Amount Of Ti Research Articles

Qia’erdunbasixi Fe–Cu Deposit in Sawur, Xinjiang: A Case Study of Skarn Deposit Hosted by Volcanic Rock

The Sawur Cu–Au belt, northern Xinjiang, China, is the eastward extension of the Zarma–Sawur Cu–Au belt in Kazakhstan, where Late Paleozoic volcanic rocks and intrusions are highly developed. The Qia’erdunbasixi Fe–Cu deposit in Sawur is a recently discovered deposit and is still under exploration. The intrusive rocks are syenite and diorite, and the wall rocks consist of andesite and minor basalt, lamprophyre, and tuff. The U–Pb SHRIMP zircon age of the Qia’erdunbasixi syenite intruding into the volcanic rocks is 345 ± 2.2 Ma (MSWD = 1.3), presenting as the lower limit of skarn Fe mineralization. The intrusives belong to the calc–alkaline to high-K calc-alkaline series with large ion lithophile element (LILE) enrichment, high LREE/HREE fractionation, and high field strength element (HFSE) depletion. The initial 87Sr/86Sr ratios of the Qia’erdunbasixi syenite range from 0.70403 to 0.70420, and the εNd(t) values are from +5.5 to +6.8, which are the typical characteristics of island arc igneous rocks. Diorites having similar REE features with syenite should share the same magma source. Magnetite and copper mineralization develop mostly along the contact zones of syenite and diorite, respectively. Fe mineralization develops along the contact zone of syenite, with typical skarn zonation. The metallogenesis event can be divided into the prograde skarn stage (diopside–augite–andradite–magnetite–calcite–quartz), retrograde skarn stage (epidote–chlorite–actinolite–K-feldspar–calcite–magnetite–quartz), and quartz–sulfide stage (quartz–magnetite–K-feldspar–calcite–sercite–chlorite–actinolite–prehnite–chalcopyrite–pyrite). The early–mid-stage magnetite with certain amounts of Ti and V was crystallized from magma, while the late-stage magnetite has the typical characteristics of hydrothermal calcic skarn magnetite. The temperature of mineralization is between 350 and 450°C based on mineral assemblages and phase diagrams. Copper mineralization is concentrated along the outer contact zone of the diorite. Paragenesis sequences of the four stages of mineralization could be identified for copper mineralization: 1) albite–quartz; 2) chalcopyrite–pyrite–gold–seriate–quartz; 3) chalcopyrite–pyrite–epidotic–reunite; and 4) sphalerite–galena–quartz–calcite. Qia’erdunbasixi is a composite deposit with skarn-type Fe mineralization and mesothermal Cu mineralization and has a genetic relationship with magmatism in an island arc setting.

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H 2 O 2

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H ₂ O ₂

Ti modification to improve the cyclic stability of Ni-rich LiNi0.83Co0.11Mn0.06O2 cathode materials by suppressing mechanical fracture

The rapid capacity decay is one of the main reasons to hinder the wide industrial application of the Ni-rich ternary cathode materials for lithium-ion batteries (LIBs). Ti-doping has been systematically studied to overcome this problem. Ti doping can improve mechanical stability, reduce strain, maintain structural integrity, and thus improve electrochemical performances. After 200 cycles, the capacity retention of the 424Ti0.2-NCM sample reaches 89.9% in the voltage range of 2.8–4.5 V, and the initial capacity does not decrease significantly (197.0 mAh g-1). Our results also show that the cycle performance is related not only to the doping amount of Ti but also to the doping method, which can affect the microstructure of cathode particles. The grains of the outer layer of the modified NCM cathode particles obtained by the co-precipitation method are distributed along the radial direction, while grains in the core are equiaxed. And there is also a significant difference in the porosity of the two locations. A moderate amount of porosity in the core can help release the internal stress and avoid the fracture of the particles, which contributes to improved cycling performance.

