TiC Alloy Research Articles

Microstructures, Mechanical Properties and Thermal Conductivities of W-0.5 wt.%TiC Alloys Prepared via Ball Milling and Wet Chemical Method

Two kinds of W-0.5 wt.%TiC alloys were prepared, one by ball milling and the other by the wet chemical method. For comparison, pure tungsten powders were chemically prepared and sintered by the same process. The microstructures, mechanical properties and thermal conductivities of the prepared samples were characterized. It has been found that the wet chemical method resulted in finer sizes and more uniform distribution of TiC particles in the sintered tungsten matrix than the ball milling method. The W-TiC alloy prepared by the wet chemical method achieved the highest bending strength (1065.72 MPa) among the samples. Further, it also exhibited obviously higher thermal conductivities in the temperature range of room temperature to 600°C than did the W-TiC alloy prepared by ball milling, but the differences in their thermal conductivities could be ignored in the range of 600–800°C.

Microstructures, Mechanical Properties and Deuterium Blistering Behavior of Chemically Prepared W–TiC Alloys

The sintered W–(0, 0.1, 0.3 and 0.5) wt% TiC alloys and rolled W–0.1 wt% TiC alloys with different rolling reduction rates (65 and 83%) were fabricated using a wet-chemical method. The samples were irradiated with 367 shots of deuterium plasma in the Material and Plasma Evaluation System of the EAST tokamak for a total plasma exposure time of ~2000 s to evaluate their surface blistering behaviors. The microstructure, mechanical properties and surface blistering behavior of the samples after exposure were investigated. It was found that the average grain size of the sintered W–(0–0.5)TiC alloys decreased, and their relative density, microhardness and bending strength increased with the increase in the TiC content. The sintered W–0.5TiC alloy exhibited the smallest average grain size of 0.8 μm and the highest bending strength of 1163.6 MPa. Post-irradiation examinations showed that all of the sintered samples suffered surface blistering, but as the TiC content of the alloy was increased, the size of the blisters decreased. The sintered pure tungsten (PW) exhibited serious, ruptured blisters with sizes of ~1 to 25 μm; while the sintered W–0.5TiC alloy exhibited the best resistance to the deuterium plasma as evidenced by the small size of the blisters of <1–2 μm. In the case of the rolled samples, stream-like blisters and spot-like blisters were observed on the surfaces of the W–0.1 wt% TiC alloys with rolling reduction rates of 65 and 83%, respectively. The W–0.1 wt% TiC alloy with a higher rolling reduction rate exhibited a lower density of blisters and a lower degree of damage, which demonstrated that higher rolling reduction rate improved the deuterium plasma resistance of the rolled W–TiC alloys.

Thickness-dependent phase evolution and bonding strength of SiC ceramics joints with active Ti interlayer

A robust solid state diffusion joining technique for SiC ceramics was designed with a thickness-controlled Ti interlayer formed by physical vapor deposition and joined by electric field-assisted sintering technology. The interface reaction and phase revolution process were investigated in terms of the equilibrium phase diagram and the concentration-dependent potential diagram of the Ti-Si-C ternary system. Interestingly, under the same joining conditions (fixed temperature and annealing duration), the thickness of the Ti interlayer determined the concentration and distribution of the Si and C reactants in the resulting joint layer, and the respective diffusion distance of Si and C into the Ti interlayer differentiated dramatically during the short joining process (only 5min). In the case of a 100nm Ti coating as an interlayer, the C concentration in the joint layer was saturated quickly, which benefited the formation of a TiC phase and subsequent Ti3SiC2 phase. The SiC ceramics were successfully joined at a low temperature of 1000°C with a flexural strength of 168.2MPa, which satisfies applications in corrosive environments. When the Ti thickness was increased to 1μm, Si atoms diffused easily through the diluted Ti-C alloy (a dense TiC phase was not formed), and the Ti5Si3 brittle phase formed preferentially. These findings highlight the importance of the diffusion kinetics of the reactants on the final composition in the solid state reaction, particularly in the joining technique for covalent SiC ceramics.

