Powder Mixtures Of Ti Research Articles

Effect of the microstructure of SHS powders of titanium carbide–nichrome on the properties of detonation coatings

Experiments are carried out for the self-propagating high-temperature synthesis of TiC–NiCr cermets, implemented in a mechanically activated powder mixture of Ti–C–NiCr in the free combustion mode and under pressure. It is found that an increase in the volume fraction of the binder decreases the size of TiC inclusions in particles obtained by the mechanical grinding of synthesized cermet compacts. A CCDS2000 computerized facility developed at the Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, is used to sputter the coatings. The results of comparison of the characteristics of detonation coatings made from the powders produced in this work and commercial Cr3C2–NiCr powder are given. The prospects of employing the self-propagating high-temperature synthesis of TiC–NiCr powders for the thermal spraying of wear resistant coatings are discussed.

Investigating the microstructure and mechanical properties of Al-TiB2 composite fabricated by Friction Stir Processing (FSP)

Microstructure and mechanical properties of Al-TiB2 composite fabricated by Friction Stir Processing (FSP) were evaluated. In situ TiB2-10wt%Al composite powder was synthesized by mechanical alloying (MA) of Ti, B and Al powder mixture. FSP was applied on AA6063 with and without the addition of TiB2-Al composite powder. Microstructural evaluations showed a nearly uniform distribution of TiB2 in aluminum matrix after FSP with the addition of composite powder. FSP of AA6063 alloy without the addition of reinforcing particles resulted in slight improvement in tensile strength to about 195MPa in comparison to the as-received alloy. By the addition of MAed TiB2-Al composite powder during FSP the tensile strength could increase to about 280MPa which was about 70% higher than that of the base material.

Characterization and hardness of TiCu–Ti2Cu3 intermetallic material fabricated by mechanical alloying and subsequent annealing

In this research, the microstructural and phase evolutions during mechanical alloying (MA) and subsequent heat treatment of Cu–Ti powder mixture are investigated through x-ray diffraction, scanning electron microscopy, transmission electron microscopy and micro-hardness measurements. The obtained experimental results demonstrated that after an optimum MA time of 30 h, TiCu intermetallic compound was achieved with a mean grain size of ≈8 nm and a high micro-hardness value of ≈634 Hv. Annealing the milled powder at different temperatures resulted in formation of major TiCu and Ti2Cu3, and minor Ti2Cu and Cu4Ti nanocrystalline phases, release of internal strain, and coarsening of grains. The amount of TiCu phase and the grain size increased with increase of the annealing temperature. Micro-hardness value of ≈765 Hv was recorded when the milled TiCu powder was annealed at 850 °C. This superior high micro-hardness value can be attributed to formation of higher amount of TiCu phase.

Semisolid Microstructural Evolution during Partial Remelting of a Bulk Alloy Prepared by Cold Pressing of the Ti-Al-2024Al Powder Mixture

A new method, powder thixoforming, has been proposed to fabricate an in situ Al3Tip/2024Al composite. During partial remelting, the microstructural evolution of the bulk alloy prepared by cold pressing of the Ti, Al, 2024Al powder mixture was investigated, and the formation mechanism of the Al3Ti particles produced by the reaction between the Ti powder and the Al alloy melt is also discussed in detail. The results indicate that the microstructural evolution of the 2024 alloy matrix can be divided into three stages: a rapid coarsening of the powder grains; a formation of primary α-Al particles surrounded with a continuous liquid film; and a slight coarsening of the primary α-Al particles. Simultaneously, a reaction layer of Al3Ti can be formed on the Ti powder surface when the bulk is heated for 10 min at 640 °C The thickness (X) of the reaction layer increases with the time according to the parabolic law of . The stress generated in the reaction layer due to the volume dilatation can be calculated by using the equation . Comparing the obtained data with the results of the drip experiment, the reaction rate for the Ti powder and Al powder mixture is greater than that for the Ti plate and Al alloy mixture, respectively.

