Ti Cr Research Articles

Low activation V–Fe–Cr–Mn high-entropy alloys with exceptional strength

V-based alloys such as V–4Cr–4Ti are one of the most promising candidate materials for fusion energy demonstration reactors, owing to their low activation and excellent resistance to neutron irradiation. However, conventional V-based alloys have poor high-temperature strength and creep resistance, resulting in a limited operating temperature window (400–700 °C). In this study, a series of low-activation VxFe65-xCr15Mn20 high-entropy alloys (HEAs) are designed and prepared by arc melting. Increasing the content of V of HEAs increases their nucleation rate during solidification, and thus decreases their grain size and increases their microhardness and strength. The yield strength of V50Fe15Cr15Mn20 HEA reaches 1189 MPa, which is mainly caused by the reduced grain size. The yield strength of V50Fe15Cr15Mn20 HEA between room temperature and 1000 °C is significantly higher than that of conventional V-based alloys. Such high high-temperature strength is explained by the high microstructural stability of the designed HEA. As a novel nuclear material, the present V50Fe15Cr15Mn20 HEA tested at a temperature of 900 °C still has a yield strength of 275 MPa, which is higher than that of conventional low-activation steels and V-based alloys.

Effect of cold work deformationon irradiation hardening of vanadium alloys

Vanadium alloys are regarded as promising candidate structural materials for the advanced blanket concept in fusion reactors due to their low activation, good high-temperature strength and, in particular, their compatibility with liquid lithium. In the present work, six kinds of V–5Cr–5Ti alloys under heavy cold work with deformation amounts of 40%, 60% and 80%, and/or subsequent annealing were investigated. Irradiation damage of 0.1, 0.3 and 0.5 dpa was introduced in both specimens using 352.8 MeV Fe ions at 100 °C. Electron backscattered diffraction and transmission electron microscopy (TEM) were used to investigate pre-irradiation microstructures such as grains, dislocations, precipitates and bubbles. X-ray diffraction was used to evaluate the pre-existing dislocation density and TEM was used to image the irradiation defects. The change in hardness was evaluated using micro-hardness tests. Before irradiation, the hardness increased with the increasing deformation amount but decreased after subsequent annealing. Dislocation cells turning into sub-grains with low-angle boundaries were observed, while the deformation amount reached 80% in cold-worked specimens. After irradiation, hardening was observed in all specimens and at all irradiation doses, and a power-law relation was observed in dose-dependent hardening. The effect of the initial microstructure on irradiation hardening was discussed in terms of the sink strength while ignoring grains and precipitates due to their large size. Pre-existing bubbles could effectively reduce irradiation hardening compared with previous results. Meanwhile, with the increasing sink strength of dislocations, hardening decreased in a different manner in cold-worked and annealed specimens. The irradiation defects in some specimens were investigated to clarify the inherent mechanism in the relationship between the initial microstructures and irradiation hardening.

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.

Cr-Ti Mixed Oxide Molecular Cages: Synthesis, Structure, Photoresponse, and Photocatalytic Properties.

The solvothermal reaction of titanium isopropoxide and chromate in the presence of benzoate produced two novel host-guest clusters encapsulating Cs+ or H3O+, (H3O)@Ti7Cr14 and Cs@Ti7Cr14. The most remarkable feature is that the Ti7O7 ring is concentrically embraced by a Cr14O14 ring to form a rigid Ti7Cr14 host. ESI-MS and 133Cs NMR revealed that the overall framework structures are preserved, whereas the benzoate ligands on the two clusters may be labile in solutions. Both (H3O)@Ti7Cr14 and Cs@Ti7Cr14 exhibit good UV-vis light-responsive properties and photocatalytic activities, with absorption edges extending up to 780 nm. Cs@Ti7Cr14 is an effective visible-light-responsive photocatalyst in both the heterogeneous methylene dye degradation and homogeneous CO2 cycloaddition reaction under mild conditions like room temperature and 1 bar of CO2. According to the mechanism studies, Cs+, as a rigid guest, can significantly improve the photogenerated charge separation efficiency of the Ti7Cr14 host, thereby improving its interface charge separation properties, photocurrent, and photocatalytic activities. Our findings not only provide new members of heterometallic titanium oxide clusters to enrich the metal oxide cluster family but also open up new possibilities for their photoresponses, which may play an important role in solar energy harvesting for sustainable chemistry.