Microstructure and properties of in-situ synthesized Cu-1 wt%TiC alloy followed by ECAP and post-annealing

A dispersion-strengthened copper alloy with 1wt% TiC for commercial electrical-contact wires was prepared by in-situ reaction casting, grain-ultrafining by equal-channel angular pressing (ECAP) and subsequent annealing with aim to obtain excellent comprehensive performance. The results showed that fine TiC particles were in-situ synthesized in the as-cast Cu matrix and aggregated in clusters, and thus mechanical properties of the as-cast alloy deemed insufficient. Continued ECAP at 473K significantly refined the grains of the as-cast alloy and improved the distribution of TiC particles. Due to multiple strengthening mechanisms, the ECAP-processed alloys maintained good conductivity with obviously enhanced tensile strength and hardness values. After post-ECAP annealing, the elongation and conductivity of the fine-grained copper alloy increased with the adequate tensile strength. The novel combined process endows the alloy appropriate performance to serve current high-frequency electrification railway systems.

Mechanical properties and thermal stability of rolled W-0.5 wt% TiC alloys

In this paper, hot rolled W-0.5wt% TiC alloys are fabricated via a combination of powder metallurgy and subsequent hot rolling with 65% thickness reduction. The as-rolled alloys show high strength of 789MPa at 200°C with a total elongation of 4.8%. We have explored the mechanical properties and thermal stability of W-0.5wt% TiC alloys after annealing at various temperature. The corresponding results show that hardness and fracture strength slightly decrease with increased annealing temperature up to 1500°C owing to recovery. While after annealing at 1600°C for 1h, the fracture strength of W-0.5wt% TiC alloys decreases significantly due to full recrystallization and grain growth. The thermal conductivity increases with increased annealing temperature. The observed incubation time for recrystallization and the corresponding recrystallization thermal activation energy (~612kJ/mol) for this rolled plates indicate a sufficient thermal stability at service temperature below 1200°C. This good thermal stability is attributed to the nanosized TiC dispersion strengthened structures.

耐摩耐食用超硬合金の研究開発

Ti-8.4 vol% M-47.4 vol% TiC (M: Cr, Mo, W) alloys were prepared through P/M technology and their microstructures and mechanical properties were investigated. It was noted that TiC grain size of W alloy was much smaller than that of both Cr alloy and Mo alloy. Smaller diffusion coefficient of M in β-Ti phase and smaller absolute value of Helmholtz standard free energy of formation of MC were thought to suppress TiC grain growth. It was found that hardness and transverse-rupture strength of W alloy were much higher than those of both Cr alloy and Mo alloy.

Microstructure, basic thermal–mechanical and Charpy impact properties of W-0.1 wt.% TiC alloy via chemical method

W-0.1 wt.% TiC materials with different rolling reduction (65% and 83%) were fabricated by wet chemical method, medium-frequency induction sintering and hot rolling and their microstructures, chemical composition, basic mechanical properties, high temperature tensile properties and Charpy impact properties were characterized. For comparing, commercial pure tungsten powders were sintered and hot rolled with the same procedure. The results revealed that the heavily elongated TiC particles were uniformly distributed in the grain interiors. In addition, the intragranular TiC particles combining with severe plastic deformation could refine the grain size and increase both the strength and toughness of tungsten materials remarkably. The W–TiC alloy with rolling reduction of 83% exhibited the highest bending strength of 1260 MPa, the highest tensile elongation of 19.3% and 13.6% at 300 and 600 °C respectively, the highest Charpy absorbed energies at 400–900 °C and the lowest DBTT of about 450 °C. In contrast, the pure tungsten with the same rolling reduction displayed the lowest bending strength of 1035.4 MPa, the lowest tensile elongation of 12.1% and 9.3% at 300 and 600 °C respectively, the much lower Charpy absorbed energies at 400–900 °C and the higher DBTT of 650 °C. Interestingly, pure tungsten with more rolling reduction resulted in larger grain size due to their low recrystallization temperature. Conversely, the W–TiC alloys achieved smaller grain size with more rolling reduction due to the elevated recrystallization temperature by the addition of TiC particles. Another interesting phenomenon is that the total tensile elongations of the samples tested at 600 °C were all lower than the samples tested at 300 °C. The reason was attributed to the different moving behavior of the dislocations at different tensile test temperatures.