Diffusion Titanium Aluminizing of Nickel with (Ti, Zr)N Barrier Layer

Background. The prevention of surface oxidation of high-temperature nickel-based alloys is possible by using diffusion coatings, composed of layers of barrier functions. The last inhibit undesirable redistribution of elements at high temperatures. Objective. The aim is to establish the possibility of education in the nickel diffusion titan-aluminum cover with a layer of (Ti,Zr)N, the research phase and chemical composition, structure, properties. Methods. The barrier layer is deposited by physical vapor deposition. Titanium colorizing has been carried out in the powder mixture of Ti, Al, Al 2 O 3 , NH 4 Cl in the container with fusible gate for 4 hours at 1050 °C. The obtained coatings were stu­­- died by modern methods of materials science: X-ray diffraction, microprobe, metallographic and other physic-methods. Results. The possibility of the coating formation on nickel with Ni 2 Ti 4 O, NiTi, Ni 2 AlTi, Ni 3 (Al x Ti 1 - x ) compounds, and the transition zone is established as well as the effect of the thickness of the barrier layer (Ti,Zr)N on the coating structure. The barrier layer thickness of 5.5–6.0 microns promotes the formation of jointing zone above the (Ti,Zr)N layer restricts a thickness of the transition zone, eliminates the formation of the Ni (Al,Ti) layer in the jointing zone, and Ni (O)layer in the transition zone. Conclusions. It is found that during the process of titaniumaluminizing of nickel diffusion zone is formed on the basis of oxides, intermetallic compounds of titanium and aluminum, of (Ti,Zr)N layer with high micro hardness. The investigated coating may be promising for the production of nickel and its alloys at high temperature operating conditions.

Pore and microstructure change induced by SiC whiskers and particles in porous TiB2–TiC–Ti3SiC2 composites

TiB2–TiC–Ti3SiC2 porous composites were prepared through a plasma heating reaction using powder mixtures of Ti, B4C SiC whiskers (SiCw) and SiC particles (SiCp). The effects of the SiCw and SiCp content on pore structures, phase constituents, microstructure, and crystal morphology of TiC were studied. The results show that TiC, TiB, Ti3B4 phases are formed within the 5Ti+B4C system. With the addition of SiCw and SiCp, the TiB and Ti3B4 phases are reduced, sometimes even disappeared. Interestingly, the content of TiB2 and TiC increased, resulting in Ti3SiC2 and TiSi2 being formed. The porosity of composites increases notably with the addition of SiCw. However, with the increase of SiCp, the porosity of the composites first decreases, followed by an increase. After adding the specified amount of SiCw/SiCp, the compressive strength of composites are improved significantly. Additionally, the pore size of the composites are decreased significantly with the addition of SiCw/SiCp. During the plasma heating process, some Si atoms will diffuse into the TiC lattice, which in turn made the cubic TiC grains into hexagonal lamellar TiC or Ti3SiC2 grains.

Tribological Properties of In Situ Composite Obtained from Sintered Mg-Ti-Al Powder Mixture

In the experiment reported in this paper, the friction coefficient (μ) and the mass loss of the metal matrix composite obtained from a powder mixture of Mg, Ti and Al sintered at 640, 650 and 660ºC, with the other parameters held constant, were determined in the dry sliding test at the total distance of 120 m. The sliding speeds of 0.06, 0.09 and 0.14 m/s, and the loads of 2.3, 5 and 9.3 N were applied, as well as a slider made of the EN-GJL300 cast iron. The value of the friction coefficient decreased with the speed and the load, and, for most of the applied friction parameters, it was very low (0.025-0.2). Some influence of the sintering temperature on the mean value of μ and the profile of μ versus the friction distance curve was revealed, yet in the case of the lowest friction speed and load only. An increase of the composite mass loss with the load was revealed, but the wear was generally very low. For a characterization of the composite and its surface after tribological tests, a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) was employed. On the worn surface, effects of abrasion and deformation were visible, but no Ti particle degradation or pulling out were found.

