Cu-Ti Alloys Research Articles

Fabrication of Dual-Phase Strengthened Cu–Ti Alloy Sheets

Fabrication of Dual-Phase Strengthened Cu–Ti Alloy Sheets

Improvement of micro/nano-structure and corrosion resistance of TiCu alloy by addition of tin and their Sr-hydroxyapatite coating

This study explores the influence of tin (Sn) content on the properties of Ti7CuXSn (X = 2, 7, and 15 wt%) alloys, in both as-cast and heat-treated conditions. The investigation reveals that an elevated Sn content within the Ti7Cu alloy results in the formation of finer grain structures. Rapid quenching processes lead to the development of an ultrafine martensitic structure and the formation of (Ti,Sn)2Cu intermetallic compounds within the Ti7CuXSn alloys. Subsequent heat treatment processes induce the transformation of the ultrafine martensitic structure into a coarser one, accompanied by an increase in the volume fraction of (Ti,Sn)2Cu. X-ray diffraction (XRD) analysis validates the presence of α/α'-Ti(Sn,Cu) phases and (Ti,Sn)2Cu intermetallics across all alloy compositions. The Ti7Cu15Sn alloy demonstrates higher microhardness, primarily attributed to its smaller grain size, reduced lamellar spacing, and increased volume fraction of (Ti,Sn)2Cu. Furthermore, all specimens exhibit heightened microhardness following heat treatment due to the martensitic structure with heterogeneous and homogeneous nucleation of (Ti,Sn)2Cu intermediate growth. Electrochemical analysis reveals an enhanced corrosion resistance in the Ti7Cu15Sn alloy, attributed to its elevated Sn content. Nonetheless, the as-cast Ti7Cu15Sn alloy displays superior corrosion resistance, albeit with a marginal reduction in electrochemical performance following heat treatment. Surface characterization signifies the formation of a uniform oxide film, underscoring commendable corrosion resistance in both as-cast and heat-treated Ti7CuXSn alloys. Additionally, the study investigates the deposition of strontium (Sr)-doped ceramic coatings on as-cast Ti7Cu15Sn alloys. It is demonstrated that higher current density parameters yield denser and more crystalline Sr-HA coatings. Energy dispersive spectroscopy (EDS) mapping confirms the successful incorporation of Sr into the coating, showcasing its potential for applications in the field of biomedicine. Thus, this investigation highlights the significant impact of Sn content on microstructural refinement, enhancements in mechanical properties, and improved electrochemical performance within Ti7CuXSn alloys. These findings offer valuable insights for the design and optimization of alloy performance in diverse applications.

A Novel Microstructure of Cu-Ti Alloy with Ultrahigh Electrical Conductivity and Strength

A Novel Microstructure of Cu-Ti Alloy with Ultrahigh Electrical Conductivity and Strength

High strength and high conductivity Cu-Ta composites fabricated by powder metallurgy

Copper matrix composites with excellent comprehensive properties can be obtained by combining copper and copper alloys with refractory metals. Cu-Ta and CuCrNb-Ta composites were fabricated by powder metallurgy. The hardness and conductivity of cold-rolled CuCrNb-1Ta, CuCrNb-3Ta, and CuCrNb-6Ta composites were 102.2 HV and 90.6% IACS, 120.4 HV and 88.0% IACS, 118.6 HV and 87.5% IACS, respectively. Cr2Ta was detected on the surface of Ta particles in the sintered CuCrNb-Ta composites, and a Ta@Cr2Ta core-shell structure formed. The mechanical properties and conductivity of the CuCrNb-Ta composites in sintered state + cold rolling treatment + aging treatment are higher than those of Cu-Ta alloys under the coordinated action of solution strengthening and precipitation strengthening. These findings are conducive to the development of high-strength copper-based composites.