Preparation and microstructure characterization of W–0.1 wt.%TiC alloy via chemical method

W–0.1wt.%TiC materials with and without the addition of PVP were fabricated by wet-chemical method and spark plasma sintering. The microstructures were characterized by FESEM and TEM. The results revealed that the addition of PVP remarkably improved the uniform dispersion of TiC particles during the synthesis process. W–TiC without PVP showed dispersoids with size of 100–1000nm were distributed unevenly in the tungsten matrix; only a few particles with the size of about 80–300nm were located in tungsten grain interior. Conversely, the microstructure of W–TiC with PVP showed that dispersoids were dispersed well and kept about 80nm. Moreover, the majority of them were uniformly distributed in the grain interior. The EDS analyses revealed that the dispersoids were composed of Ti, C, O and W. TEM observations further verified that the dispersoids were TiC particles. W–TiC with PVP showed better mechanical properties when compared with the samples of W–TiC without PVP and pure tungsten.

FeSn2–TiC nanocomposite alloy anodes for lithium ion batteries

FeSn2–TiC nanocomposite alloy anodes for lithium-ion batteries have been synthesized by a mechanochemical process involving high-energy mechanical milling of Fe/Ti, Ti/Sn, and carbon black. Characterization of the nanocomposites formed with x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) reveals that this alloy is composed of crystalline nanoparticles of FeSn2 dispersed in a matrix of TiC. The FeSn2–TiC alloy shows an initial gravimetric capacity of 511 mAh g−1 (1073 mAh cm−3) with a first-cycle coulombic efficiency of 77% and a tap density of 2.1 g cm−3. The TiC buffer matrix in the nanocomposite anode accommodates the large volume change occurring during the charge–discharge process and leads to good cyclability compared to similar Sn-based anodes.

Corrosion Behaviour of TiC-Reinforced Hadfield Manganese Austenitic Steel Matrix In-Situ Composites

The corrosion behaviour of Hadfield manganese austenitic steel matrix composite reinforced with the varying amount of TiC and unreinforced Hadfield manganese austenitic steel matrix alloy has been evaluated in 3.5% NaCl aqueous solution with the pH value of 6 by the potentiodynamic polarization curves and linear polarization resistance measurements at a scan rate of 1 mV/s at room temperature (25°C ± 2°C). The corrosion rate of the composites is higher than that of their unreinforced matrix alloy and it increases with the increasing volume fraction of TiC. The poor corrosion resistance of the composites can be attributed to the galvanic effects between the matrix and reinforcement.

Preparation and characteristics of W–1 wt.% TiC alloy via a novel chemical method and spark plasma sintering

A chemical method was used to synthesize W/TiC composite powder. The obtained powder can achieve near full densification (relative density of 99.0%) after sintering by spark plasma technology at 1800°C for 3min. Field-emission scanning electron microscopy and transmission electron micrographs showed that doped TiC nano-particles existed at the grain interior and grain boundary. Transgranular and intergranular fractures can be observed on the surface of the sintered sample. The thermal conductivity of the sintered specimen was 122.89W/mK at room temperature and has high thermal stability at high temperature. The specimen was uniformly organized on the basis of its microhardness after heat-treated at 1200°C and 1300°C.

Self-propagating high-temperature synthesis of highly dispersed titanium-carbide phase from powder mixtures in the aluminum melt

The self-propagating synthesis (SHS) of titanium carbide particles in an aluminum melt made from a mixture of titanium and carbon powders with the addition of a chloride-containing flux, aluminum, or haloid salt (Na2TiF6) during the fabrication of the Al-10% TiC alloy is investigated. It is shown that the use of these additives makes it possible to reduce the size of synthesized particles of the TiC carbide phase to ultradispersed (0.17–0.35 μm) and nanosize (smaller than 0.1 μm) levels.