Ultrafine-grained Al composites reinforced with in-situ Al3Ti filaments

Ultrafine-grained (UFG) Al matrix composites reinforced with 15 and 30vol% in-situ Al3Ti filaments were fabricated by extrusion of Al–Ti powder mixtures followed by solid-state reactive diffusion. Fine Al powder particles (1.3µm) heavily deformed the coarser Ti particles (24.5µm) into filaments during extrusion. Upon a subsequent operation of hot isostatic pressing (HIP), the micrometric Al3Ti filaments elongated along the extrusion direction and formed in situ in the UFG Al matrix. Fabricated composites are free of pores and voids with perfect bonding created at the Al–Al3Ti interfaces. In parallel, a small portion (2.4vol%) of nanoscale γ-Al2O3 particles, which originate from native amorphous films on fine Al powders, formed in situ and were homogenously dispersed in the Al matrix. The microstructures of as-extruded and after HIP composites were analyzed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and electron back-scattered diffraction (EBSD). Owing to the presence of nanometric γ-Al2O3 particles with Al high angle grain boundaries (HAGBs), the UFG Al matrix remained stable even after HIP at 600°C for 9h. The mechanical properties and creep performance of composites at testing temperatures of up to 600°C were systematically studied. The Al–Al3Ti composites exhibited a combination of increased strength and Young’s modulus in addition to excellent creep performance and structural stability, which indicates that the studied composites are potential structural materials capable of service at elevated temperatures.

Development of Biodegradable Mg-Ti Alloy Synthesized Using Mechanical Alloying

The aim of this work was to study the effect of milling time on binary magnesium-titanium (Mg-Ti) alloy synthesized by mechanical alloying. A powder mixture of Mg and Ti with the composition of Mg-15wt%Ti was milled in a planetary mill under argon atmosphere using a stainless steel container and balls. Milling process was carried out at 400 rpm for various milling time of 2, 5, 10, 15 and 30 hours. 3% n-heptane solution was added prior to milling process to avoid excessive cold welding of the powder. Then, as-milled powder was compacted under 400 MPa and sintered in a tube furnace at 500 °C in argon flow. The refinement analysis of the x-ray diffraction patterns shows the presence of Mg-Ti solid solution when Mg-Ti powder was mechanically milled for 15 hours and further. Enhancements of Mg-Ti phase formation with a reduction in Mg crystallite size were observed with the increase in milling time. A prolonged milling time has increased the density and hardness of the sintered Mg-Ti alloy.

Reaction synthesis of Ti2AlN MAX-phase

Ti2AlN MAX-phase was synthesized from the powder mixtures of Ti–AlN using the reactionary sintering method. The optimal synthesis mode for the compound containing less than 1 % of TiN impurity phase was determined: isothermal annealing at 1300 °C for 2 hours in argon at a pressure of 3 atm. The preliminary mechanical activation and the reaction synthesis environment were investigated as the factors that can influence the yield of the Ti2AlN phase. It is shown that the activation increases the level of TiN secondary phase. It was also found that the vacuum synthesis does not enable obtaining of single-phase Ti2AlN.

Влияние γ-облучения в малых дозах на структурное состояние механоактивированной смеси порошка состава Ti+Al

Влияние γ-облучения в малых дозах на структурное состояние механоактивированной смеси порошка состава Ti+Al

Effect of rare earth oxide (Y2O3) addition on alloyed layer synthesized on Ti–6Al–4V substrate with Ti+SiC+h-BN mixed precursor by laser surface engineering

In this study, the rare earth oxide (Y2O3) is added to the precursor powder mixture of Ti+SiC+h-BN, and the subsequent mixture is alloyed on the surface of Ti–6Al–4V substrate by laser surface engineering. The XRD spectra indicate that the alloyed layers contain TiN, TiB, Si3N4, Ti5Si3, BN, Ti2N phases in the α-Ti matrix. It is found that the micro-hardness and wear resistance of alloyed layers with Y2O3 addition are higher than those of the alloyed layer without Y2O3 addition in their precursor. The micro-hardness of alloyed layer with Y2O3 addition enhanced from 583HV to 728HV.

