Cu-Ti Alloys Research Articles

Synthesis and Characterization of Self-Organized Oxide Layer Grown on Ti-Cu Alloys System for CO2 Reduction

Ti-Cu alloys could be used as a substrate to produce photoelectrode pn-heterojunctions to increase copper stability and consequently to improve photoconversion of CO2. Cu–Ti–O films were grown by anodizing directly of Ti–x%at.Cu (x= 0.5, 5.5, 10 and 50) and after these alloys were submitted different kinds heat treatment (annealing or quenching) to compare a directly influence of presents phases in nanotubes alloy substrate after it preparation by voltaic arc melting following a annealed or rapid quenching as heat treatment. All films presented TiO2 and copper dioxides in its compositions. These electrodes showed higher absorbance in visible light, anodic current for less copper alloy cathodic current equiatomic composition and copper stability for all cases due cu atomic insertion inside TiO2 crystal lattice and sharing oxygen atomic. The cathodic current varied in function of Cu concentration in the alloy.

Improved Corrosion Resistance of Selective Laser Melted Ti–5Cu Alloy Using Atomized Ti–5Cu Powder

The different types of metal powder used for selective laser melting (SLM) process would cause distinct corrosion behavior due to the uniformity of the obtained microstructure. The SLM-produced Ti–5Cu alloy using atomized Ti–5Cu metal powder (SLMed Ti–5Cu) in this work reveals a relatively uniform microstructure with overwhelming acicular α/α′ phase and shows great advantages on corrosion resistance compared with the SLM-produced Ti–5Cu alloy using the mixture powder (SLMed-M Ti–5Cu). The effect of the micro-galvanic cells decreases due to the undetectable Ti2Cu phase in the microstructure of the SLMed Ti–5Cu. An apparent passivation behavior was observed for SLMed Ti–5Cu instead of severe pitting phenomenon for the SLMed-M Ti–5Cu. The charge transfer resistance of SLMed Ti–5Cu in this work is 10.09 ± 2.63 MΩ cm2, which is significantly higher than that of SLMed-M Ti–5Cu (4.76 MΩ cm2). The above result indicates the atomized Ti–5Cu powder plays an important role in the formation of the uniform microstructure of SLMed product, thereby enhancing its corrosion resistance in Hank’s solution at 37 °C.

Investigation of the interfacial reactions between Sn-3.0 wt%Ag-0.5 wt%Cu solder and Cu[sbnd]Ti alloy (C1990HP)

The interfacial reactions between Sn-3.0 wt%Ag-0.5 wt%Cu (SAC) solder and CuTi alloy (C1990HP) using the solid/liquid reaction couple technique reflowed at 240, 255, and 270 °C for 10 min to 20 h was first investigated. The results revealed that the Cu6Sn5 phase and the precipitated Ti2Sn3 and Ag3Sn phases with a small grain size were formed and no Cu3Sn phase was observed in the SAC/C1990HP couple when the reflowing time was longer than 30 min. In addition, the Ti2Sn3 phase was observed among the upper the Cu6Sn5 phase. Comparing the SAC/Cu reaction couple, the thicker intermetallic compound (IMC) layers were observed in the SAC/C1990HP reaction couple. It was also shown that the massive spalling of the Cu6Sn5 phase in the SAC/C1990HP reaction couple for the prolonged reflowing time. Meanwhile, the Sn-rich layer was observed between the upper and lower Cu6Sn5 phases. When the reaction temperatures and times were increased, the small grain of the Cu6Sn5 phase was merged and ripened each other, and then spread over to the SAC solder. The hexagonal prism-shaped Cu6Sn5 phase was found when the Cu6Sn5 layer detached at the SAC/C1990HP interface. The IMC growth mechanism was diffusion controlled.

