxides (GOs) on pure Ti foils followed by spark plasma sintering (SPS). The experiment results reveal that increasing EPD duration leads to more synthesized TiBw + TiCp reinforcements accompanied by decreased grain size of Ti matrix in the sintered composites, which favorably results in gradually enhanced strength. A maximum yield strength (YS) of 569 MPa is achieved in the laminated composite, which is 75.6% higher than that of pure Ti sample (YS: 324 MPa). Meanwhile, the composite still owns a relatively higher elongation of 12.0%. The achievement of good ductility should benefit from the laminated architecture which exerts constraint effect on crack propagation. This work provides a short cut to achieve strength-ductility synergy in TMCs.

Enhancement of uniform plastic deformation for pure titanium foils by applying pre-strain combining with resistance heating method for microforming

Pure titanium (Ti) is usually deformed at elevated temperatures due to its poor formability at room temperature (RT), resulting in its strength reduction after deformation. Applying pre-strain combining with resistance heating (RH) method, which can be conducted at one procedure, was proposed to enhance its plasticity in this work. The influence of the proposed process on tensile deformation of pure Ti foils with 50μm thick was investigated using a RH assisted tensile testing system. Full strain field was measured by a digital image correlation (DIC) system with laser speckles. Uniaxial tensile pre-strain ranging from 1% to 2% was applied at a low temperature of 160°C with relatively high nominal strain rates of 10−2 and 10−1s−1. Then tensile tests were conducted at RT with a nominal strain rate of 10−3s−1. As results, although the ultimate tensile strength (UTS) slightly decreased with increasing pre-strain, the maximum decreasing rate was within 4%, indicating that the effect of pre-strain on UTS is negligible. The strain distribution analyzed from DIC was relatively uniform at UTS. Uniform elongation increased with increasing pre-strain. The maximum increasing rate achieved 36%. It is confirmed that the heating rate using RH for heating Ti foils with 50μm thick is about 340 times larger than that for heating Ti sheets with 1mm thick. The quick response of RH makes it possible for the application of the proposed process to mass production for manufacturing microparts.

Spark Plasma Diffusion Bonding of TiAl/Ti2AlNb with Ti as Interlayer

To solve the problem of poor weldability between TiAl-based and Ti2AlNb-based alloys, spark plasma diffusion bonding was employed to join a TiAl alloy and a Ti2AlNb alloy with a pure Ti foil as interlayer at 950 °C/10 KN/60 min. After welding, slow cooling was carried out at a rate of 5 °C/min, followed by homogenization at 800 °C for 24 h. The microstructural evolution and elemental migration of the joint were analyzed via a scanning electron microscope equipped with an energy dispersive spectrometer, while the mechanical properties of the joint were assessed via microhardness and tensile tests. The results show that the spark plasma diffusion bonding formed a joint of TiAl/Ti/Ti2AlNb without microcracks or microvoids, while also effectively protecting the base metal. Before heat treatment, the maximum hardness value (401 HV) appeared at the Ti2AlNb/Ti interface, while the minimum hardness value (281 HV) occurred in the TiAl base metal. The tensile strength of the heat-treated joint at room temperature was measured to be up to 454 MPa, with a brittle fracture occurring in the interlayer. The tensile strength of the joint at 650 °C was measured to be up to 538 MPa, with intergranular cracks occurring in the TiAl base metal.

Size Effect of Ultra Pure Ti Thin Strip under Asymmetrical Rolling

In order to study the size effect on properties of ultra pure Ti tensile tests were performed with ultra pure Ti foil (thickness range from 30μm to 280μm) by asymmetrical rolling. A pronounced size effect was observed at thickness of 34μm. The results were shown that the ultimate strength were increased as sample thickness down from 280μm to 34μm, however, were decreased as the thickness from 34μm to 30μm with ultrahigh strain. These features seemed to be link to the increasing of fraction of surface grain to volume, which led to the less districting on dislocation slip.

