4Cr 4Ti Alloy Research Articles

Investigations of impact force of the Al–Fe–Cr–Ti alloy by high-velocity compaction

Aluminum alloy materials are the primary choice for lightweight components. High-velocity compaction (HVC) enhances the density of diverse materials. This study utilizes HVC to enhance the density of aluminum alloy. This work examined the influence of compaction velocity, response time (Γ), compaction times, and height-diameter ratio on the impact force of HVC. The maximum force increased linearly with higher compaction velocity, reaching up to 700 kN when the compaction velocity was 9.4 m/s, alongside achieving a peak relative density of 95%. Investigation into the influence of compaction times on the impact force of HVC revealed that the state of powders were critical factors affecting the magnitude of impact force. When the total compaction energy was consistent, the maximum force from double strokes was observed to be lower compared to single stroke. Furthermore, in double strokes with the same second stroke of 55 mm, it was noted that the maximum force increased with higher velocity during the initial compaction. Additionally, both the maximum force and green density decreased as the height-diameter ratio increased. When the height-diameter was 0.4, the maximum force and green density were higher 251 kN, 0.22 g/cm3 than that of 1.2.

Defect dynamics studies during heat treatments in plastically deformed metals predicted for nuclear applications

We report on defects dynamics during heat treatment in plastically deformed metallic materials using positron annihilation lifetime spectroscopy carried out on the intense pulsed positron beam. The conducted experiment allowed us to observe the changes in the concentration and sizes of vacancy-like defects observed during in situ annealing. We monitored heat treatments up to 300 °C in hydrostatic extruded Ti and cavitation peened V–4Cr–4Ti alloy. We were able to track the recovery processes in Ti and redistribution of large voids at the surface of cavitation peened V–4Cr–4Ti alloy. The relaxation time during recovery was about 20 min. Performed experiments show that in cold-worked metallic materials significant changes in vacancy clusters concentrations occur at mildly elevated temperatures. The presented results give opportunity to the application of in situ observation of defects dynamic to similar problems related to thermomechanical processing of metallic materials.Graphical abstract

Effect of Cr content on the microstructure and mechanical properties of Ti–Cr alloys manufactured by laser directed energy deposition

Titanium (Ti) and titanium alloys have been increasingly used in fixed and removable prostheses and aerospace bearing materials because of its excellent biocompatibility, corrosion resistance and mechanical properties. Cr element is often added to titanium alloys as a solid solution strengthening element. However, the content of Cr was restricted in the commercial titanium alloy to avoid β-flecks and deterioration of mechanical performance because of the strong segregation of Cr. A series of homogeneous Ti-xCr (x = 6, 8.5, 10, 13.4, 15 wt%) binary alloys near the eutectoid point were manufactured by laser directed energy deposition. The phase composition and morphology, mechanical properties and deformation mechanism were investigated. It was demonstrated that the eutectoid reaction of additive manufacturing Ti–Cr alloy has been suppressed. Hypoeutectoid Ti-xCr alloys (x = 6, 8.5, 10 wt%) obtained microstructures consisting of α and β phase. The Ti-xCr alloy with eutectoid compositions (x = 13.4 wt%) obtained a microstructure mainly composed of ω and β phase. And hypereutectoid Ti-xCr alloy (x = 15 wt%) exhibited a fully β microstructure. For α+β type Ti–Cr alloys, and the average width of α lath decreased from 868 nm to 157 nm with Cr content increased from 6 wt% to 10 wt%. Correspondingly, the α+β type Ti–10Cr alloy presented a good combination of strength (an ultimate tensile strength of 1042 MPa) and ductility (an elongation of 7.1 %). Then, a high density of ω phase was found in the Ti-13.4Cr alloy with eutectoid compositions, which leads to its brittleness. Due to the solid solution of high concentration of Cr, β-type Ti–15Cr alloy obtained a high ultimate tensile strength of 941 MPa. Furthermore, stress-induced ω phase and {112}<111> twinning formed during the deformation, which helps to accommodate stress concentration, thereby the β-type Ti–15Cr alloy can maintain high ductility (20.3 %).

