Ti Cr Research Articles

Strategic lattice manipulation in transition metal nitrides for improved solubility

In this study, we propose a new concept for achieving metastable ternary transition metal nitride solid solutions, focusing on face centered cubic (fcc) structured Ti(N,B) as a model system. Combining non-reactive magnetron sputtering with computational analysis, we develop a microalloying strategy to manipulate the metallic sublattice, thereby influencing the solubility of B in the non-metal sublattice. We show that imposed tensile strain on the fcc-TiN lattice facilitates the solubility of B, with a 1.5 % strain enabling the incorporation of ∼28.5 at.% B at the non-metal sublattice. Conversely, compressive strain hinders the formation of the fcc-Ti(N,B) solid solution, highlighting the importance of lattice manipulation in controlling solubility. At the same time, our experimental findings reveal that adding larger atoms, such as Zr, to the metal sublattice enhances the solubility of B in fcc-TiN more effectively (∼2 at.% Zr proves to be sufficient to solute 10 at.% B in the fcc-TiN lattice) than smaller atoms, like Cr or similar-sized Ti atoms. The size effect of the alloying atoms on the B solubility is further supported by radial distribution function analysis, showing lower local lattice distortions for Zr compared to Cr.

High-throughput determination of interdiffusivity and atomic mobilities in bcc Ti–Cr–Mo alloys

A comprehensive understanding of the diffusion coefficients and atomic mobilities in the Ti–Cr–Mo system is crucial for establishing an atomic mobility database for titanium-based high-strength titanium alloys. In the present work, nine sets of solid/solid diffusion couples were prepared and measured in bcc Ti–Cr–Mo alloys, with the temperatures ranging from 1373 to 1473 K. Scanning electron microscopy (SEM), and Electro Probe Micro-Analysis (EPMA) techniques were used to respectively test its microstructure and composition distance. The diffusion coefficients in bcc Ti–Cr–Mo alloys were determined using the Matano-Kirkaldy method and numerical inverse method respectively. The diffusion coefficients obtained from the above two methods exhibit good consistency. The atomic mobility parameters for the Ti–Cr–Mo systems were provided with the assistance of HitDIC software. A three-dimensional plot of interdiffusivities was generated for chromium and molybdenum contents ranging from 0 to 20 mol % and 0–14 mol %. Moreover, the application of the Arrhenius equation enabled the determination of changes in frequency factors and activation energies concerning temperature and composition.

Effect of Trace Elements on the Thermal Stability and Electrical Conductivity of Pure Copper

Abstract: The impact of introducing trace transition elements on the thermal stability and conductivity of pure copper was examined through metallographic microscopy (OM), transmission electron microscopy (TEM), and electrical conductivity measurements; the interaction between trace transition element and trace impurity element S in the matrix was analyzed. The results show that the addition of trace Ti and trace Cr, Ni, and Ag elements significantly enhances the thermal stability of the pure copper grain size. After high-temperature treatment at 900 °C/30 min, the grain sizes of Cu, Cu-Ti-S, and Cu-Cr-Ni-Ag-S were measured and found to be 200.24 μm, 83.83 μm, and 31.08 μm, respectively, thus establishing a thermal stability ranking of Cu-Cr-Ni-Ag-S > Cu-Ti-S > Cu. Furthermore, the conductivities of pure copper remain high even after the addition of trace transition elements, with recorded values for Cu, Cu-Ti-S, and Cu-Cr-Ni-Ag-S of 100.7% IACS, 100.2% IACS, and 98.5% IACS, respectively. The enhancement of thermal stability is primarily attributed to the pinning effect of the TiS and CrS phases, as well as the solid solution dragging of Ni and Ag elements. Trace Ti and Cr elements can react with S impurities to form a hexagonal-structure TiS phase and monoclinic-structure CrS phase, which are non-coherent with the matrix. Notably, the CrS phase is smaller than the TiS phase. In addition, the precipitation of these compounds also reduces the scattering of free electrons by solute atoms, thereby minimizing their impact on the alloy’s conductivity.

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.