Strengthening and toughening mechanisms of titanium-nitrogen alloy with a laminated structure fabricated by spark plasma sintering

Laminated Ti–N alloy consisting of hard N-rich interfacial layers and soft Ti matrix layers has been fabricated successfully by spark plasma sintering (SPS) with stacking nitrided commercially pure (CP) Ti foils. It shows 100% higher tensile/bending strength and 25%~66% higher fracture toughness than the laminated Ti prepared by the same SPS processing with stacking CP Ti foils for comparison. Multiple strengthening and toughening mechanisms have been found to take responsibility for the good performance of the laminated Ti–N.

Structure and mechanical properties of Ni/Ti multilayered composites produced by accumulative roll-bonding process

This research studies the structure and mechanical properties of Ni/Ti multilayered composites produced from commercial pure Ni and Ti foils by accumulative roll-bonding technique. To investigate these properties, scanning electron microscopy, Vickers microhardness, and uniaxial tensile tests were conducted at different processing cycles. Studies showed that in terms of structure, Ni and Ti layers maintain their continuity even up to 10 cycles of accumulative roll-bonding. Moreover, the energy-dispersive spectroscopy in scanning electron microscopy detected no deformation induced diffusion or reactive interfacial zones. It was found that by increasing the accumulative roll-bonding cycles, tensile and yield strengths as well as the hardness of the composite enhance and the total elongation reduces continuously.

Effect of DI Water Content on the Growth of Anatase TiO<sub>2</sub> Nanotubes Synthesized by Anodization Process

Vertically aligned anatase TiO2 nanotubes (NTs) were fabricated by anodization of a pureTi foil in ethylene glycol solutions containing different concentrations of deionized (DI) water. Themorphology, elemental composition, and crystallization of TiO2 nanostructures were analyzed byfield emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Ramanspectroscopy, and X-ray spectroscopy (XPS), respectively. The diameter and length of TiO2 NTswere controlled by varying concentrations of DI water. Furthermore, we found that TiO2 NTs in DIwater 12 wt. % was suitable for further applications in UV photodetector due to it has a high volumeto surface area ratio and long tube. TiO2 NTs have a high potential in various applications such as UVphotodetectors, gas sensor, dye sensitized solar cells, and photocatalysts.

TEM study of microstructural characteristic and evaluation of mechanical performance for the hastelloy N/Ti/Hastelloy N superalloy joint brazed for diverse soaking time

The purpose of this work was to describe and discuss the fundamental issues involved in brazing of Hastelloy N to Hastelloy N superalloy using pure Ti foil at 1333 K for different soaking time (1∼90 min). A detailed electron microscopy examination (transmission electron microscopy and high-resolution transmission electron microscopy) was performed to study the microstructure of the joint. The mechanical performance of the joint was evaluated by a shear test. Results show that the brazed joint obtained could be described as Hastelloy N/Zone 1/Zone 2/Zone 1/Hastelloy N. The Zone 1 whose constitution was hardly affected through modifying the soaking time was produced because of the eutectic melting of Cr9Mo21Ni20 and Ni3Ti intermetallics. The constitution of Zone 2, however, was very sensitive to the joining condition. Among the soaking time under investigation, the highest joint average shear strength obtained was 350.4 MPa. The strength of the joint, as revealed, was closely related with the microstructure in the Zone 2. When the Hastelloy N superalloy was brazed for different soaking time, the microstructural evolution in the joint was clarified and its relationship with mechanical performance was built. The work will contribute to understand the brazeability of the Hastelloy series alloys and then broaden their applications.

Tension-tension fatigue behaviours of notched freestanding pure Ti foils with different thicknesses

This work addresses the mode I fatigue crack propagation behaviours of pure Ti foils using freestanding notched rectangular specimens under tension-tension cyclic loading. Compared to the 50-μm-thick foil, the 30-μm-thick foil exhibited a higher yield strength (σy) but a lower fracture toughness (KQ) and fatigue life (Nf) for the same loading conditions. The Paris constant m decreased from 5.12 to 4.45, when the foil thickness increased from 30 μm to 50 μm. The incomplete self-similarity parameter Z at the crack tip was found to be higher in the 30-μm-thick foils, resulting in a higher Paris constant m than that in the 50-μm-thick foils.