Local structural changes in V–Ti–Cr alloy hydrides with hydrogen absorption/desorption cycling

Vanadium-based solid solution alloys potentially serve as safe, high-capacity hydrogen storage materials. Low-vanadium-concentration alloys have low durability, and their hydrogen absorption and desorption amounts decrease by 20 % after 100 cycles. In this study, we conducted reverse Monte Carlo modeling on X-ray diffraction patterns and neutron pair distribution functions of the hydrogen-absorbed and desorbed samples of a V0.10Ti0.36Cr0.54 alloy to analyze the variations in the local structure. The local structure surrounding the hydrogen atom in the hydrogen-absorbed phase exhibited minimal changes. In contrast, hydrogen occupied both tetrahedral and octahedral sites of the hydrogen-desorbed phase almost equally during the early cycles; however, the amount of hydrogen occupying the tetrahedral sites increased with the number of cycles. It is speculated that hydrogen absorption and desorption cycling induced grain refinement and/or introduced dislocations, which altered both the amount of hydrogen and the sites occupied in the desorbed phase, thereby decreasing the hydrogen storage capacity.

Effect of Ti on the microstructure and properties of Cu–Cr alloy

Cu–Cr–Ti alloy was successfully prepared by vacuum melting, solution treatment at 960 °C for 1 h, 80 % cold rolling and aging at 500 °C for 1 h. The effect of Ti content on the microstructure was characterized by Scanning electron microscope (SEM) and Transmission electron microscope (TEM). Their tensile strength, electrical conductivity, thermal stability, wear resistance and arc erosion resistance were also measured. The results showed that Ti can form the Ti0.77S phase with S, which can prevent the occurrence of sulfur embrittlement. And Ti can segregate around the Cr precipitates, hindering their growth. Therefore, the tensile strength, hardness, high temperature softening resistance, wear resistance and arc erosion resistance improved with the increase of Ti content. But the electrical conductivity decreased sharply since Ti was mainly solidly dissolved in the matrix. What's more, the electrical conductivity decreased sharply and other properties did not improve when the content increased from 0.066 wt% to 0.098 wt%, that is, the comprehensive performance was the best when the Ti content was 0.066 wt%. The tensile strength was 551 MPa, electrical conductivity was 78.3%IACS and the friction coefficient was 0.33. This work provides effective ideas for preparing copper alloys with desired properties.

Dislocation-mediated migration of the α/β interfaces in titanium

Interphase boundaries are essential in the deformation and phase transformations in titanium (Ti) alloys. While static structures of semicoherent α/β interfaces in various Ti alloys have been carefully examined, their migration behavior at atomic scales is far less clear. In this study, we employed molecular dynamics simulations to investigate the migration of the semicoherent α/β interface in pure Ti. The interface migration behavior shows a shear-coupled feature with the interface dislocation glide and a macroscopic shear. The simulation reveals that both the glide direction of the dislocations with respect to the interface and the dislocation spacing strongly influence the migration rate, and the low-index glide plane of the interface dislocation plays a minor role. The dependence of interface mobility on temperatures confirms the critical role of thermal activation during the interface migration, especially for activating the interface dislocation glide. Furthermore, the shear-coupled interface migration driven by element partition is simulated using a newly developed Ti-Mo potential, consistent with the displacive-diffusional features previously observed in the surface precipitates. The simulated interface migration mode is validated by comparing it with the crystallography features of surface precipitates in a Ti-Cr alloy. The interface energy and mobility obtained from simulations further explain why the distinctive crystallographic features of the surface precipitates observed experimentally are favored over other candidate interfaces. The present study has explored an approach for systematically examining thermodynamic and kinetic factors governing the development of phase transformation crystallography at different temperatures and chemical driving forces.