Predicting hydrogen storage capacity of V–Ti–Cr–Fe alloy via ensemble machine learning

The V–Ti–Cr–Fe quaternary alloy is a promising hydrogen storage material for excellent performances, but it is difficult to take reliable multi-factor synergistic effects into account by means of experiments. At present, using the data-driven innovation method of ensemble learning, the structure-property relationship of V–Ti–Cr–Fe alloy is built and the maximum hydrogen absorption capacity is accurately predicted as well through 19 features covering the composition and various crystal parameters with the mean square error of 0.187. The feature importance ranking indicates that valence electron concentration, lattice constant, and Z/r3 play a critical role in the prediction. The genetic algorithm is furtherly used to propose 3 optimal composition ranges, which are proved to be accurate by experiments with relative errors of around 1%. The present work could provide an effective way for accurate and rapid prediction of hydrogen storage capacity and rational design of high-performance alloys.

Microstructure and properties of a Ni–Ti–Cr–Mo–Nb alloy fabricated in situ by dual-wire arc additive manufacturing

A Ni–Ti–Cr–Mo–Nb wall component was fabricated for the first time by dual-wire arc additive manufacturing (in situ alloying) using TA1 and Inconel 625 welding wires as feedstock for the potential application in fields characterized by low temperature environments, such as polar research and space exploration. The microstructure and properties of the as-built component were studied. The results show the as-built component consists of NiTi (B2), Cr2Ti, and Ti2Ni phases. In the upper region, Ti2Ni phase is present as nanoparticles mainly embedded in Cr2Ti phase. Cr2Ti phase is present as long oriented strips or granular precipitates. Due to the presence of secondary Cr2Ti and Ti2Ni phases, the hardness of this component is 600–650 HV0.2. The average compression strength is ∼1970 MPa and it exhibits outstanding superelasticity with a recoverable strain of 5.5%. The austenite finish temperature is −62 °C, which indicates that Ni–Ti–Cr–Mo–Nb alloy has the superelasticity at low temperature.

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.

Development of a technology for magnetron sputtering of composite nanostructured coatings from an alloy of the V–Ti–Cr–TiC system

The results of the study of alloys of the V–Ti–Cr–TiC system for obtaining composite nanostructured coatings using the magnetron sputtering are presented. The studied coating has a high level of microhardness and wear resistance.

Effect of chromium–titanium on corrosion and erosion of HVOF coating

ABSTRACT The high-velocity oxyfuel spraying (HVOF) method was used to coat Fe–Cr–Ti-based coating material Fe60Mo5C15Si10Cr0Ti10, Fe50Mo5C15Si10Cr10Ti10, Fe50Mo5C15Si10Cr10Ti0 on base material 316L stainless steel. A comparative analysis was performed to investigate the effect of alloying element chromium and titanium on corrosion and erosion properties of Fe–Cr–Ti coating material. NaCl solution (3.5 wt.) was used for the study of corrosion behaviour. The steady-state erosion wear was examined by varying parameters such as impact speed and impact angle. It was found that the micro-hardness and fracture toughness of Fe–Cr–Ti coating material with 10 wt-% titanium were 18.02 and 5.08% more than those of the coating material with 10 wt-% chromium, respectively. This showed that titanium played a more significant role than chromium in terms of mechanical and erosion properties and a less significant role in terms of corrosion behaviour. Fe50Mo5C15Si10Cr10Ti10 indicated the least wear and a smooth surface with very few pores and wear scars.