Evolution of microstructure and mechanical properties of in situ synthesized TiC–TiB2/CoCrCuFeNi high entropy alloy coatings

The aim of this paper was to explore a one-step in situ method to synthesize the TiC–TiB2 reinforced CoCrCuFeNi high entropy alloy composite coatings. In this method, the composite coatings were prepared by plasma transferred arc cladding process using Ti, B4C, Co, Cr, Cu, Fe, and Ni powder mixture as precursors. The effects of CoCrCuFeNi(Ti, B4C)x (x in molar ratio, 0.1≤x≤0.5) additions on the structure and mechanical properties of the coatings were investigated. For 0.1≤x≤0.2, the coatings induce the formation of face-centered cubic (FCC) and body-centered cubic (BCC) plus TiC structures. Further addition of x content (0.3≤x≤0.5), promotes high volume fraction of dual-phase TiC–TiB2 embedded in FCC and BCC matrix. There are also corresponding variations in mechanical properties with structural evolutions. For CoCrCuFeNi(Ti, B4C)0.1 coating, the nanohardness (H) and Young's modulus (E) are 4.19 and 234GPa, respectively. These properties are further improved as function of x content (H=9.14GPa and E=261GPa are achieved in CoCrCuFeNi(Ti, B4C)0.5 coating). The mechanical hardening is accompanied with an increase of the ratio of hardness to elastic modulus (H/E), the yield pressure (H3/E2) and the elastic recovery (η value). An attempt has been made to co-relate the wear resistance of the coatings with H/E ratio and η value.

FEEDSTOCK FLOW CHARACTERIZATION AND PROCESSING OF POROUS NITI BY METAL INJECTION MOULDING (MIM)

Porous NiTi alloy with a nearly three-dimensionally interconnected pore structure has been successfully fabricated by a transient liquid phase sintering following the metal injection moulding (MIM) process, using a mixture of Ni and Ti elemental powders. The elemental Ni and Ti powders mixture was mixed with a binder system, comprised mainly polyethylene-glycol (PEG) in an alternative technique using a speed mixer, principally incorporating a dual asymmetric centrifuge (DAC). The powder-binder mixture was then characterized using a capillary rheometer at various temperatures and shear rates. It was found that the feedstock exhibited pseudo-plastic behaviour, which is favourable for the MIM process. A temperature range of 120oC - 130oC was considered as the optimum operating condition for the injection moulding processing. The parts were moulded into cylindrical shapes, leached in warm water (60oC for 10 hours), thermally debound in argon and subsequently sintered in a vacuum furnace at four different temperatures ranging from 950oC to 1250oC. All samples underwent expansion in both diameter and height after water leaching and sintering. The XRD results showed that increasing the sintering temperature resulted in a major fraction of the B2 NiTi phase due to phase homogenization and subsequently decreased the amount of secondary phases such as NiTi2 and Ni3Ti. Besides that, the formation of the transient liquid phase during sintering enabled major fraction of pores to be developed with porosity and average size of 39 - 45% and 100 - 120 μm, respectively. The porous parts produced have a great potential to be used as an implant in biomedical applications.