Effect of high-rate annealing on microstructure, martensitic transformation and shape memory behavior of TiNiCu melt-spun ribbons

The amorphous rapidly quenched quasi-binary TiNi–TiCu alloys containing 30–38 at.% Cu were crystallized by isothermal annealing at 500 °C for 300 s and by exposing to short electric pulse with a duration of 10 ms to study the effect of the annealing rate on their properties. The results obtained showed that electropulse crystallization fundamentally changed the microstructure of the alloys due to almost completely hindering the formation of brittle Ti-Cu phases. This leads to a significant increase in the enthalpy of the martensitic transformation and a considerable shift of the transformation range towards higher temperatures. It was found that reducing the crystallization time dramatically increases the plasticity and shape memory effect of the alloys.

Thermal conductivity of Cu-Ti/diamond composites via spark plasma sintering

Copper matrix composites reinforced with 50 vol% diamond particles were prepared by spark plasma sintering. The diamond particles, Cu-Ti alloy powder and Cu power were mixed in different mass ratios and sintered at a temperature of 925 °C for 10 min in vacuum. Effects of Ti content on microstructure and thermal conductivity of the Cu-xTi/diamond composites were studied in the range of 0–1 wt%. With Ti content increasing, the thermal conductivity of the Cu-Ti/diamond composites increases first and then decreases. The highest thermal conductivity of 529 W/(m·K) was obtained in the Cu-0.2Ti/diamond composite owing to the improved interfacial bonding and lower interfacial thermal resistance. The diffuse mismatch model and Hasselman-Johnson model were used to calculate the theoretical thermal conductivity of the Cu-Ti/diamond composites. It is shown that moderate content of Ti addition is good for improving the thermal conductivity of Cu/diamond composites, which is consistent with experimental results.

Morphological evolution of transformation products and eutectoid transformation(s) in a hyper-eutectoid Ti-12 at% Cu alloy

Evidences of both sluggish eutectoid and active eutectoid (not suppressible under rapid cooling) transformations have been found for the first time in a single hyper-eutectoid Ti-Cu alloy. Both of these types of eutectoid reactions have been investigated in detail, at different length scales, by coupling scanning electron microscopy (SEM),transmission electron microscopy (TEM) and atom probe tomography (APT). The unique three phase crystallographic relationship between the parent β (bcc) and the two product phases, α (hcp) and Ti2Cu, has been established. The extent of partitioning of the solute (Cu) between the two product phases has been determined by APT and is rationalised in terms of thermodynamic considerations. Based on the observed lattice site correspondence and the extent of solute partitioning, a possible mechanism of active eutectoid transformation is proposed.

Preparation of multicomponent thin films by magnetron co-sputtering method: The Cu-Ti case study

The paper discusses the preparation of multicomponent thin films of Cu-Ti composite with desired elemental composition using the pulsed magnetron co-sputtering technology. The technological goal described in the paper was deposition the Cu-Ti composite with elemental ratio of about 50/50 at%, which is close to the eutectic point from the Cu-Ti alloy system. A large difference in the sputtering yield (about seven-fold) of Cu and Ti metals was challenging, because of the features of used power supplies. Desired concentrations of the Ti and Cu elements were obtained as a result of application of multimagnetron sputtering system, where magnetrons were equipped with the Ti or Cu targets. Additionally, pulse power supply was used together with the pulse width modulation controller. Moreover, the article presents investigations of structural and mechanical properties of deposited Cu, Ti and Cu-Ti films with elemental composition of ca. 50/50 at.%. It was found that the two component Cu0.5Ti0.5 thin films were composed of Cu4Ti3 nanocrystallites built-in an amorphous matrix. As compared to the pure Cu and Ti thin films, the prepared composite exhibited improved hardness and better elasticity reflected in lower values of the Young's modulus. The results of nanoindentation investigations showed that the Cu0.5Ti0.5 composite thin film was characterized by the hardness of 7.59 GPa.