Wetting of Al2O3 by Cu-xTi alloys at 1373 K

Wetting of Al2O3 by molten Cu-xTi alloys with wide composition range was deeply studied. The results show that the precipitation of TiO at the interface is depended on the Ti concentration in the alloys as well as the oxygen partial pressure in the atmosphere. When Ti concentration is lower than the critical Ti concentration, the wettability of the system is mainly determined by the precipitated TiO and the adsorption of Ti-O clusters at the interface; conversely, it is mainly determined by the adsorption of Ti-O clusters on the surface of alumina. For the spreading dynamics of: Cu-Ti alloys on the sapphire surface, the existence of two stages were observed: firstly, an initial fast spreading stage, which is mainly limited by the reaction rate of TiO precipitation; followed by a later slow spreading stage, which is mainly limited by the precipitation reaction of Al2O, and exhibits a stepwise spreading characteristic.

Influence of alloying elements and composition on microstructure and mechanical properties of Cu-Si, Cu-Ag, Cu-Ti, and Cu-Zr alloys

This study aims to quantitatively compare the effects of alloying elements on the microstructures and mechanical properties of Cu–Si, Cu–Ag, Cu–Ti, and Cu–Zr binary alloys over an alloying content range up to 2 wt%. The alloys were produced using vacuum arc melting, followed by homogenization and cold-rolling into plates. Subsequently, the annealing response of the cold-rolled plates was examined over a temperature range of 200–700 °C. The as-cast alloys show distinct microstructural features attributable to the alloying elements. Following the homogenization and cold-rolling processes, substantial microstructural transformations were observed. The analysis of mechanical properties revealed that solid solution hardening played a dominant role in increasing strength in Cu–Si alloys. Cu–Ag alloys displayed a minor increase in strength with alloying content, implying the influence of Cu–Ag precipitates on strength. Conversely, Cu–Ti and Cu–Zr alloys demonstrated remarkable strength improvements due to the presence of intermetallic precipitates and grain size reduction. While all other alloys displayed an inverse relationship between strength and elongation with increasing alloying content, the Cu-Si alloys exhibited a simultaneous enhancement of both strength and elongation. This effect can be attributed to the twinning-induced plasticity, brought about by the reduction of stacking fault energy in Cu through the addition of Si.

Selective photoelectrocatalytic CO2 reduction to ethanol using nanotubular oxides grown on metastable Ti-Cu alloy

The photoelectrochemical conversion of CO2 to C2 products such as ethanol is a topic of much current interest and relevance for decreasing the amount of greenhouse gases in the atmosphere. Here, the photoelectrocatalytic selectivity for the CO2 reduction reaction on Ti-O-Cu nanotubes grown on bimetallic alloys (Ti-xCu; x = 0.5, 5.5 and 10 at. %) was investigated. The product selectivity in the CO2 reduction reaction was found to depend on the effects of composition and distribution of the oxidant species along the nanotubes. This behavior was coordinated by the substrate phases obtained from Ti-Cu alloys subjected to different heat treatments (annealed followed by rapid cooling – quenched (Q) or annealed with controlled cooling (A)). A nanotubular (Nt) oxide layer was grown on these substrates and the influence of metastable (quenched) or equilibrium (annealed) phases was related to the diffusion of the copper species. The two types of electrodes were compared in terms of their relative proclivity toward CO2 photoreduction. Methanol was produced as the dominant reduction product on Nt/Ti-10Cu (A). On the other hand, Nt/Ti-10Cu (Q) produced a respectable yield and selectivity for ethanol, reaching 2.32 mmol/L of ethanol. In a broader vein, this study demonstrates the importance of surface defects in an active heterogeneous photocatalyst and provides insights into the key parameters for the precursor design, selection, and optimal performance of materials for the CO2 reduction reaction leading to C2 compounds.