High-temperature tensile properties of an aluminum quasicrystal-forming alloy manufactured by laser powder bed fusion

Normalized tensile samples of Al–4Fe–3Cr–2Ti (wt.%) alloy were successfully fabricated by laser powder bed fusion (LPBF) additive manufacturing. The alloy's tensile properties and microstructure were investigated at room and high-temperature (up to 500 °C). This Al–Fe–Cr–Ti alloy exhibits exceptional thermal stability and outstanding mechanical performance at temperatures of up to 500 °C. A particularly interesting feature is the alloy's yield strength values, which reach ∼300 MPa at 300 °C and ∼180 MPa at 400 °C. The outstanding mechanical behavior of this alloy at high temperatures is attributed to the in situ precipitation of ultrafine icosahedral quasicrystalline (i-QC) particles endowed with high thermal stability. These values are notably higher than those achieved for A319, 6061-T6 and Al-8%wt.Cu–Mg–Ag cast alloys – three of the most common heat-resistant Al alloys, and higher than commercially available Al-based alloys for LPBF. Based on hardness measurements and the bimodal composite microstructure, we propose a model to predict this alloy's yield strength. This model shows a good agreement with the experimental results and can be used to maximize the alloy's tensile strength. This work describes a lightweight aluminum alloy with outstanding high temperature tensile strength within a wide range of temperatures, in addition to being additively processable and affordable.

Investigation of deformation comprised microstructure and precipitation of Cu–Sn–Ti alloy during hot deformation

The hot deformation behavior of Cu–Sn–Ti–(Cr) alloys was studied using Gleeble-1500D thermo-mechanical simulator ranging from 550 to 950 °C, and the strain rate was 0.001–10 s−1. The microstructure evolution of the alloy was analyzed using characterization methods such as electron backscatter diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Cu–Sn–Ti–(Cr) alloys were calculated by establishing the constitutive equation of the alloy. The activation energies of Cu–Sn–Ti and Cu–Sn–Ti–Cr alloys are 275.884 and 283.550 kJ/mol, respectively. The results indicate that the addition of Cr element has an inhibitory effect on the nucleation and improve refinement of dynamic recrystallization (DRX) in Cu–Sn–Ti alloy. The texture of Cu–Sn–Ti alloy is Cu texture at 750 °C and the texture contained in Cu–Sn–Ti alloy is Goss texture, Cubic texture and Cu texture when the temperature is raised to 950 °C. The texture of Cu–Sn–Ti–Cr alloy at 750 °C is Goss texture. The Goss texture transforms into Cubic texture and Cu texture when the temperature is raised to 950 °C. The precipitates present in Cu–Sn–Ti alloy include CuSn3Ti5 phase and Cu4Ti phase. The addition of Cr element adds a new phase of Cr to the alloy and also makes the distribution of precipitates more uniform and increases in quantity.

Ce effects on dynamic recrystallization and microstructure of the copper alloy under hot deformation behavior with different strain rate

The Cu–Ni–Sn–Ti–Cr and Cu–Ni–Sn–Ti–Cr–Ce alloys were compressed at 500–900 °C with 0.001–10 s−1 strain rates using the Gleeble 1500 deformation simulator. The effects of Ce addition on the microstructure and recrystallized grains of Cu–Ni–Sn–Ti–Cr alloy were investigated using EBSD and TEM. A constitutive equation was established to calculate the activation energy for the alloy hot deformation, and the optimal processing parameters were obtained. The corresponding texture of the Cu–Ni–Sn–Ti–Cr–Ce alloy deformed at 800 °C with 0.01 s−1, 0.1 s−1 and 1 s−1 strain rates is the {112}<100> Copper, {001}<111> Cubic and {011}<100> Goss texture. The texture of the Cu–Ni–Sn–Ti–Cr alloy deformed at 800 °C and 0.1 s−1 strain rate is the {011}<100> Goss texture. The strain rate and Ce addition can change the alloy texture. The precipitation phase in Cu–Ni–Sn–Ti–Cr (-Ce) alloy is mainly CuNi2Ti phase, and the addition of Ce can promote the precipitation of fine nanoscale precipitation phase in the alloy. Moreover, the addition of Ce can promote the dynamic recrystallization of the alloy, but the dynamic recrystallization of the alloy is suppressed with the increase of the hot deformation rate at the heat deformation temperature of 800 °C.