Effect of Ti Addition on Yield Strength of Low‐Mo Fire‐Resistant Steel at Elevated Temperatures

Herein, a series of low‐Mo (0.2 wt%) fire‐resistant steels with varying amounts of Ti (0.008–0.13 wt%) are investigated to study the effects of Ti on yield strength at elevated temperatures. At room temperature (RT), precipitation strengthening by nanoscale TiC precipitates is found to be the major factor for the enhanced strength. The amount of TiC precipitates and both the yield and tensile strengths increase monotonically with the Ti content. However, the yield strength ratio (YS at 600 °C divided by YS at RT) of the steel with the highest Ti content (0.13 wt%) is significantly reduced to 0.6. In contrast, the YS ratio of the steels with Ti content in the range of 0.008–0.087 wt% remains above 0.7 and increases with Ti content. The difference between the steels lies in the B content and the resultant bainite volume fraction. The steel with 0.13 wt% Ti does not contain B and has only 4% bainite, whereas the other steels contain 20 ppm B and approximately 60% bainite. Hence, a microstructure with a sufficient fraction of bainite is required to ensure strength at elevated temperatures. The properties can be further improved by Ti precipitation strengthening.

Physicochemical Characterization and Antibacterial Activity of Titanium/Shellac-Coated Hydroxyapatite Composites

Titanium and hydroxyapatite are widely used as materials for implants. Titanium has good mechanical properties, good corrosion resistance, and a high modulus of elasticity. Hydroxyapatite has good biocompatibility, bioactivity, and significant osteoinductivity. In this study, powder metallurgy was used as a method to combine titanium and hydroxyapatite for use in implants. Shellac was used as a binder between ceramic and metal due to its lower melting point. The surface morphology and chemical properties were evaluated by scanning electron microscopy–energy dispersive X-ray (SEM-EDX), whereby the SEM revealed the appearance of micropores in the Ti-HA composites during the sintering process, and the EDX showed that the final product had high amounts of Ti and Ca and low P. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses were used to achieve the chemical characterization of composites, whereby a weak diffraction peak was observed in the XRD spectrum of Ti-HA composites, and the FTIR analysis confirmed that the composites had carbonate (CO3)2−, phosphate (PO4)3−, and hydroxyl (OH)− groups. Oxygen was sufficient due to the sintering process being conducted in an air environment. The antibacterial activities were characterized using the disc diffusion method with Escherichia coli and Staphylococcus aureus bacteria, whereby the prepared Ti-HA composites had a greater antibacterial effect on E. coli than on S. aureus. Finally, pH changes were observed during the 24 h incubation. The result showed that the Ti-HA composite did not contain chemical compounds that could cause harmful effects for humans and had good antibacterial activity against E. coli.

Atomic-scale characterization of the oxidation state of Ti in meteoritic hibonite: Implications for early solar system thermodynamics

Abstract Calcium-aluminum-rich inclusions (CAIs) in chondritic meteorites are composed of refractory minerals thought to be the first solids to have formed in the solar nebula. Among them, hibonite, nominally CaAl12O19, holds particular interest because it can incorporate significant amounts of Ti into its crystal structure in both Ti3+ and Ti4+ oxidation states. The relative amounts of these cations that are incorporated reflect the redox conditions under which the grain formed or last equilibrated and their measurement can provide insight into the thermodynamic landscape of the early solar nebula. Here we develop a new method for the quantification of Ti oxidation states using electron energy-loss spectroscopy (EELS) in an aberration-corrected scanning transmission electron microscope (STEM) to apply it to hibonite. Using a series of Ti-bearing oxides, we find that the onset intensity of the Ti L2,3 edge decreases with increasing Ti-oxidation state, which is corroborated by simulated Ti-oxide spectra using first-principles density-functional theory. We test the relationship on a set of synthetic hibonite grains with known Ti4+/ΣTi values and apply the developed method on a hibonite grain from a compact type A inclusion in the Northwest Africa (NWA) 5028 CR2 carbonaceous chondrite. The STEM-EELS data show that the chondritic hibonite grain is zoned with a Ti4+/ΣTi ratio ranging from 0.78 ± 0.04 to 0.93 ± 0.04 over a scale of 100 nm between the core and edge of the grain, respectively. The Ti substitution sites are characterized by experimental and calculated high-angle annular-dark-field (HAADF) images and atomic-level EEL spectrum imaging. Simulated HAADF images reveal that Ti is distributed between the M2 and M4 sites while Mg sits on the M3 site. Quantitative energy-dispersive X-ray spectroscopy shows that this grain is also zoned in Al and Ti. The Mg distribution is not well correlated with that of Ti and Ti4+/ΣTi at the nanoscale. The spatial decoupling of the element composition and Ti-oxidation states suggests a multistage evolution for this hibonite grain. We hypothesize that Ti and Mg were incorporated into the structure during condensation at high temperature through multiple reactions. Transient heating, presumably in the solar nebula, adds complexity to the crystal chemistry and potentially redistributed Ti and Mg. Concurrently, the formation of oxygen vacancies as a result of a reducing gas, led to the reduction of Ti4+ to Ti3+. The multiple defect reactions occurring in this single hibonite crystal preclude a simple relationship between the Ti4+/ΣTi and the fO2 of formation. However, moving forward, these measurements are fundamental inputs for modeling of the thermodynamic conditions under which hibonite formed in the early solar nebula.