Phase transformation pathways in a Ti-5.9Cu alloy modified with Fe and Al

Titanium alloys have been gaining importance in various industries due to their advantageous combination of strength, low density, excellent corrosion/oxidation resistance, and superior mechanical properties at elevated temperatures. Recently, eutectoid Ti–Cu alloys have been explored as promising candidates for advanced processes. This work investigates the effects of Fe and Al on a Ti-5.9Cu alloy using multi-scale characterization techniques. While Fe acts as a β-stabilizing element (despite being a sluggish eutectoid former), Al acts as an α-stabilizer. This work focuses on the effects of combined addition of these elements, studied in different heat treatment conditions. The results show that a fine, equiaxed microstructure is obtained in the binary Ti-5.9Cu alloy, whereas the addition of 2 wt% Fe, or 2 wt% Fe combined with 2 wt% Al to the Ti-5.9Cu alloy deteriorates the effect of grain refinement and coarse, columnar grains result and a small amount of β-phase is retained. Further, the microstructure resulting from the eutectoid decomposition is altered dramatically from a lamellar pearlitic in the binary alloy to a lath-like α-phase with diverse decomposition products in the ternary and quaternary alloys accompanied by increasing hardness values. Evaluation of the α misorientation suggests that a substantial amount of non-Burgers α is present in the Ti-Cu alloy in contrast to the results of the ternary and quaternary alloys. The observed Cu-rich intermetallic compound was identified as Ti2Cu phase with off-stoichiometric composition. Results obtained explain how adding either Fe or Fe and Al leads to substantial hardening.

Characterizing stable nanocrystalline Cu-Ta behavior and failure dynamics under extremes of strain rate, strain, temperature and pressure by modified dynamic tensile extrusion

This work presents characterization of thermo-mechanically stable, bulk nanocrystalline (NC) Cu-Ta alloys under a combination of extreme states using high-temperature, dynamic tensile extrusion experiments. The NC Cu-Ta was subjected to high dynamic strain rates up to 105/s, large plastic strains of 100–500 %, and high homologous temperatures greater than 50 %TM. This combination of thermo-mechanical conditions provides a unique look at how these extremely stable microstructures can accommodate and reconfigure under situations where dislocation activity is the most extreme, given constitutive relationships between strain rate, dislocation nucleation, and plastic work. Elevated temperature tests results reveal NC Cu-1Ta alloys are capable of forming a coherent jet, (25 mm in length by 1.8 mm in diameter) as it accelerates out of the die after being dynamically extruded. Microstructural analysis reveals that unlike previous reports on conventional un-stabilized nano or near nano-grained Cu, NC Cu-Ta alloys behave differently. They do not undergo grain coarsening via a nucleation and growth process, but rather behave identically to that of coarse-grained Cu. The NC grains elongate along the extrusion direction and at the same time shrink in diameter and develop a <111> type texture. Ultimately, the occurrence of premature dynamic failure was attributed to the inherent constraints posed by processing defects during synthesis.

Immunomodulatory effect of Ti-Cu alloy by surface nanostructure synergistic with Cu2+ release

The inflammatory response induced by implant/macrophage interaction has been considered to be one of the vital factors in determining the success of implantation. In this study, TiCuNxOy coating with an immunomodulatory strategy was proposed for the first time, using nanostructured TiCuNxOy coating synthesized on Ti-Cu alloy by oxygen and nitrogen plasma-based surface modification. It was found that TiCuNxOy coating inhibited macrophage proliferation but stimulated macrophage preferential activation and presented an elongated morphology due to the surface nanostructure. The most encouraging discovery was that TiCuNxOy coating promoted the initial pro-inflammatory response of macrophages and then accelerated the M1-to-M2 transition of macrophages via a synergistic effect of fast-to-slow Cu2+ release and surface nanostructure, which was considered to contribute to initial infection elimination and tissue healing. As expected, TiCuNxOy coating released desirable Cu2+ and generated a favorable immune response that facilitated HUVEC recruitment to the coating, and accelerated proliferation, VEGF secretion and NO production of HUVECs. On the other hand, it is satisfying that TiCuNxOy coating maintained perfect long-term antibacterial activity (≥99.9%), mainly relying on Cu2O/CuO contact sterilization. These results indicated that TiCuNxOy coating might offer novel insights into the creation of a surface with immunomodulatory effects and long-term bactericidal potential for cardiovascular applications.