Machine-Learning-Based Composition Analysis of the Stability of V–Cr–Ti Alloys

Machine learning methods allow the prediction of material properties, potentially using only the elemental composition of a molecule or compound, without the knowledge of molecular or crystalline structures. Herein, a composition-based machine learning prediction of the material properties of V–Cr–Ti alloys is demonstrated. Our machine-learning-based prediction of the stability of the V–Cr–Ti alloys is qualitatively consistent with the composition-dependent experimental data of the ductile–brittle transition temperature and swelling. Furthermore, our computational results suggest the existence of a composition region, Cr+Ti ~ 60 wt.%, at a significantly low ductile–brittle transition temperature. This outcome contrasts with a reportedly low Cr+Ti content of less than 10 wt.% in conventional V–Cr–Ti alloys. Machine-learning-based numerical stability prediction is useful for the design and analysis of metal alloys, particularly for multicomponent alloys such as high-entropy alloys, to develop materials for nuclear fusion reactors.

Microstructure Formation and Mechanical Properties of Metastable Titanium-Based Gradient Coating Fabricated via Intense Pulse Ion Beam Melt Mixing.

The unique flash heating characteristics of intense pulsed ion beams (IPIB) offer potential advantages to fabricate high-performance coatings with non-equilibrium structures. In this study, titanium-chromium (Ti-Cr) alloy coatings are prepared through magnetron sputtering and successive IPIB irradiation, and the feasibility of IPIB melt mixing (IPIBMM) for a film-substrate system is verified via finite elements analysis. The experimental results reveal that the melting depth is 1.15 μm under IPIB irradiation, which is in close agreement with the calculation value (1.18 μm). The film and substrate form a Ti-Cr alloy coating by IPIBMM. The coating has a continuous gradient composition distribution, metallurgically bonding on the Ti substrate via IPIBMM. Increasing the IPIB pulse number leads to more complete element mixing and the elimination of surface cracks and craters. Additionally, the IPIB irradiation induces the formation of supersaturated solid solutions, lattice transition, and preferred orientation change, contributing to an increase in hardness and a decrease in elastic modulus with continuous irradiation. Notably, the coating treated with 20 pulses demonstrates a remarkable hardness (4.8 GPa), more than twice that of pure Ti, and a lower elastic modulus (100.3 GPa), 20% less than that of pure Ti. The analysis of the load-displacement curves and H-E ratios indicates that the Ti-Cr alloy coated samples exhibit better plasticity and wear resistance compared to pure Ti. Specifically, the coating formed after 20 pulses exhibits exceptional wear resistance, as demonstrated by its H3/E2 value being 14 times higher than that of pure Ti. This development provides an efficient and eco-friendly method for designing robust-adhesion coatings with specific structures, which can be extended to various bi- or multi-element material systems.

Influence of the Annealing Temperature on the Grain Structure of V–4Ti–4Cr Alloy after Thermomechanical Treatment with Rolling

Influence of the Annealing Temperature on the Grain Structure of V–4Ti–4Cr Alloy after Thermomechanical Treatment with Rolling

Shape memory effect and aging behavior of Bi-added Ti–Cr alloys for biomedical applications

For the further development of biocompatible metastable β (bcc) Ti alloys, the purpose of this study is to evaluate the potential of bismuth (Bi) addition in terms of shape memory properties and phase stability. It was found that the shape memory effect appeared in Ti–5Cr–1.6Bi (mol%) alloy. However, permanent (unrecoverable) deformation due to dislocations or twinning was also introduced simultaneously from the early stage of deformation. Regarding the formation of isothermal ω phase and the resulting hardness change by aging, it was found that the hardness change was large and that the isothermal ω phase formed in Ti–5Cr–1.6Bi alloy, while age hardening was small and no isothermal ω phase formed in Ti–5Cr–6.1Bi alloy. These results indicate the suppression of not only athermal ω but also isothermal ω phase by Bi addition. However, considering the fact that the alloy becomes brittle when Bi addition is over 3 mol%, it can be concluded that 1–3 mol% Bi addition is worth for the improvement of shape memory effect, suppression of ω phase, X-ray imaging, magnetic resonance imaging, and biocompatibility in metastable β Ti alloys.