THE EFFECT OF ULTRA-FINE ALLOYING ELEMENTS ON THE PHASE COMPOSITION, MICROSTRUCTURE, HIGH-TEMPERATURE STRENGTH AND FRACTURE TOUGHNESS OF Ti–Si–X AND Ti–Cr–X COMPOSITES

Advanced Ti-based composites are promising for applications in components of modern aircraft and rocket engines as well as other power equipment owing to their high strength-to-weight ratio and fracture toughness in a temperature range of 20 °C to 650 °C. However, there is a need to increase their operating temperature range up to 700−800 °C. In this work, mechanical behavior of Ti–Si–X composites (X=Al and/or Zr, Sn, C) has been studied. For comparison, mechanical behavior of Ti–Cr–X composite (X=Al and/or C) has been studied. As-cast and thermo-mechanically deformed series of beam specimens were examined. Strength tests of specimens were performed under three-point bending in a temperature range of 20 °C to 1000 °C. Single-edge notch beam (SENB) tests under three-point bending of specimen series were carried out in a temperature range of 20 °C to 900 °C for estimating fracture toughness of materials. Based on the constructed dependences of fracture toughness and strength on testing temperature for the specimen series as well as the microstructure and failure micromechanism analyses, the role of ultra-fine alloying elements in achieving good high-temperature strength and fracture toughness of the studied composites was substantiated.

Strengthening caused by precipitates with different morphologies in Cu–Cr–Ti alloys: The role of dislocation bending angle

Addition of a small amount of Ti can significantly improve strength of Cu–Cr alloys. Previous work found that addition of Ti produced both spherical and cubic-shaped Cr particles. In this work, the hindering effect of Cr particles with different morphologies on dislocation was further studied. Transmission electron microscopy and high-resolution transmission electron microscopy were used to observe the bending angle of dislocations cutting through precipitated phase particles at about 108° or 54°. The angle of dislocations cutting through the spherical particles was 108° and that of the cubic particles was 54°. Theoretical calculations of dislocation bending angle to enhance strength determined that the bending angle of dislocations cutting cubic particles is about 54°. This study provides new insights for the design and preparation of high-strength and high-conductivity copper alloys.

Improved hydrogen storage properties of Ti2CrV alloy by Mo substitutional doping

Controllable hydrogen release is of great importance to the practical application of hydrogen storage materials. Ti 2 CrV alloy possesses the maximum hydrogen absorption capacity in the Ti–Cr–V series alloys, however, can hardly meet the reversible storage capacity of practical applications due to its stable dihydride. Here we report an advancement in hydrogen storage property of the Ti 2 CrV alloy by Mo partial substitution for Ti. Although the hydrogen absorption kinetics slightly decreased with the increase of Mo content, the Mo substitution alloy achieves an effective hydrogen capacity of 2.23 wt% cutting-off at 0.1 MPa, much higher than Ti 2 CrV alloy (0.8 wt%). It is ascribed that Mo partial substitution for Ti significantly decreased the dihydride stability as well as the enthalpy change value. The cyclic property of Ti 2 CrV alloy drastically decreased, while Mo substitution alloy with smaller FWHM value can maintain 90% storage capacity after 20 cycles. Because lattice strain and distortion of the Ti 2 CrV alloy were decreased by Mo doping. • Mo doping significantly enhanced the effective hydrogen storage capacity of Ti 2 CrV alloy. • Mo doping decreased lattice parameters, FWHM values, and enthalpy change of Ti 2 CrV alloy. • Mo substitution improved the cyclic property of the alloy. • Kinetics and thermodynamics of Mo-doped alloy upon de-/hydrogenation were calculated.

Effect of temperature history on the irradiation behavior of vanadium alloy irradiated with the MARICO-II rig in a fast reactor, JOYO

The irradiation behavior of vanadium alloys was examined to evaluate the effect of temperature history during reactor operation. Irradiation experiments were performed in a fast reactor, Joyo, with an irradiation-temperature-controlled irradiation rig, MARICO-II. In-core irradiation rigs that control the irradiation temperature and are not influenced by reactor power were used. Irradiation conditions with or without the MARICO-II rig were performed. Significant differences in irradiation hardening and swelling behavior in undersized vanadium binary alloys were visible between temperature-controlled and conventional rigs. The temperature history affects the microstructural evolution, especially the nucleation and growth of voids during startup and shutdown procedures. No difference was observed in the vanadium alloys with oversized solute atom because the vacancy migration was suppressed by tight binding between oversized solute atoms and vacancies during irradiation. V–4Cr–4Ti–(Si,Al,Y) alloys showed significant irradiation hardening at high-temperature irradiation even though the contribution of dislocation and precipitates for irradiation hardening was insufficient to satisfy the measured irradiation hardening. The significant irradiation hardening in the V–4Cr–4Ti–(Si,Al,Y) alloys may be caused by transmission-electron-microscope-invisible clusters including minor elements (Si, Al, Y) that were formed at a high temperature during irradiation.