Quantifying the solute-induced additional repulsive force between two partials of pure screw dislocations

The interactions between two partials of a pure screw dislocation are closely associated with numerous deformation mechanisms in face-centered cubic metals. However, the classical method for quantifying the repulsive force between two partials fails for some binary alloys or the newly emerging medium/high entropy alloys due to the presence of additional forces arising from the randomly distributed solute atoms. This paper presents a study on the interaction between two curved partial dislocations, taking into account the effects of solute-induced dislocation perturbations through the use of elastic mechanics and atomistic simulations. The theoretical analysis reveals the existence of an additional repulsive force between two curved partials, which monotonically increases with the average power spectrum of perturbation amplitudes, i.e., Δf∝⟨(Cn)2⟩. Atomistic simulations of CuAg and CuTa alloys further demonstrate that the average power spectrum exhibits a linear dependence on the solute fractions, denoted as ⟨(Cn)2⟩∝χ, which bears resemblance to the relationship between power spectrum and temperature, i.e., ⟨(Cn)2⟩∝T in the case of temperature-induced fluctuations. Therefore, it can be concluded that the additional repulsive force is linearly proportional to the solute fractions in binary alloys. The methodology presented in this study can be easily applied to other face-centered cubic (FCC) alloys as well as multicomponent solute-strengthened alloys.

Effects of Zr addition on the microstructures, mechanical properties and thermal stability of Cu-Ta alloys

In this work, Cu-1.4 wt%Ta-Zr alloys with different Zr content (0, 0.1, 0.2 and 0.5 wt%) were fabricated by mechanical alloying combined with spark plasm sintering. The effect of Zr addition on the microstructures, mechanical properties and thermal stability of Cu-Ta alloy were characterized. Cu-Ta alloys composes of ultrafine equiaxed grains along with the uniformly dispersion of semi-coherent Ta nanoclusters and incoherent Ta coarse particles. As Zr is introduced into Cu-Ta alloy, the Ta precipitates were effectively refined, especially for the reduction of Ta coarse particles. The significant refinement effect of the grains is realized when Zr content reaches 0.2 wt%, and high-proportioned nano-sized grains are facilitated to form, along with the activation of a lot of twins and the formation of intermetallic composed of Cu and Zr. The dislocation density and strength increase remarkably with the increase of Zr content, and the highest strength (499 MPa for yield strength and 600 MPa for ultimate tensile strength) is achieved as the Zr content is up to 0.2 wt%. Compared with Cu-Ta alloy (382 MPa for yield strength and 560 MPa for ultimate tensile strength), the significant increment of 31% for the yield strength is successfully realized by Cu-Ta-0.2 wt%Zr alloy. Cu-Ta-0.2 wt%Zr alloys exhibit the excellent thermal stability, and the hardness keeps stable even the sample was annealed at 700 °C for 300 h, showing superior microstructural stability in comparison with Cu-Ta alloy (∼4.5% reduction of the hardness after 300 h at 700 °C). The softening temperature of Cu-Ta-0.2 wt%Zr alloy is up to 1028 °C (1022 °C for Cu-Ta alloy) along with higher hardness than that of Cu-Ta alloy at the same annealing temperature. This study provides a new way to fabricate dispersion strengthened Cu alloys with high strength, exceptional thermal stability and softening resistance, which have great potential application value in the field of future fusion reactor.

Enhanced mechanical property by introducing bimodal grains structures in Cu-Ta alloys fabricated by mechanical alloying

Dispersion-strengthened copper alloys can achieve ultra-high strength, but usually at the expense of ductility. In this study, a strategy for overcoming strength-ductility tradeoff of Cu alloys is realized through the introduction of bimodal grains structures. Cu-Ta alloys with only 0.5 at.% Ta content were successfully prepared by mechanical alloying combined with spark plasm sintering. The samples prepared by one-step and two-step ball milling methods are named as Cu-Ta (Ⅰ) and Cu-Ta (Ⅱ), respectively. The microstructural characterizations revealed that ultra-fine equiaxed grains with uniformly dispersed Ta precipitates were obtained in the Cu-Ta alloys. High strength of 377 MPa for yield strength together with elongation of ∼8% was obtained in Cu-Ta (Ⅰ). Bimodal grains structures composed of fine-grain zones and coarse-grain zones were successfully introduced into Cu-Ta (Ⅱ) by a two-step ball milling approach, and both yield strength (463 MPa) and elongation (∼15%) were significantly synergistic enhanced. The hardness values of both Cu-Ta (Ⅰ) and Cu-Ta (Ⅱ) were almost kept nearly constant with the increase of annealing time, and the softening temperatures of Cu-Ta (Ⅰ) and Cu-Ta (Ⅱ) are 1018 and 1013 °C, reaching 93.9% and 93.5% Tm of pure Cu (1083 °C), respectively. It reveals that the Cu-0.5 at.% Ta alloys exhibit excellent thermal stability and exceptional softening resistance. Ta nanoclusters with semi-coherent structures play an essential role in enhancing the strength and microstructural stability of alloys. Bimodal structures are beneficial to the activation of back stress strengthening and the initiation and propagation of microcracks, thus obtaining the extraordinary combination of strength and elongation. This study provides a new way to fabricate dispersion-strengthened Cu alloys with high strength, high elongation, excellent thermal stability and softening resistance, which have potential application value in the field of the future fusion reactor.