Bioleaching Performance of Titanium from Bauxite Residue Under a Continuous Mode Using Penicillium Tricolor.

The present study performed a continuous mode of bioleaching to investigate the leaching efficiency of Titanium (Ti) from bauxite residue using Penicillium Tricolor at between 4% and 12% pulp densities during a 120-day running. Obtained results of the current study showed that increased pulp density led to a decrease in biomass, dissolved oxygen, and amount of leaching Ti as well as an increase in pH value. Further, it was found that efficiency of bioleaching can be enhanced by increasing the rate of aeration, retention time, and concentration of carbon source. However, it was also evident that, at high pulp density, excessive agitation did not give an expected leaching efficiency but a collapse of biomass. In addition, results of the present study showed that the maximum leaching amount of Ti was 3202mg/L with a corresponding leaching ratio of 50.35% during the whole bioleaching process. Moreover, it was noted that the biomass showed a significant negative correlation with the pH value and dissolved oxygen. However, the biomass showed a significant positive correlation with leaching amount of Ti and thus indicate that microbial metabolic activities are the uppermost factor affecting the continuous leaching performance.

Laser Preheating for Hot Crack Reduction in Direct Metal Deposition of Inconel 738LC

Welding of precipitation-hardenable nickel-based super alloys that contain large amounts of Al and Ti is challenging due to their high susceptibility to hot cracking. For metal additive manufacturing (AM) by powder bed fusion (PBF) or direct metal deposition (DMD), various welding process adjustments may prevent the formation of cracks. The aim of this study is the development and experimental characterization of a laser preheating process for DMD of Inconel 738LC. Metallographic cross-sections of multiple test specimens were analyzed to quantify the effect of initial substrate temperature, specimen geometry, deposition parameters, and scanning strategy on the resulting crack density. The results show that increased substrate temperature by laser preheating and reduced specimen size leads to crack-free deposited structures. Therefore, the proposed preheating process may be applied for part fabrication or repair by DMD to reduce or even completely prevent the risk of hot cracking.

Phase equilibria in Ni–Ti–Ta ternary system

Phase diagrams of two isothermal sections of the Ni–Ti–Ta ternary system at 1000 and 1200 °C in a full composition range were determined by X-ray diffraction and electron probe microanalysis. The experimental results indicated a ternary compound τ phase with low solid solubility and composition ranges of (16.3–22.4) at.% Ta, (15.9–24.1) at.% Ti and (58.5–60.0) at.% Ni at 1000 °C. The two terminal solid solutions (bcc-(Ta) and β-Ti) formed a continuous solid solution at 1000 and 1200 °C. A certain amount of Ti can dissolve into Ni–Ta intermetallic compounds near the Ni–Ta side, with the highest value of 21.9 at.% observed in the Ni2Ta compound at 1000 °C.