Reactive grid-assisted co-sputtering of titanium and chromium in a pure nitrogen atmosphere: Uniformity, optics, and structure of the Ti–Cr–N films

This study provides the results of the first attempt to deposit thin films by reactive grid-assisted co-sputtering with the deployment of small grounded grids having two varying apertures for enabling the transfer of particles. The diameter of all the grids utilized was 50 mm, and their apertures' diameters were changed from 5 mm to 15 mm. Furthermore, the ratios of the grid area to the chamber wall area were lower than 0.0161, preventing the formation of ion-rich sheaths and their adverse impact upon discharge and plasma stability. Accordingly, Ti 1 Cr 1-x N films (0.88 < x < 0.97) with low chromium contents were deposited on soda-lime glass substrates by using pure nitrogen as the sputtering gas. The grazing incidence X-ray diffraction patterns of the films, the average thicknesses of which were lower than 50 nm, showed no sign of crystallinity in the films. Ranging from 3.26 to 3.79 eV, the optical bandgap of the films changed by altering the apertures’ size; chromium content, internal stress, and quantum confinement effect appeared to be the main contributing factors. The photoluminescence intensities appertaining to trap state emissions reflected a decreasing trend by increasing the chromium content, which can be ascribed to the capability of the chromium particles included in the surface, structure, and grain boundaries of the films to prevent photoinduced electron-hole pairs from recombination. It was found that not only is the grid-assisted co-sputtering method an effective tool whereby the doping range of conventional co-sputtering methods can be significantly extended but also it can cover a spectrum of surface morphologies. However, in comparison with the conventional co-sputtering method, the utilization of the grids with fairly small apertures can limit the thickness uniformity of the films; this effect may be attenuated by changing the geometry and design of grids.

Processing and properties of yttria and lanthana dispersed ODS duplex stainless steels

In the present study, yttria (alloy B) and lanthana (alloy C) based oxide dispersion strengthened (ODS) duplex stainless steels (Fe–21Cr–8Ni–1Ti) have been synthesized using mechanical alloying followed by spark plasma sintering (SPS). For comparison, duplex steel without dispersion (alloy A) has also been synthesized. The variation of sintering temperature (900, 1000 and 1050 °C) on the density, microstructure, and mechanical properties of the steels have been reported. The austenite phase fraction increased with the sintering temperature as well as by the addition of oxides. TEM analysis confirmed the presence of nano-clusters (size in the range of 2–8 nm) of Y–Ti–Cr–O and La–Ti–Cr–O in the alloy B and alloy C, respectively. Alloy C, sintered at 1000 °C, exhibited the highest micro-hardness and compressive strength of 739 ± 9.1 HV and 2835 ± 87 MPa, respectively. At all sintering temperatures, the lower hardness values of the alloy B as compared to alloy A were ascribed to the significantly higher austenite phase fraction in the former, which resulted in overcoming the dispersion strengthening effect. Overall, La2O3-based ODS duplex stainless steels exhibited the better room temperature mechanical properties than Y2O3-based ODS steels.