Evolution of structure, magnetism, and electronic/thermal-transports of Ti(Cr)-substituted Fe2CrV all-d-metal Heusler ferromagnets

All-d-metal full-Heusler alloys possess superior mechanical properties and high spin polarization, which would play an important role in spintronic applications. Despite this, their electrical and thermal transport properties have not been comprehensively investigated till now. In this work, we present an analysis on the evolution of structural, magnetic and transport properties of Cr- and Ti-substituted Fe2CrV all-d-metal Heusler alloys by combining theoretical calculations and experiments. Both series of alloys crystallize in Hg2CuTi-type structure. With increasing Ti doping, the calculated total magnetic moments of Fe50Cr25V25-xTix decrease linearly. The experimental saturation magnetization is highly consistent with theoretical calculations and Slater-Pauling rule when x < 4, indicating the highly ordered atomic occupation. The magnetization and Curie temperature can be significantly tuned by altering spin polarizations and exchange interactions. The introduction of the foreign atom, Ti, results in a linear increase in residual resistivity, while electron-phonon scattering keeps relatively constant. The maximum values for electrical and thermal transport properties are observed in the stoichiometric Fe2CrV composition.

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

Experimental and Theoretical Investigation on the Enhanced Hydrogen Storage Performance of Ti–Cr–Mn–Fe-Based Alloys Modified by Nb Substitution

Experimental and Theoretical Investigation on the Enhanced Hydrogen Storage Performance of Ti–Cr–Mn–Fe-Based Alloys Modified by Nb Substitution

Tribological Characteristics of Ti–Al– N, Ti–Al– Ni–N, Ti–Cr–Ni–N, and Ti–Cr–Ni–Mo–N Strengthening Coatings on Steel 20Kh13 in a Friction Pair with Carbon Fiber and Their Corrosion Resistance

Tribological Characteristics of Ti–Al– N, Ti–Al– Ni–N, Ti–Cr–Ni–N, and Ti–Cr–Ni–Mo–N Strengthening Coatings on Steel 20Kh13 in a Friction Pair with Carbon Fiber and Their Corrosion Resistance

High‐Precision Dilatometry for the Study of Precipitation Processes and Microalloying Effects in Lightweight Alloys ‐ A Specific Review

By dilatometry, the absolute change in the length of a sample is measured. As length, i.e., volume, is a state variable, its change can be monitored for long time ranges. This is the decisive advantage compared to the widely applied calorimetric methods which are based on a rate (change of heat) and where the maximum time range is determined by the resolution limit of the heat flow measurement. In contrast, if the measurement environment is kept at a constant temperature, dilatometric signals can be measured for very long time ranges down to very small changes with resolution in the nm range. The application of high‐stability isothermal dilatometry for studying precipitation phenomena in Al(Mg,Si)‐, Ti(V)‐, and Ti(Cr)‐alloys is summarized in the present review. Al(Mg,Si) turns out as a prime example where the various phases can unambiguously be distinguished by their characteristic length change features. For Ti(V), the influence of the oxygen impurity on the omega phase formation, and for Ti(Cr), the effect of Sn alloying on the omega phase formation can be revealed by dilatometry. The results on Al(Mg, Si) are compared with dilatometry on Al(Cu)‐alloys upon time‐linear heating, for which also the effect of microalloying with Au is studied.

Microstructural Map and Phase Chemical Compositions in Hybrid Multi-component Cast Alloys Fe–W–Mo–V–Cr–Ti–(1.5–3.5 Wt Pct)B–(0.3–1.1 Wt Pct)C

Microstructural Map and Phase Chemical Compositions in Hybrid Multi-component Cast Alloys Fe–W–Mo–V–Cr–Ti–(1.5–3.5 Wt Pct)B–(0.3–1.1 Wt Pct)C

Correction: Experimental Investigation and Thermodynamic Assessment of the Cr–Ti System

Correction: Experimental Investigation and Thermodynamic Assessment of the Cr–Ti System

Ti–Cr–N Nanopyramid/Nitrogen-Doped Carbon Quantum Dot/Stainless Steel Mesh as a Flexible Supercapacitor Electrode

Ti–Cr–N Nanopyramid/Nitrogen-Doped Carbon Quantum Dot/Stainless Steel Mesh as a Flexible Supercapacitor Electrode