Influence Mechanism of Cu on High Temperature Oxidation Behavior of Titanium Alloys

The oxidation behavior and mechanism of Ti-Cu alloys (0≤w(Cu)≤20%) in the temperature range of 1000°C～1300°C are studied by thermogravimetric analysis(TGA) combined with SEM, EDS and XRD analysis methods. The results show that the oxidation rates of Ti-Cu alloys increase sharply when the temperature rises above 1000°C. The oxidation products have a three-layer structure, from the outside to the inside, which are dense outer oxide layer of TiO2, porous inner oxide layer of low valence oxide of Ti and Cu-enriched layer. With the increase of the temperature, the thicknesses of oxide layers of Ti-Cu alloy increase and the Cu-enriched phase increases gradually and melts. The melting Cu-enriched phase flows to the oxidation surface along the grain boundaries of the oxide layer. The high temperature oxidation resistance of Ti-Cu alloys declines with the increase of Cu content. The main reason is that more liquid Cu-enriched phase is formed and flows to the oxidation surface along the oxide grain boundaries in the Ti-Cu alloy, and Ti and O ions can diffuse more easily along the liquid Cu-enriched phase, which increases the oxidation rates.

Effect of Composition on the Strength and Electrical Conductivity of Cu-Ti Binary Alloy Wires Fabricated by Aging and Intense Drawing

The strength and electrical conductivity of Cu-Ti alloy wires fabricated by over-aging and intense drawing were investigated as a function of Ti content (2.7 to 4.3 at. pct). The microstructure of all over-aged Cu-Ti alloys before drawing showed mainly coarse cellular components laminating the plates of a terminal Cu solid solution and a β-Cu4Ti intermetallic compound precipitated discontinuously by grain boundary reactions. The volume fraction of β-Cu4Ti plates increased with Ti content, although the compositions of the two phases remained unchanged. When the over-aged alloys were drawn to the same deformation strain, the hardness and tensile strength of the wires increased monotonically with Ti content due to strain-induced strengthening; a high volume fraction of hard β-Cu4Ti fibers formed from laminating plates during drawing promoted a high dislocation density in the matrix. The electrical conductivity of the wires decreased gradually with Ti content due to the higher volume fraction of β-Cu4Ti fibers and due decomposition of the fibers during drawing. The overall performance of the Cu-Ti alloy wires improved as the Ti content increased and was superior to that of conventional Cu-Ti alloy wires fabricated by peak-aging and drawing, and to that of commercial Cu-Be alloy wires.

Antibacterial investigation of titanium-copper alloys using luminescent Staphylococcus epidermidis in a direct contact test

Commercially pure titanium (CP-Ti), used as oral implants, is often populated by various bacterial colonies in the oral cavity. These bacteria can cause Peri-implantitis, leading to loss of bone tissue and failure of implants. With the increased awareness of antibiotic resistance, research has been directed towards alternative solutions and recent findings have indicated titanium‑copper (Ti-Cu) alloys as a promising antibacterial material. The aim of this study was to produce homogeneous Ti-Cu alloys, with various concentrations of copper, and to characterise their antibacterial properties through direct contact tests, using luminescent bacteria, in addition to traditional materials characterisation techniques.Samples of CP-Ti and four different Ti-Cu alloys (1, 2.5, 3 and 10 wt%Cu) were produced in an arc-furnace, heated treated and rapidly quenched.X-ray diffraction revealed that Ti2Cu, was present only in the 10 wt%Cu alloy, however, scanning electron microscopy (SEM) indicated precipitates at the grain boundaries of the 3 wt%Cu alloy, which were confirmed to be of a copper rich phase by energy dispersive x-ray spectroscopy (EDS) analysis. EDS line scans confirmed that the alloys were homogenous. After 6 h, a trend between copper content and antibacterial rate could be observed, with the 10 wt%Cu alloy having the highest rate. SEM confirmed fewer bacteria on the 3 wt%Cu and especially the 10 wt%Cu samples.Although the 10 wt%Cu alloy gave the best antibacterial results, it is desired that the Cu concentration is below ~3 wt%Cu to maintain similar mechanical and corrosive performance as CP-Ti. Therefore, it is proposed that future work focuses on the 3 wt%Cu alloy.