Improved microstructure, mechanical properties and electrical conductivity of the Cu–Ni–Sn–Ti–Cr alloy due to Ce micro-addition

In this paper, new Cu–Ni–Sn–Ti–Cr and Cu–Ni–Sn–Ti–Cr–Ce alloys were prepared and studied. After solution treatment and 60% cold rolling, the Cu–Ni–Sn–Ti–Cr alloy with micro-hardness of 221 HV, a tensile strength of 598.1 MPa, elongation of 9.9% and electrical conductivity of 45.2% IACS was obtained after aging at 500 °C for 60 min. Furthermore, the new Cu–Ni–Sn–Ti–Cr–Ce alloy was also obtained using aging at 500 °C for 60 min, having 245 HV micro-hardness, 645.2 MPa tensile strength, elongation 9.4% and 44.6% IACS conductivity. The comprehensive properties of high strength, hardness, and electrical conductivity of the alloy are attributed to the composite effects of solution, deformation, grain boundary, and precipitation strengthening. Among them, precipitation strengthening plays a major role, and the precipitates are mainly nanometer CuNi2Ti, Cr, and NiTi phases. The interface between the nanometer CuNi2Ti phase and Cu matrix is a coherent, which can improve the strength of the alloy without sacrificing plasticity. In addition, texture type transformation and texture strength change of the alloy are closely related to the increase of micro-hardness. The micro-addition of trace rare earth Ce can refine the alloy grains, and promote dynamic recrystallization to produce finer grains, significantly improving the alloy’s micro-hardness.

Fabrication and mechanical properties of Bi-added Ti–Cr alloys for biomedical applications

The potential of the Bismuth (Bi) addition was evaluated for the development of biocompatible metastable β (bcc) Ti alloys from the viewpoints of mechanical properties and phase stability. The basic alloy was Ti–5 mol% Cr, and 0–9 mol% Bi was added in nominal composition. A Ti–Bi binary alloy was also selected. The alloys were fabricated using a standard laboratory-scale arc melting machine under an Ar atmosphere. The weight loss was significant during melting due to Bi evaporation. The measured Bi content is linearly proportional to the Bi nominal composition with MCBi = 2/3 NCBi, allowing the prediction and control of Bi content of the alloy. Then, the microstructure, workability, and mechanical properties were systematically investigated. The phase constitution of the Ti–5Cr binary alloy was β + α′ (hcp) + ω (hexagonal). The presence of the athermal ω phase resulted in significantly poor cold workability and poor ductility. It was also found that the addition of Bi to the Ti–5Cr alloy stabilized the β phase and suppressed the ω phase formation. The phase stability of Ti–Cr–Bi alloy is discussed using Mo equivalent and electron-to-atom (e/a) ratio. Ti–5Cr–1.6Bi alloy showed improved workability and ductility. However, with further increasing Bi addition, the Ti–5Cr–3.7Bi alloy showed no plastic deformation, and the Ti–5Cr–6.1Bi alloy was broken even during hot-rolling. Thus, it is concluded that ∼2 mol% Bi addition is suitable and that such a small amount of Bi addition is an attractive candidate for the development of β Ti alloys.

Preparation of layered gradient Cu–Cr–Ti alloy with excellent mechanical properties, thermal stability, and electrical conductivity

Abstract Cu–Cr–Ti alloy with gradient properties was prepared at 960°C for 2 h in air, 80% cold rolling, and then aging at 500°C for 1 h. The results showed that the surface layer of Cu–Cr–Ti alloy had achieved a good match of electrical conductivity (96.2% International Annealed Copper Standard (IACS)), thermal stability (softening temperature of 650°C), and wear resistance (friction coefficient of 0.17). Meanwhile, the core region maintains high tensile strength (519 MPa) and good electrical conductivity of 71.8% IACS. Transmission electron microscope characterization revealed that the precipitates of surface layer are composed of Cr oxides, complex oxides formed by Cu, Cr, and O, and Ti-rich phases. The existence of oxide particles with discontinuous distribution and stable properties is the reason for the good electrical conductivity, excellent thermal stability, and outstanding wear resistance of the surface layer. The main precipitates of the core are Cr. The high tensile strength of the core is ascribed to the aging strengthening effect of these fine Cr particles. This work provides ideas and approaches for the preparation of copper alloy with excellent properties for high-speed railway contact wire, and solves the drawbacks of composites synthesized from heterogeneous materials.