Computational screening of spinel structure cathodes for Li-ion battery with low expansion and rapid ion kinetics

Lithium ion batteries (LIBs) dominate the market of energy storage systems due to their high energy density and light weight. Spinels, a group of environmentally friendly, low cost and thermal stable materials, have been reported as high-performance cathode candidates of LIBs. In spinel LIBs, Mn-based spinels (LiMnO4) have been widely studied, and further reports have been carried out on the doping of LiMnO4 structures to suppress the disproportionation reaction of the Mn3+. However, the application of spinel cathodes in LIBs is still affected by the volume expansions and slow ion diffusion kinetics. In this work, we generated 62 spinel materials from the periodic table based on the widely studied LiB2X4 and LiMn1.5B0.5X4 structures (i.e., Mn-based spinel with doping of elements B), where the element B can be chosen from the Co, Cr Fe Ir, Mn, Mo, Ni, Pd, Pr, Rh, Ti, V, Ce, Tb, Ru or Ta while the element X can be an anion of O or S. Based on the density functional theory (DFT), the electronic conductivities, expansion coefficients and ion kinetics of the selected 62 spinel structures were predicted. Finally, we screened out 18 structures having excellent electronic conductivity (i.e., the band gap, Eg = 0), low expansion coefficient (<10%) and low diffusion energy barrier (<0.4 eV). In addition, 8 spinel structures were found to be superionic conductor with extremely high ionic conductivity (>10−4 S·cm−1). The proposed work not only filtered out the spinel electrode materials with the best performance for LIBs and found the superionic conductor based on lithium spinel, but also provided an efficient solution for the search of other excellent electrode materials with optimal structures.

Microstructure and properties of the C/C-superalloy brazed joint by Ni-based filler

Stable and reliable C/C-superalloy joints that can withstand high-temperature service will become extremely important. Ni-based filler was employed for successful brazing of C/C composites and In738LC superalloy in this study. The brazed joints contained isothermal solidification zone (ISZ), diffusion affected zone (DAZ), and penetration zone close to the C/C side. The ISZ contained lots of carbide-borides besides Ni(s,s) and Cr(s,s). The specific composition and atomic arrangement of these phases were characterized by the focused ion beam (FIB) method and transmission electron microscopy (TEM) analysis. Results showed the obvious lattice distortion of the Ti–Mo–B compound indicated the presence of the severe internal residual stress. The microhardness distribution of the brazed joint was analyzed in combination with the microstructure. Brittle Cr–Ti–Mo carbide-borides formed in the reaction layer contributed to the high microhardness, and the shape of borides influenced the DAZ microhardness significantly When the brazing temperature was 1100 °C, the highest joint shear strength was obtained due to a matched proportion of the width and the microhardness of ISZ.

Effect of Hydrogen on Young’s Modulus and Internal Friction of V–4Ti–4Cr Alloy

Effect of Hydrogen on Young’s Modulus and Internal Friction of V–4Ti–4Cr Alloy

Effect of the Content of Polyvinyl Butyral on the Synthesis and Phase Composition of Products of Combustion of Ti–Cr–C Granular Mixtures

Effect of the Content of Polyvinyl Butyral on the Synthesis and Phase Composition of Products of Combustion of Ti–Cr–C Granular Mixtures

Evolution of microstructure and mechanical performance of plasma-sprayed Ti–Cr–Si–C coatings annealed at 800 °C and 1100 °C

In this work, Ti–Cr–Si–C coatings were plasma sprayed from Ti/Cr/Si/graphite powders and their microstructure evolution and mechanical properties after annealing at 800 °C and 1100 °C were studied. Ti–Cr–Si–C coatings were sprayed with a lamellar structure and they consisted of TiC, Ti5Si3, MAX-Ti3SiC2, Cr, unreacted Si and graphite. After annealing at 800 °C and 1100 °C, MAX-Ti3SiC2 phase increased and the microstructure became more uniform because of Ti/Si/C/Cr element diffusion. The average micro-hardness of plasma-sprayed 3Ti–Si–2C–Cr coating improved by 2% after annealing at 800 °C and its average fracture toughness improved by 18%. The average micro-hardness of plasma-sprayed 3Ti–Si–2C-1.5Cr coating improved by 9% after annealing at 1100 °C and its average fracture toughness improved by 22%. The improved mechanical properties were because of the increased MAX-Ti3SiC2 phase, the uniform microstructure and the micro-cracks healing, indicating the annealing treatments were positive for the performance of Ti–Cr–Si–C coatings.