Thermo-mechanical strengthening mechanisms in a stable nanocrystalline binary alloy – A combined experimental and modeling study

An immiscible nanocrystalline (NC) copper-tantalum (Cu-Ta) alloy is shown to exhibit a stable microstructure under thermo-mechanical loading conditions with exceptional mechanical strength (i.e., 1200 MPa strength at 298 K) indicating anomalous deformation mechanisms as compared to microstructurally unstable nanocrystalline materials. Therefore, in this work, various aspects of strength partitioning in such NC Cu-Ta alloys are discussed and the role of tantalum nanoclusters on the dominant deformation mechanism is presented as a function of temperature. Toward this, initially, the mechanical responses of NC Cu-Ta alloy were measured under uniaxial compression experiments at various temperatures. Later, atomistic simulations were performed along with the high-resolution electron microscopy to identify and validate the rate limiting mechanism behind the plastic deformation in NC Cu-Ta alloys. In general, the observed trend through experiments and simulations identify a transition from a dislocation – nanocluster interaction mediated deformation mechanism to one controlled by grain boundary strengthening as the temperature increases. The former mechanism is shown here to have a crucial role in the observed strengthening behavior of microstructurally stable NC materials. Overall, the paper demonstrates that through effective nano-engineering techniques, it is expected to extend the scope of nanocrystalline materials to a number of engineering design applications.

Effect of multiaxial cryoforging on microstructure and mechanical properties of a Cu-Ti Alloy

Cu-Ti alloy, processed by multiaxial forging (MAF) at cryogenic temperature with a cumulative strain up to 1.64, was investigated for microstructure and mechanical properties. The deformed microstructures were analyzed using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The average grain size of 2 μm was achieved in the deformed sample after 3 cycles of MAF. TEM studies indicated that the shear bands width of the deformed sample after 3 cycles reduced to 1 μm. Tests for mechanical properties indicated an increase in tensile strength and hardness and it was found to be correlated with an increase in dislocation density and grain boundary strengthening mechanism. Ultimate tensile strength (UTS) of 390 MPa, 480 MPa, and 590 MPa was observed in MAF processed samples after 1, 2, and 3 cycles, respectively. Hardness increased from 65 Hv (as-received) to 240 Hv after 3 cycles of MAF. Fractography analysis showed that, with an increase in number of MAF cycles, dimple size reduced up to 1 cycle and percentage elongation increased after 2 cycles of MAF.

Effects of Trace Alloying Elements Fe and Cr on the Microstructure and Aging Properties of Cu-3Ti Alloy Foils

In this work, the effects of an addition of trace alloying elements, Fe and Cr, on the mechanical and electrical properties and corrosion resistance of Cu-3Ti alloy foils, have been investigated. The results showed that the individual addition of Fe leads to the formation of Fe2Ti intermetallic phase, which refines the grain size, in the solution-treated condition. With a combined addition of Fe and Cr, the formation of the (FeCr)2Ti phase and the precipitation of the β′-Cu4Ti phase resulted in increased hardness in the peak-aged condition. The ultimate tensile strength and yield strength of the peak-aged Cu-Ti-Fe-Cr alloy were 13% and 5.7% higher, than those of the Cu-3Ti alloy, respectively. The electrical conductivity of the peak-aged Cu-Ti-Fe-Cr alloy was 3.3% higher than that of the Cu-Ti-Fe alloy, due to the finer (FeCr)2Ti phase and the less residual Ti atoms, in the Cu matrix. The combined addition of Fe and Cr elements could improve the corrosion resistance of the Cu-Ti alloy. The Cu-Ti-Fe-Cr alloy foil could obtain the best integrated properties, and the hardness, ultimate tensile strength, and electrical conductivity were 357.1 HV, 1068 MPa and 12.5% IACS, respectively.