Temperature-Dependence of Mixing Properties of Cu-Ti Liquid Alloy

In this study, the temperature-dependence of thermodynamic and surface properties of Cu-Ti binary liquid alloy were studied. In thermodynamic properties, excess Gibbs free energy of mixing, enthalpy of mixing, excess entropy of mixing, and activity of the system were computed at 1873 K. The surface properties were analyzed by computing the surface tension and surface concentration of the system. Thermodynamic properties were computed in the framework of the Redlich-Kister polynomial, and the surface properties were computed using the Butler model. At its melting point, the system exhibited a tendency for the formation of compounds, and as the Cu concentration was increased, the surface tension of the system gradually decreased. The excess Gibbs free energy of mixing, activity and surface tension of the system were also computed at different temperatures, in the range 1873-2173 K. With the increase in temperature of the system, the compound forming tendency of the system gradually decreased.

High-Resolution Composition Wave Characterization in Cu-Ti Alloys using Aberration Corrected STEM.

High-Resolution Composition Wave Characterization in Cu-Ti Alloys using Aberration Corrected STEM.

Stability of the metastable β'-Cu4Ti phase in Cu[sbnd]Ti alloys: Role of the Ti content

The stability of the metastable β'-Cu4Ti phase is a crucial factor for the electrical conductivity of CuTi alloys. Determining the factors that influence the stability of the β'-Cu4Ti phase and the relationship between the β'-Cu4Ti phase and the electrical conductivity of CuTi alloys is a prerequisite to improve their electrical conductivity. In this study, the stabilities of the β'-Cu4Ti and β-Cu4Ti phases were investigated by first-principles calculations combined with experimental characterization. When the Ti content of the β'-Cu4Ti phase is greater than or equal to 19 at.%, its stability is lower than that of the β-Cu4Ti phase, resulting in instability of the β'-Cu4Ti phase and dissolution of Ti atoms back into the Cu matrix. This is the main reason why it is difficult to improve the electrical conductivity of CuTi alloys when the β'-Cu4Ti phase is the main strengthening precipitate.

Enhanced antibacterial activity, corrosion resistance and endothelialization potential of Ti-5Cu alloy by oxygen and nitrogen plasma-based surface modification

Antibacterial Ti-5Cu alloy is a promising substitute material for Ti-made cardiovascular implants, so its surface engineering is crucial to expediting clinical implementation. Given the antibacterial and cardiovascular biological benefits of Cu2+ and titanium-nitride-oxide (TiNxOy) coatings, a Cu2O/CuO-TiNxOy coating with upregulated Cu2+ release was successfully deposited on Ti-5Cu alloy for the first time using oxygen and nitrogen plasma-based surface modification. The superhydrophilic and nanostructured Cu2O/CuO-TiNxOy coating had a dense structure and was well bonded to the substrate, resulting in enhanced corrosion resistance, while CuO/Cu2O in the coating released Cu2+ faster than Ti2Cu phase in the matrix. More gratifying, the coating demonstrated perfect antibacterial properties (R > 99.9% against S. aureus), owing primarily to direct contact sterilization of Cu2O/CuO. The most encouraging phenomenon was that the coating dramatically accelerated HUVEC adhesion (1.4 times), proliferation (RGR: 106%–116%), and particularly migration (RMR: 158%–247%) compared with the control Ti. The coating extract also significantly stimulated in vitro angiogenesis capacity. The rapid endothelialization for Cu2O/CuO-TiNxOy coating was attributed to the surface nanostructure and Cu2+/NO2− release, which upregulated the angiogenesis-related gene expression of HIF-1α, VEGF, and eNOS to increase VEGF secretion and NO production. All of the findings indicated that the Cu2O/CuO-TiNxOy coating could enhance the corrosion resistance, antibacterial properties, and endothelialization potential of Ti-Cu alloy, displaying great clinical potential in cardiovascular applications.