Variable range hopping conduction mechanisms in reduced rutile TiO2

In this study, obtained samples via reducing Rutile TiO2 by Mg are analyzed to determine the titanium suboxide phases and the dominant structural phase in each sample. By increasing the heat treatment temperature or the amount of reducing agent (Mg), the amount of suboxide phases Ti n O2n−1 (1 ≤ n < 10) with the lower n values increases, and TiO is the main phase in the samples with a low electrical resistivity. The hopping conduction mechanism is also investigated in the temperature range of 11.5–300 K, and the characteristic parameters describing the conduction mechanism are determined and discussed. For samples with a low electrical resistivity, the nearest neighbor hopping (NNH) conduction mechanism governs the charge transport properties below 220 K, and a transition from the NNH to the Mott-variable range hopping (VRH) conduction regimes is observed at ∼65 K. In addition, the Efros-Shklovskii (ES)-VRH conduction process governs at low temperatures below 18 K, and the last crossover from the Mott-VRH to the ES-VRH models illustrates the strong electron-electron Coulomb interaction, which leads to the Coulomb gap (∼1 meV) at low temperatures. According to the obtained hopping parameters, the low resistivity samples are close to the metal-insulator transition. For samples with a high electrical resistivity, the hopping conduction relations are not fitted to the resistivity-temperature curves, and probably it is related to the resistive switching behavior of the material, which changes the nature and conductivity properties, and is depicted in the current-voltage (I-V) curve.

Barium, Lithium and Titanium Content in Herbs of Mid-Field Wet Depressions in East-Central Poland

This paper presents the results of research on the Ba, Li and Ti content in six species of herbs sampled from mid-field wet depressions and from the soil. These temporary flooded depressions were surrounded by arable crops, permanent grassland and shrubby vegetation. The research area was located in the eastern part of the Mazovian Voivodeship, east-central Poland. The following plants were used in the experiment: corn mint (Mentha arvensis L.), purple marshlocks (Comarum palustre L.), silverweed (Potentilla anserina L.), yarrow (Achillea millefolium L.), yellow loosestrife (Lysimachia vulgaris L.) and gypsy-wort (Lycopus europaeus L.). The Li, Ba and Ti content of plants, bottom sediment and soil was determined by the ICP-AES method after previous dry mineralization. Of the six herb species, Mentha arvensis L. was with the greatest accumulation potential of the chemical elements. However, no excessive Ba, Li and Ti content was found in herbs growing at different distances from arable fields, permanent grassland and shrubby vegetation. The highest Ba content was found in periodically flooded soil (zone II), while the highest amounts of Li and Ti were recorded in non-flooded soil (zone III).

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.

Corrosion characteristics of Mo and TZM alloy for plasma facing components in molten lithium at 623 K

In this study, the corrosion behaviours of molybdenum (Mo) and a Mo-based alloy (TZM) were investigated using a static immersion corrosion technique. Weight loss, surface microstructure, and corrosion depth of Mo and the TZM alloy were correlated with elements. The compatibility of Mo and the TZM alloy in static liquid Li was suitable. Mo demonstrated uniform corrosion with a homogenous dissolution of free C and Mo, and TZM alloy exhibited a nonuniform corrosion behaviour with a preferential grain boundary attack caused by the selective dissolution of free C, Ti, and Zr. When the surface oxidation layer of the samples was consumed, free C from Mo and TZM diffused into molten Li to form Li2C2 and then was captured by Zr, Ti, and Mo to form thermodynamically stable carbides, which resulted in the enrichment of the C layer near the sample surfaces. In addition, Ti and Zr acted as N-trappers in liquid Li; the formation of Zr and Ti nitrides resulted in the enrichment of N, Ti, and Zr elements on the surface and led to TZM corrosion increase. Thus, Zr and Ti depletion, pitting, and grain boundary corrosion were problematic for TZM under long-term exposure to liquid Li. Reducing the content of free C and nonmetallic N and increasing the amount of Ti and Zr carbides on the surface of and inside the raw TZM alloy helped improve the corrosion resistance of TZM in liquid Li.