Evaluation of Tool Performance of Recycle-Type Fe&lt;sub&gt;3&lt;/sub&gt;Al Based Alloy for Pure Cu

Recycle-type Fe3Al (hereinafter designated as Re-Fe3Al) based alloys reinforced by the carbides of TiC or ZrC were processed by the high frequency induction melting method using a high-carbon Cr steel sludge, Al can scraps and the transition metals of Ti or Zr. The carbides were synthesized by in-situ reaction between the transition metal and carbon in the molten iron aluminum alloy. Vickers hardness values are 309HV0.5 for Re-Fe3Al/TiC alloy, and 473HV0.5 for Re-Fe3Al/ZrC alloy, which are higher than that of P-Fe3Al (preprared from pure-Fe and-Al). The cutting performance of the Re-Fe3Al baed alloys was compared with a High-Speed-Steel (HSS) by cutting tests for pure-Cu extruded bar (C1020) using a lathe under a dry condition. Tool life limit was estimated from frank wear length after the cutting tests of C1020 by finish-machining. Tool life limit of Re-Fe3Al/TiC alloy is more than16 min; P-Fe3Al was 12 min; HSS was 8 min, Re-Fe3Al/ZrC alloy was 7 min at the cutting speed of 100m/min. Also, tool life limit of the Re-Fe3Al/TiC alloy was more than twice times as long as that of the HSS at the cutting speed of 300/min. The relationship between cutting speed and tool life limit clearly indicated that the Re-Fe3Al/TiC alloy was better than the HSS at a higher cutting speed. Therefore, it was concluded that Re-Fe3Al/TiC alloy has excellent cutting tool performance.

Effect of Solution Treatment on the Microstructure of Ti-C Alloys

The work concerns a new group of titanium alloys with properties improved due to the presence of carbon. Investigated alloys were melted in a vacuum induction furnaces with copper water cooled crucibles. It was showed the influence of the solution temperature in range of 875 to 975oC on the number, size and distribution of carbides in pure titanium with content of 0.2 wt.% carbon and on the hardness test of researched alloys. The observed changes in the microstructure and properties are the result of phase transformations taking place during heating: α + TiC α α + β β + TiC.

Creep behavior of two Cu-2 vol% TiC alloys obtained by reaction milling and extrusion

The creep behavior of two Cu-2vol% TiC alloys prepared by reaction milling and extrusion are presented. Creep tests were performed at 773–1123K. The activation energy values between 109 and 156kJ/mol and the stress-exponent values between 3.1 and 6.3 indicated that no dispersion-strengthening effect occurred.

Microstructure Characterization of Tungsten Based Alloys for Fusion Application

The microstructure of two tungsten based alloys (W-1.1%TiC and W-1.7% TiC) was characterized using light microscopy, analytical electron microscopy and electron tomography. These alloys represent a class of W based dispersion strengthened alloys with TiC used as strengthening particles. Addition of TiC leads to improved creep resistance and tensile strength of the W based alloys. The results show that the W-1.7%TiC alloy exhibits large scatter in grain size, much higher porosity and contains also Ti-O particles. The W-1.1%TiC alloy has fine grained microstructure with uniformly distributed fine TiC particles within the matrix and low porosity. As a result of the different microstructure, the W-1.1%TiC alloy exhibits better mechanical properties, when compared to the W-1.7%TiC alloy.