Achieving optimal wear performance for highly-eutectic Cu-Ti alloys via the liquid-solid reaction approach

A series of Cu-Ti alloys have been prepared by the liquid-solid reaction approach at a high vacuum environment. Resultant solidified microstructures have demonstrated highly-eutectic features, which are mainly composed of typical CuTi and CuTi2 phases. Vicker hardness tests have shown that the hardness values of CuTi and CuTi2 are 304 ± 15 HV and 683 ± 27 HV, respectively. Quantitative phase identification has indicated that, as the Ti content increases from 53 at% to 61 at%, the volume fraction of eutectic structure increases initially but decreases afterward, which are 18.8 ± 3.4%, 94.6 ± 3.5% and 54.4 ± 4.5%, respectively. The optimal wear performance has been achieved when the Ti content reaches 57 at%, which is concurrent to the highest volume fraction of the eutectic structure (94.6 ± 3.5%). Our findings may pave a viable yet economic way of fabricating wear resistant alloys in a controllable manner. Data availabilityNo data was used for the research described in the article.

Laser directed energy deposited, ultrafine-grained functional titanium-copper alloys tailored for marine environments: Antibacterial and anti-microbial corrosion studies

The microorganism-rich nature of the ocean imposes great challenges to the structural integrity of metals over their service lifespan, including titanium (Ti) alloys, which are usually prone to microbiologically influenced corrosion (MIC). So, multifunctional anti-MIC Ti alloys need to be developed and studied. This paper investigates the effect of copper (Cu) concentration on the MIC resistance of a series of additively manufactured, ultrafine-grained Ti-xCu (x= 3.5, 6.5 and 8.5 in wt.%) alloys. The dependence of the corrosion resistance and MIC resistance on the Cu concentration of Ti-Cu alloy is interpreted considering all conceivable mechanisms. The mechanisms for excellent corrosion resistance of Ti-Cu alloy in seawater are attributed to the strong passive film and small surface potential difference between phases. Microstructural characterization reveals that uniformly distributed, nanosized Ti2Cu phase led to increased reactive oxygen species in the bacterial membrane, which is the root reason for the superb anti-bacterial property (99.2%) for Ti-8.5Cu. Compared to pure Ti and Ti-6Al-4V, Ti-8.5Cu alloy features both high strength (yield stress > 1000 MPa) and the best MIC resistance (97.5%). The combination of such balanced properties enables this functional 3D printed Ti-Cu alloy to become an ideal material for load-bearing applications in the marine environment.

Ti-Cu積層造形合金における熱処理による析出形態の制御と機構解明

Intermetallic compounds (IMCs), known for their hardness, play an important role in the precipitation strengthening of alloys. However, precipitation in excessive amounts or as large particles can result in embrittlement of the material. Thus, controlling the distribution of IMCs among the matrix is crucial for the design of strong and ductile alloys. In this research, a supersaturated Ti-Cu alloy formed by Laser Powder Bed Fusion (L-PBF) was heat-treated at different phase regions to produce lamellar, network, and dispersed distributions of Ti2Cu IMC precipitates. To comprehensively understand the formation mechanisms of each IMC distribution structure, in-situ microstructure observation was performed during the heat-treatments. The lamellar IMC structure obtained from heat treatment above the beta-transus temperature, was found to derive from the rejection of Cu atoms towards the boundaries of lamellar alpha grains formed during cooling. The network IMC structure obtained from heat-treatment in the α+β phase region involved the formation of a Cu-rich β-Ti layer between α-Ti grains during heating, and subsequent precipitation of Ti2Cu into an α-encapsulating network upon cooling. Finally, the dispersed structure of IMCs was observed to result from regular nucleation and growth of Ti2Cu during heat treatment in the α+IMC region.