A proposed formation mechanism of the Type-A radiocaesium-bearing microparticles released from Units 2/3 during the Fukushima Daiichi Nuclear Power Plant accident

A large amount of radiocaesium-bearing microparticles (CsMPs) were released into surrounding environment during the Fukushima Daiichi Nuclear Power Plant accident. To clarify the formation mechanism of the Type-A CsMPs, which were released from Units 2/3 and have spherical or ellipsoidal morphologies, oxidation behavior of 304 stainless steel containing 1 wt.% Si at 1200 ºC in steam atmosphere was investigated in this work. Both Fe2SiO4 and Ni-Fe-Cr phases were formed and distributed in the porous oxide scale. With the progress of oxidation, Fe2SiO4 and Ni-Fe-Cr phases were oxidized, causing severe spallation of the oxide scale somewhere between 90 min and 120 min. Trace amounts of Al and Ti were detected in the silica microparticles transformed from Fe2SiO4 oxidation. Furthermore, thermodynamic calculations were performed with the aid of FactSage software, revealing that: (1) when severe spallation of the oxide scale occurs, high levels of Fe oxides can stably exist in silica-based microparticles distributed in the oxide scale; (2) the Type-A CsMPs may be formed in reducing atmospheres. Based on the experimental and thermodynamic results, a completely new formation mechanism of the Type-A CsMPs is proposed. Silicate matrix is inherited from partially oxidized FeO-bearing silica-based microparticles, which are released from the oxide scale due to spallation. Moreover, diffusion of volatile constituents into FeO-bearing silica-based microparticles occurs in the reactor pressure vessel (RPV), not out of the RPV. This new formation mechanism can well explain many characteristics of the Type-A CsMPs.

Characterisation of precipitates in a stainless maraging steel by three-dimensional atom probe and small-angle neutron scattering

Abstract Two complementary techniques, namely three-dimensional atom probe and small-angle neutron scattering, were employed to study precipitation phenomena in a stainless maraging steel (Fe-12.3 %Cr-8.9%Ni-0.6 %Si-1 %Mo-0.6 %Al-0.8%Ti, wt.%) during ageing at 475 °C. Atom probe investigations revealed the precipitation of a single Ni-rich phase exhibiting an average particle diameter of 2.5 nm after 12 h. After ageing for 100 h these precipitates had grown to an average size of 4 nm. In addition, needle-or plate-like Ni-rich precipitates larger than 15 nm were present. Their compositions differ mainly in the amount of Fe, Ni and Ti. Furthermore, Cr-rich precipitates were observed. The size ranges and the number densities of the precipitates match well with those observed by small-angle neutron scattering.

Improvement in bioactivity and corrosion resistance of Ti by hydroxyapatite deposition using ultrasonic mechanical coating and armoring

In the present work, nanostructured hydroxyapatite (HA)-containing coating was prepared on a Ti surface by ultrasonic mechanical coating and armoring (UMCA). A Ti plate was pre-coated with HA slurry, followed by UMCA, which was achieved by high-frequency ZrO 2 ball bombardment. The UMCA process comprised several cycles of pre-coating and ball bombardment, providing high amounts of HA and good coating adhesion. The coating mainly consisted of nano-HA particles (less than 10 nm) and a small amount of Ti. Furthermore, the deformation structures of the Ti surface region were characterized in a nanocrystalline layer with a grain size of 50–200 nm. Additionally, the coating exhibited improved bioactivity and corrosion resistance in Hanks’ balanced salt solution than the Ti surface. Furthermore, the in vitro cytotoxicity test assessed that the HA-containing coating was non-cytotoxic.