Vacuum hot-pressed beryllium and TiC dispersion strengthened tungsten alloy developments for ITER and future fusion reactors

Beryllium and tungsten have been selected as the plasma facing materials of the ITER first wall (FW) and divertor chamber, respectively. China, as a participant in ITER, will share the manufacturing tasks of ITER first-wall mockups with the European Union and Russia. Therefore ITER-grade beryllium has been developed in China and a kind of vacuum hot-pressed (VHP) beryllium, CN-G01, was characterized for both physical, and thermo-mechanical properties and high heat flux performance, which indicated an equivalent performance to U.S. grade S-65C beryllium, a reference grade beryllium of ITER. Consequently CN-G01 beryllium has been accepted as the armor material of ITER-FW blankets. In addition, a modification of tungsten by TiC dispersion strengthening was investigated and a W–TiC alloy with TiC content of 0.1wt.% has been developed. Both surface hardness and recrystallization measurements indicate its re-crystallization temperature approximately at 1773K. Deuterium retention and thermal desorption behaviors of pure tungsten and the TiC alloy were also measured by deuterium ion irradiation of 1.7keV energy to the fluence of 0.5–5×1018D/cm2; a main desorption peak at around 573K was found and no significant difference was observed between pure tungsten and the tungsten alloy. Further characterization of the tungsten alloy is in progress.

Property change of advanced tungsten alloys due to neutron irradiation

This study investigates the effect of neutron irradiation on the functional properties of pure tungsten (W) and advanced tungsten alloys (e.g., lanthanum (La)-doped W, potassium (K)-doped W, and ultra-fine-grained (UFG) W–TiC alloys) tested in the Japan Materials Testing Reactor (JMTR) or experimental fast reactor Joyo. The irradiation temperature and damage were in the range 804–1073K and 0.15–0.47dpa, respectively. TEM images of all samples after 0.42dpa irradiation at 1023K showed voids, black dots, and dislocation loops, indicating that similar damage structures were formed in pure W, La-doped W, K-doped W, and UFG W–0.5wt% TiC. The electrical resistivity of all specimens increased following neutron irradiation. Nearly identical electrical resistivity and irradiation hardening were observed in pure W, La-doped W, and K-doped W. The electrical resistivity of UFG W–TiC was higher than that of other specimens before and after irradiation, which may be attributed to its ultra-fine-grain structure, as well as the presence of impurities introduced during the alloying process. Compared to the other specimens, the UFG W–TiC was more resistant to irradiation hardening.

Characteristics of Corrosion Resistance of Ti-C Alloys

This paper presents the results of testing the corrosion resistance of pure Ti and Ti6Al4V alloy improved by carbon addition at the level of 0.2 and 0.5 wt.%. The testing was carried out at room temperature in HNO3 acid solution (40%) and HCl acid solution (5 and 10%). It has been established that carbon addition affects the improvement in electrochemical corrosion resistance of pure Ti and Ti6Al4V alloy in HNO3 solution, whereas the higher carbon content the better corrosion resistance of Ti. For Ti6Al4V alloy the increase in corrosion resistance is caused by carbon addition at the level of 0.2 wt.%. The result of the corrosion resistance of both pure Ti and Ti6Al4V alloy with carbon in a solution of HCl indicates that the more detrimental is the solution of lower concentration

The Structure of High-Quality Aluminium Cast Iron

In this study presents the analyse of aluminium iron cast structure (as-cast condition) which are used in high temperature. While producing the casts of aluminium iron major influence has been preserve the structure of technological process parameters. The addition to Fe-C-Al alloy V, Ti, Cr leads to the improvement of functional and mechanical cast qualities. In this study, a method was investigated to eliminate the presence of undesirable Al4C3 phases in a aluminium cast iron structure and thus improve the production process. V and Ti additions in aluminium cast iron allows to development of FeAl - VC or TiC alloys. In particular, V or Ti contents above 5 wt.% were found to totally eliminate the presence of Al4C3. In addition, preliminary work indicates that the alloy with the FeAl - VC or TiC structure reveals high oxidation resistance. The introduction of 5 wt.% chromium to aluminium cast iron strengthened Al4C3 precipitate. Thus, the resultant alloy can be considered an intermetallic FeAl matrix strengthened by VC and TiC or modified Al4C3 reinforcements.