Strength of Disordered and Ordered Al‐Containing Refractory High‐Entropy Alloys

Body‐centered‐cubic refractory high‐entropy alloys are promising for high‐temperature structural applications due to their exceptional properties, particularly in terms of yield strength at elevated temperatures. For certain alloy systems, such as Mo–Ti–Cr–Al, both disordered (A2) and ordered (B2) crystal structures are possible. In this particular system, a solid‐state transformation from A2 to B2 during cooling occurs. For Al concentrations above ≈10 at%, B2 order is obtained from the transformation temperature down to room temperature (RT), while A2 is stable above RT below the critical Al content. Herein, two alloys from the Mo–Ti–Cr–Al system close to the transition between A2 and B2 are investigated. Nanoindentation tests reveal that the magnitude of strain rate sensitivity for both alloys is small compared to classical alloys, however, significantly temperature dependent up to the strength plateau temperatures. The yield strength plateau, which is insensitive to the strain rate, is observed at temperatures exceeding 573 K. Modeling of solid solution strengthening reproduces the experimental data in the Al‐lean A2 alloys. However, the observed discontinuous increase of strength in the Al‐rich B2 alloys can only be rationalized by the appearance of B2 order and to no significant other obvious strengthening mechanisms.

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 %).

High-temperature oxidation behavior of a 9Cr oxide dispersion strengthened alloy under limited oxygen condition

Hot compression bonding is a promising process to fabricate large-scale oxide dispersion strengthened alloys. Inevitable interface oxidation could affect the effectiveness of the joint. The high-temperature oxidation behavior of a 9Cr ODS alloy under limited oxygen condition was investigated. The oxidized surface consisted of inner Fe2O3 scale and outer Cr2O3 particles at 800 °C. Reoxidation at 1000 °C, Cr2O3 particles were decomposed and converted into Cr(Ti)O2. With increasing oxidation time, Fe2O3 and Cr(Ti)O2 were decomposed and Y2O3 pegs formed. Furthermore, TiO2, Y2O3 and Y-Ti-O nanoparticles formed along grain boundaries. In conclusion, the oxide evolution could be summarized as Fe2O3→Cr2O3→Cr(Ti)O2→TiO2→Y2O3→Y-Ti-O nanoparticles. The evolution from initial coarse Cr-rich and Fe-rich oxides to fine Y-Ti-O nanoparticles is expected to be critical for hot compression bonding processes.

Application of modern fractal formalism methods for researching the influence of ion-plasma coatings on assessing the wear resistance of volume hydraulic drive components

Problem. The studies on preparation and application of Ti–Cr–N coating on the surface of the 38Х2МЮА steel have been conducted. Goal. The purpose of the work is to investigate the feasibility of using a fractal approach to evaluate the effect of plasma coatings to increase the wear resistance of parts of a volumetric hydraulic drive. Methodology. Cr was chosen as the material for ion bombardment, since it makes it possible to reduce the temperature of the substrate before applying ­the coating and avoid the risk of surface softening. After heat treatment of the 38Х2МЮА steel, its hardness ranges from 40 to 45 HRC. The thickness of the applied coating varied from 3 to 6 microns, which corresponds to good adhesion, a smaller thickness does not significantly affect the properties of the product, and in the case of a thickness of more than 6 microns, peeling is observed due to poor adhesion to the substrate. Results. Five series of experiments with HRC hardness values of 42, 43, 44, 45, 46 were performed. Fractal analysis was used to assess the effect of the Ti–Cr–N coating structure of the working surface of volumetric hydraulic drive parts on its wear indicators. The relative error in calculating wear indicators for fractal models ranged from 0.04 to 8.96. The correlation coefficient of Y(X2) model without using indicators of the surface fractal dimension was only 0.73. Experiments proved that the lowest wear value of 2.11 g*10-3 was obtained at a coating thickness of 6 µm and hardness of 45 HRC. At the same time, a roughness coefficient was 0.16. To confirm this hypothesis, an experiment to determine wear resistance at a hardness of 45, roughness of 0.16, and coating thickness of 6 was conducted. Conclusions. Results of the studies of wear indicators of Ti–Cr–N coated samples at the substrate material hardness values from 42 to 46 HRC, surface roughness and coating thickness showed feasibility of the fractal structure estimation approach.

Stoichiometry and annealing condition on hydrogen capacity of TiCr2-x AB2 alloys

This study presents the effect of stoichiometry and annealing condition on Ti–Cr AB2-type hydrogen storage alloys. Prior to annealing the majority phase of the as-cast alloys was the C14 Laves phase, with separate Ti and Cr phases. Annealing treatment (1273 K/14 d) led to a transition from C14 to C15 Laves phase structure. Both C14 (as-cast) and C15 (annealed) cell size increased with Ti content, up to a ratio (Cr/Ti) of 1.6, due to B-site Ti substitution in the lattice up to a limit. Pressure composition isotherm (PCI) measurements demonstrated alloys containing a greater Ti content had a better maximum hydrogen storage capacity (1.5 vs. 1.03 wt%) and lower plateau pressure (9.4 vs. 15.8 bar) at 253 K. Annealing resulted in a lower storage capacity (1.05 vs. 1.49 wt%), greater plateau pressure (ca. 30 bar) and flatter plateau slope (25 % reduction in plateau slope). Reduction in hydrogen storage capacity of annealed alloys could be due to diffusion of residual Cr in the alloy into the C15 Laves phase during the annealing process, thereby changing the local composition as confirmed through X-ray diffraction (XRD).