Microstructure, Mechanical Properties, and Sliding Wear Behavior of Spark Plasma Sintered Ti-Cu Alloys

Ti-Cu alloys have attracted significant interests for use in dental and orthopedic implants because of excellent antibacterial activity. However, limited research efforts have been devoted to their sliding wear behavior. Herein, we have fabricated nearly fully dense ultra-fine-grained Ti-Cu alloys with the Cu contents of 5 and 25 at. pct using a combination of high energy ball milling and spark plasma sintering (SPS) and systematically investigated their microstructure, mechanical properties, and sliding wear behavior. The results show that the Ti95Cu5 alloy consists of Ti2Cu precipitates uniformly distributed in an α-Ti matrix. This particular microstructure results in excellent mechanical properties, including a compressive yield strength of up to 1593 MPa, compressive strength of over 2400 MPa, and fracture strain of up to 26.8 pct. Conversely, the bulk Ti75Cu25 alloy consists mainly of Ti2Cu with a small amount of α-Ti and exhibited a slightly higher yield strength but reduced compressive strength and fracture strain. The hardness and yield strength of the Ti-Cu alloys were approximately three times and one order of magnitude higher, respectively, than those of commercially pure Ti. Sliding wear tests reveal that the wear mechanism of the ultra-fine-grained Ti-Cu alloys is distinct from that of CP-Ti and that the wear resistance is enhanced with increasing Ti2Cu content.

Anti-bacterium influenced corrosion effect of antibacterial Ti-3Cu alloy in Staphylococcus aureus suspension for biomedical application

Titanium and titanium alloys have been widely used as dental and orthopedic materials. The infection and the bacterium influenced corrosion both are concerned problems. Ti-3Cu alloy exhibits strong antibacterial properties against E. coli and S. aureus. The strong antibacterial properties of Ti-3Cu provides with a potential new method to reduce the bacterium influenced corrosion. S. aureus suspension was selected to simulate a serious bacterial condition. The corrosion behavior of Ti-3Cu alloy in S. aureus suspension was investigated by an electrochemical testing and an immersion test in comparison with pure titanium. Electrochemical results showed that Ti-3Cu exhibited a much better anti-corrosion property than cp-Ti in S. aureus suspension. Surface observation demonstrated that no corrosion pit was observed on Ti-3Cu alloy after 30 days immersion in the suspension while lots of corrosion pits were found on cp-Ti. The biofilm formation on the surface was observed by scanning electronic microscopy (SEM) in different periods. It has been revealed that S. aureus could grow and gather on the surface of cp-Ti to form biofilm after 18 h immersion, but only several bacteria were found on Ti-3Cu alloy even after 24 h immersion, displaying that Ti-3Cu alloy exhibits very strong anti-adhesion properties against S. aureus. It was concluded that Ti-3Cu performs a super anti-corrosion property due to the strong anti-adhesion property, in which Ti2Cu precipitate plays a critical role.

Yield of Binary Ti-Cu and Ti-Mn Alloys Produced via Powder Metallurgy

High strength, low density, good corrosion resistance and biocompatibility is the combination of properties that Ti and its alloys can provide for engineering applications. Its costs are the most important limiting factor for the widespread use of Ti. Cost reduction for Ti alloys can derive from the use of cheaper alloying elements as well as the use of alternative manufacturing techniques. In this study binary Ti-X alloys (where X = Cu or Mn) were formulated and produced using the conventional powder metallurgy route of pressing and sintering. These chemical elements were selected because they are β stabilisers and can be used to create α+β Ti alloys. The study shows that with the techniques and processing parameters used handable products without delamination can be pressed. Moreover, chemically homogenous materials with density and mechanical property values comparable to those of other wrought-equivalent Ti alloys produced via powder metallurgy were achieved.