The influence of austenitization time and temperature on the austenite grain growth in high Ti-V HSLA steels

Generally, in high titanium-containing high strength low alloy (HSLA) steels, the challenge is to ensure that an adequate amount of Ti dissolves during soaking for precipitate strengthening during cooling or hot working. Therefore, this work focused on the effect of soaking time and temperature on the austenite grain growth kinetics of HSLA steels, of the three alloys containing 0.1 %Ti, and 0 to 0.12 %V. The samples were austenitized at 1150 and 1280 °C for 1, 2 and 3 hrs and quenched in a 10% NaCl brine. Thereafter, the samples were tempered at 490 °C for 72 hrs in order to reveal the prior austenite grain boundaries. The grain size was analysed by the linear intercept method. The precipitation behaviour was predicted by Thermo-Calc software and confirmed by SEM-EDS. At 1150 °C austenitizing temperature, all three steel grades exhibited the Ti (C, N) (Type 1), (Mn-Ti) (C, S) (Type 2), MnS (Type 3 (Ti4C2S2) (Type 4) and TiC (Type 5) precipitates. After escalating the temperature to 1280 °C, only the TiC dissolved. Type 4 and 5 precipitates were the finest and possibly responsible for the grain size refinement. Consequently, alloy 1 with the highest S content of 140 ppm exhibited the finest grain size at both temperatures.

Vacuum arc melted and heat treated AlCoCrFeNiTiX based high-entropy alloys: Thermodynamic and microstructural investigations

The AlCoCrFeNi alloy system is one of the commonly studied high-entropy alloys (HEA). The additional elements like Ti affect the properties of HEAs. In order to predict these effects on the microstructure and the properties of HEAs, a suitable phase diagram is needed. The phase diagrams can be plotted by using thermodynamic software and databases. But experimental studies should be done to control whether this phase diagram is suitable or not. The aim of this study is to propose a phase diagram suitable for the AlCoCrFeNiTiX system by using ThermoCalc software and to compare it with the experimental results. In this work, HEAs were produced by a vacuum arc melting (VAM) method followed by a heat treatment (H-T) process. The stoichiometric amount of Ti was varied-(X = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0). Its effects on the microstructure evaluations and phase transformations in HEAs were investigated. The H-T processes were realized at different temperatures and cooling conditions. The thermodynamic investigations were performed to predict the phases present within as-cast (AC) and heat-treated (HT) HEAs by using Thermo-Calc 2021a Software and its TCHEA4 database. The Calculation of Phase Diagram (CALPHAD) studies were also utilized to plot the phase diagrams for the AlCoCrFeNiTiX system under both equilibrium and non-equilibrium cooling conditions. AC and HT HEAs were characterized by various techniques: scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The phases and the microstructures of AC HEAs were detected as similar to the theoretically obtained alloys under non-equilibrium cooling conditions. While the phases and the microstructures of HT HEAs were detected as similar to the theoretically obtained alloys under equilibrium cooling conditions. As a result, the target alloy composition and production process can be designed depending on the desired properties using the proposed phase diagrams. For example, if the Sigma phase is not desired in the structure, HEAs with Ti1.1 and above contents should be studied.

Effects of sintering temperature and Y2O3/Ti addition on microstructure and hardness of ODS-AlCrFeNi HEAs