A novel low-cost Ti–Cr–Fe β-Ti alloy with TWIP effect: Sensitivity of tensile properties to microstructural characteristics

A novel low-cost Ti-4.6Cr–3Fe β-Ti alloy with twining induced plasticity effect was designed, and its tensile properties and deformation mechanisms were sensitive to its microstructural characteristic. The received sample with the microstructure of β matrix embedded isothermal ω (ωiso) precipitations exhibited the largest tensile strength (Rm), but the limited ductility (<3 %). When the solution treatment (ST) temperature increased from below to above α→β transition temperature, the microstructure changed from β matrix with αs precipitations to β matrix with athermal ω (ωath) precipitations, and the deformation mechanisms correspondingly changed from dislocation slip to the combination of dislocation slip and {332} deformation twins. Among different treatment samples, the ST800 sample obtained a relatively good combination of Rm (1146 MPa) and elongation to failure (EL, 12.5 %). It is surprising that, as the ST temperature increased from 800 °C to 900 °C, the Rm increased from 1146 MPa to 1230 MPa, but the fracture mode changes from ductile fracture to brittle fracture due to the formation of Laves phase (TiFe2) at grain boundaries. These findings provide a basis for improving the tensile properties of Ti-4.6Cr–3Fe alloy by adjusting the microstructure, and a reference for optimizing the composition of Ti–Cr–Fe system low cost β-Ti alloys.

Ten-Year Recycling of Vanadium Alloy in Fusion Reactors

Low-activation characteristics and dominant radioactive isotopes limiting materials recycling were analyzed for a fusion-reactor-grade vanadium alloy, NIFS-HEAT-2. In order to reduce contact dose rate after use in fusion reactors, purification of the base metal vanadium was examined by chemical aqueous separation, electron-beam vacuum melting and zone refining, focusing on the removal of the dominant high-activation impurities, such as Co, Cu, Fe, Nb, Ni and Mo. Based on the measured impurity levels, remote recycling of vanadium alloy is possible within ten years after use in fusion reactors under operation condition with 100 dpa irradiation. Early quasi-hands-on recycling requires further purification and re-design of alloy composition especially with low Ti and high Cr content. The present paper discusses status of material R&amp;Ds for the ten-year recycling and impact on operation of fusion reactors.

Improved hydrogen ab-/desorption performance of Ti–Cr based alloys via dual-effect of oxide reduction and element substitution by minor Al additive

Hysteresis of hydrogen storage alloys essentially hinders the compressibility and operation efficiency of metal hydride hydrogen compressors. In this work, minor Al additive was added into Ti–Cr based hydrogen compression alloys through induction levitation melting, and the apparent hysteresis was successfully ameliorated. The XRD and SEM results indicate homogeneous element distribution of a main C14 Laves phase of Ti0.96Zr0.06Cr1.0Mn0.6Fe0.4Alx (x = 0, 0.01, 0.02, 0.04, 0.08) alloys, and vanishing of a minor oxide phase in case the Al additive is introduced. As Al stoichiometry increases in the alloys, the hydrogenation plateau decreases obviously but the dehydrogenation plateau hardly changes. Meanwhile, the hydrogen capacity ascends initially but descends slightly. Additionally, no severe performance degradation is induced. The mechanism for overall performance improvement can be concluded as dual functions of Al additive: one can be oxide reduction of other elements during melting determined by XPS and ICP, and the other can be partial Al substitution for the B-side elements, leading to relieved deformation energy surrounding the vacant Al-containing interstitials. As to hydrogenation kinetics, the alloys exhibit accelerated hydrogenation rate with increased Al stoichiometry due to decreased activation energy and hydrogenation plateau. Furthermore, the first-principles calculation results indicate random Al substitution for the B-side atoms, and anisotropic expansion of the unit cell can be attributed to Al substitution at 6h sites. This work reveals a simple and effective way to enhance hydrogen storage performance of Ti–Cr based alloys.