CNTs/Cu-Ti composites fabrication through the synergistic reinforcement of CNTs and in situ generated nano-TiC particles

CNTs/Cu-Ti composites were fabricated successfully by spray pyrolysis, low energy ball milling and subsequent hot pressing (HP). Microstructure and mechanical properties of the composites were characterized by SEM, EDS, HRTEM, XRD, hardness and tensile tests. The results reveal that in situ generated nano-TiC particles, as a transition phase from CNTs to Cu-Ti matrix, which played a “rivet” role in enhancing the interfacial bonding between the CNTs and Cu-Ti matrix is formed in the composites. Consequently, mechanical properties of the CNTs/Cu-Ti composites are enhanced compared with alloy matrix, and an optimal balance between elevated ultimate tensile strength and impressively larger plastic deformation is achieved by adding 0.4 wt% CNTs in the composites. (ultimate tensile strength (UTS) 352 MPa, elongation 28.2%, the UTS is 39% higher than that of the Cu-Ti alloy, and the ductility increased significantly by 62%.) Finally, strengthening and toughening mechanisms are discussed. This study provides new insights into the interface structure and strength-ductility in metal-matrix composites.

In-situ microstructural observation of Ti-Cu alloys for semi-solid processing

The semi-solid processing of metallic alloys strongly depends on the microstructural features exhibited by the raw material. Consequently, many characterization techniques have been used to elucidate semi-solid microstructures. In the present work, high-temperature laser-scanning confocal microscopy (HT-LSCM) was used to characterize Ti-Cu alloys intended for thixoforming. During the reheating stage, this in-situ technique enabled us to observe the Ti-β grains formed through the reverse eutectoid transformation. Furthermore, the results showed that thermomechanical treatment was primarily responsible for breaking up the dendritic microstructure. The liquid formation and peritectic temperature were easily determined via the HT-LSCM investigation. Prior to the reverse peritectic reaction, which corresponds to the onset of equilibrium melting, we obtained experimental evidence of the melting of non-equilibrium phases that originated via segregation during solidification. Finally, it was possible to qualitatively study the coarsening mechanisms that occurred in the semi-solid state. Irrespective of the alloy composition (liquid fraction), both Ostwald ripening and coalescence occurred during the isothermal heat treatments. Based on the obtained results, HT-LCSM can be considered a valuable technique for the characterization of thixotropic alloys.

High Strength and High Electrical Conductivity Cu-Ti Alloy Wires Fabricated by Aging and Severe Drawing

We designed an optimal procedure to prepare Cu-Ti alloy wires with an excellent combination of strength and electrical conductivity, by drawing conventional peak-aged alloys as well as over-aged ones. When drawing the peak-aged alloy, which exhibited the maximum hardness after aging and a low electrical conductivity, the strength of the wires increased rapidly in the initial stage of drawing but then saturated on further drawing. On the contrary, when drawing the over-aged alloy of inferior hardness but superior electrical conductivity, the strength increased steadily through drawing and eventually exceeded the value of the wires drawn from the peak-aged alloy. Also, the electrical conductivity of the wires drawn from the over-aged alloy was always much greater than that from the peak-aged alloy. Thus, we demonstrated that the procedure of over-aging and then drawing severely is able to enhance both the strength and the electrical conductivity for the Cu-Ti alloys, rather than the conventional peak-aging and drawing process. Noted that the performance of the wires drawn from the over-aged alloy is comparable with that of commercial Cu-Be wires, which are considered to possess the combination of greatest strength and conductivity in Cu-based alloys.

Improved Corrosion Resistance on Selective Laser Melting Produced Ti-5Cu Alloy after Heat Treatment.

A Ti-5Cu alloy produced by selective laser melting exhibits a nonuniform Ti2Cu phase structure, which contains a small amount of α' phase in melt pool boundaries thereby resulting in reduced corrosion resistance. The heat-treatment process proposed in this work eliminates the deleterious effect of α' phase and the Ti2Cu phase is refined using different cooling rates, which improves the corrosion resistance. The electrochemical results indicate that the heat-treated Ti-5Cu samples have similar corrosion behavior to pure CP-Ti. A slower cooling rate produces a larger spacing between the Ti2Cu phases in the microstructure of the sample, resulting in higher corrosion resistance. The corrosion behavior of SLM-produced Ti-5Cu and heat-treated counterparts with different microstructure are detailed discussed.