Oxide dispersion strengthened (ODS) alloys are leading candidate structural materials for advanced nuclear reactor application due to their excellent high strength and radiation tolerance. In this paper, ODS AlCrFeNi high entropy alloys (HEAs) were synthesized via mechanical alloying (MA) and spark plasma sintering (SPS) to study the effects of sintering temperature (from 1050 °C to 1250 °C) and different Y2O3/Ti addition amounts on the microstructure and hardness. The microstructure was characterized by XRD, SEM, EBSD and HRTEM, and the micro-hardness was tested. The results demonstrated that after MA and SPS, spinodal decomposition occurs in the matrix, in which Fe/Cr enriched disordered BCC phase and Ni/Al enriched ordered B2 phase are formed. At the higher sintering temperature (1250 °C), additional FCC phase appears in 0.3 YT, which is contributed to the formation of higher volume fraction of Al2O3 at powder/grain boundaries so that spinodal decomposition is partly suppressed. At the lower sintering temperature (1100 °C), FCC phase could be formed when Y2O3+Ti amount is lower (0.6 wt%, 1.0 wt%). The hardness of ODS-AlCrFeNi is notably improved when Y2O3 and Ti are added in the same weight percent which is up to 1 wt% or above. The average grain size of 3.0 YT alloy (3 wt% Y2O3+3 wt% Ti) is the smallest, which is 240 nm. The average size of precipitates in 3.0 YT alloy is 8.7 nm, while the number density is the highest (3.3 × 1022/m3). The addition of Y2O3/Ti can modify the types of nanoscale oxides in the ODS-AlCrFeNi. The precipitates in 0Y alloy (without Y2O3 and Ti addition) are Al-rich oxides, while the precipitates observed in 3.0 YT alloy include AlYO3, Al2Y4O9, Y2TiO5, YTiO3, Al2TiO5 and Al2O3. The grain boundary strengthening and precipitation strengthening are dominated in 3.0 YT alloy leading to the highest hardness increment compared with 0Y alloy and the hardness of 3.0 YT alloy reaches 751 HV.

Formation mechanisms of Ti&lt;sub&gt;2&lt;/sub&gt;AlC and Ti&lt;sub&gt;3&lt;/sub&gt;AlC during solid-state sintering between multilayer graphene and TiAl alloy composite

Ti&lt;sub&gt;2&lt;/sub&gt;AlC and Ti&lt;sub&gt;3&lt;/sub&gt;AlC formed by the reaction between C and TiAl alloy can improve the plasticity and strength of TiAl alloy respectively. Generally, the peritectic reaction of L + TiC→Ti&lt;sub&gt;2&lt;/sub&gt;AlC (Ti&lt;sub&gt;3&lt;/sub&gt;AlC) occurs in the process of liquid-phase sintering, but different formation mechanisms of Ti&lt;sub&gt;2&lt;/sub&gt;AlC and Ti&lt;sub&gt;3&lt;/sub&gt;AlC may exist in the solid-state sintering. In this work, multilayer graphene is employed to fabricate the reaction interface with TiAl alloy under 1100–1350 ℃, which is the common solid-state sintering temperature of TiAl alloy. According to the microstructure characterization and analysis, Ti&lt;sub&gt;2&lt;/sub&gt;AlC and Ti&lt;sub&gt;3&lt;/sub&gt;AlC are verified to contain no TiC. The interface energy values of TiC/TiAl, Ti&lt;sub&gt;2&lt;/sub&gt;AlC/TiAl and Ti&lt;sub&gt;3&lt;/sub&gt;AlC/TiAl are calculated to be about 1.2, 0.87 and 0.39 J·m&lt;sup&gt;2&lt;/sup&gt;, respectively, indicating that Ti&lt;sub&gt;2&lt;/sub&gt;AlC and Ti&lt;sub&gt;3&lt;/sub&gt;AlC can be formed directly without TiC mesophase. Besides, only Ti&lt;sub&gt;2&lt;/sub&gt;AlC is observed to be formed at 1150–1250 ℃, while the interface products at 1250–1350 ℃ change into Ti&lt;sub&gt;3&lt;/sub&gt;AlC with a small amount of Ti&lt;sub&gt;2&lt;/sub&gt;AlC. The mechanism that the sintering temperature affects the formation tendency of Ti&lt;sub&gt;2&lt;/sub&gt;AlC and Ti&lt;sub&gt;3&lt;/sub&gt;AlC can be ascribed to the content of α phase. The TiAl alloy matrix is composed of γ and a few α phases at 1150–1250℃, but almost completely transforms into α phase at 1250–1350 ℃, and the increase in the α content can promote the formation of Ti&lt;sub&gt;3&lt;/sub&gt;AlC. The above results demonstrate the possibility of regulating the relative content of Ti&lt;sub&gt;2&lt;/sub&gt;AlC and Ti&lt;sub&gt;3&lt;/sub&gt;AlC through controlling the sintering temperature, which provides a promising method to improve the plasticity and strength of TiAl alloy.