Formation and Growth of Grain Boundary (αTi) Layers and Their Hardness in Ti–Cr Alloys

Formation and Growth of Grain Boundary (αTi) Layers and Their Hardness in Ti–Cr Alloys

TiCr transition layer promoting the growth of high-stability TiCrN coating for titanium bipolar plate

High chemical stability under the harsh acidic working condition of proton exchange membrane fuel cell (PEMFC) is of great importance for bipolar plates. In present study, a series of TiCr alloys from amorphous to nanocrystalline state are designed as transition layers to promote the growth of smooth and dense TiCrN surface layer as coating material for Ti bipolar plate. Under the accelerated corrosion environment of PEMFC (0.5 M H2SO4 + 2 ppm HF, 80 °C with air, 0.2 V vs. Hg/Hg2SO4), the double-layer TiCr/TiCrN coating exhibits excellent long-term stability. A low current density of 0.25 μA/cm2 and a small interfacial contact resistance (ICR) of 6.5 mΩ cm2 are observed after 100 h corrosion test for the double-layer TiCr/TiCrN, which are much lower than the values of 1.35 μA/cm2 and 13.5 mΩ cm2 for single-layer TiCrN after 70 h corrosion test. These results indicate the high potential of double-layer TiCr/TiCrN as the coating material for Ti bipolar plate.

Comparison of two-body abrasive wear resistance of high chromium boron-containing Fe–C B–13wt.%Cr Ti alloy with incomplete replacement of Cr for Cu the Fe C B 4wt.%Cr 7wt.%Cu–Ti alloy

Hardfacing process commonly employed because of its low cost and high efficiency. The microstructure of an two sample of deposited metal by X-ray diffraction, scanning electron microscope (SEM). In this research, the mechanical and tribological properties of two deposited metal of Fe–C–Cr–B–Ti alloying systems, high chromium 140Cr13Si1MnBTi alloy, and low chromium and high copper 110Cr4Cu7TiVBAl alloy hradfecing by flux-cored arc welding process (FCAW) was studied. It provided a low content of chromium (4 wt.%) and a high content of copper (7 wt.% Cu). Results of the studies had showed that the introduction of exothermic addition (CuO‒Al) to the core filler of the flux‒cored wire electrode, change melting characteristic and provides the highest resistance of the deposited metal to abrasion wear due to additional alloying by copper and reduction in grain size.

Superior anti-impurity gas poisoning ability and hydrogen storage properties of Ti–Cr alloy by introducing zirconium as additive

In this work, the anti-impurity gas poisoning ability and hydrogen storage properties of Ti–Cr alloy by introducing zirconium as additive have been investigated. The results showed that all alloys had C14-type main phase and Ti minor phase. The lattice parameter a, c and cell volume of the C14-type phase rose as Zr content increased. Furthermore, after introducing Zr, all alloys could absorb hydrogen immediately without any prior heat treatment or hydrogen exposure with/without prolonged air exposure. The maximum hydrogen storage capacity and the average effective hydrogen storage capacity of TiCr2 alloy also increased with Zr content. The cycle properties of all alloys with/without prolonged air exposure were also discussed. The results showed that all alloys had good cycle stability even if the alloys were exposed to the air for 2 days. The above results suggested that the addition of Zr had a positive effect on improving the hydrogen storage properties and anti-impurity gas poisoning properties of TiCr2 alloy. Finally, the mechanisms of first hydrogenation kinetic of all alloys with/without prolonged air exposure were also investigated by using the rate limiting step.