Effect of dispersion method on the deterioration, interfacial interactions and re-agglomeration of carbon nanotubes in titanium metal matrix composites

The influence of various synthesis techniques on the dispersion and evolution of multi-walled carbon nanotubes (MWCNTs) in titanium (Ti) metal matrix composites (TMCs) prepared via powder metallurgy routes has been investigated. The synthesis techniques included sonication, high energy ball milling (HEBM), cold compaction, high temperature vacuum sintering and spark plasma sintering (SPS). Powder mixtures of Ti and MWCNTs (0.5 wt.%) were processed by HEBM in two batches: (i) ball milling of the mixtures (Batch 1) and (ii) ball milling of Ti powder alone, followed by a further ball milling with sonicated MWCNTs (Batch 2). Both batches of the powder mixtures were pressed at 40 MPa into green compacts and then sintered in vacuum. Batch 2 powder mixtures were also consolidated using SPS. The crystallinity and sp2 carbon network of the MWCNTs were characterized through analyzing the characteristic Raman peak ratio (ID/IG) of each processed sample. X-ray diffraction (XRD) was used for phase identification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the morphology of the MWCNTs in the powder mixtures. The evolution of MWCNTs during the fabrication process and mechanical properties of the sintered compacts were discussed in conjunction with the formation of nano-crystalline TiC.

Effects of B4C particle size on pore structures of porous TiB2–TiC by reaction synthesis

Porous TiB2–TiC were prepared by SHS using Ti and B4C powder mixtures. The pores, phase constituents, microstructures and composition distribution of TiB2–TiC were analyzed. The influences of B4C particle size and pressure in green compacts on pore sizes and structures of final products were also discussed. Via combustion front quenching, the reaction process between Ti and B4C particles was achieved. The results showed that the pore size decreased and combination between TiB2 and TiC became closer with the decrease of B4C particle size and increase of pressure. During the reaction, B4C particles decomposed layer by layer, and reacted with the melted Ti to form poor boron phases of TiB and Ti3B4 with needle-like shapes, which existed in quenched samples. With further reacting, TiB and Ti3B4 phases gradually changed to TiB2 with rectangle and hexagonal-plate shapes. The regular TiB2 particles were bound together by TiC, which constructed the skeleton of pores.

Hot extrusion of Be–Ti powder

Be–30.8wt.%Ti powder mixture was extruded in copper and steel containers at 700 and 900°C, respectively. In both cases, achieved extrusion ratio was 7:1.Investigations of microstructure of manufactured Be–Ti rods revealed that processing temperature has a great influence on the metal flow during the extrusion as well as formation of beryllide phases. The results obtained by X-ray diffraction (XRD) analysis proved that brittle intermetallic phases were formed by processing at 900°C; while no evidence of reaction between beryllium and titanium was detected after extrusion at 700°C.Additionally, high-temperature annealing tests of produced Be–Ti samples were performed in order to study the evolution of the phase composition after the heat treatment.The effects of different mechanical properties of core materials (beryllium and titanium) and containers on uniform deformation are discussed in this work.

Microstructure and Mechanical Property of Ti<sub>3</sub>AlC<sub>2</sub>/TiAl<sub>3</sub> Composite Synthesized by Hot Pressing

Ti3AlC2/TiAl3 composite was successfully fabricated by ball milling and in-situ reaction/hot-pressing of Ti, Al and graphite powders mixture at 1200 °C and 30 MPa for 30 min. The phase composition and microstructure of the milled powders and synthesized composite were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), the mechanical properties and the toughening mechanism of 20%vol Ti3AlC2/TiAl3 composite was also studied. The results show that no new phase is detected during 50 h of milling process. The in-situ synthesized samples are fully dense and composed of 72%vol TiAl3, 24%vol Ti3AlC2 and 4%vol Al2O3/TiC. The Vickers Hardness, three-point bending strength and fracture toughness of the composite is ~5.2 GPa, ~243 MPa and ~4.3 MPa/m1/2, respectively. Analysis of microstructure reveals that crack deflection, crack bridging and delamination of Ti3AlC2 are the main mechanism responsible for the toughening.

Microstructure and Mechanical Properties of TiC/Ti<sub>3</sub>AlC<sub>2</sub> <i>In Situ</i> Composites Prepared by Hot Pressing Method

TiC/Ti3AlC2 composites were successfully prepared by hot-pressing sintering method from the elemental powder mixtures of Ti, Al and TiC. A possible reaction mechanism was investigated by XRD. The density, Vickers hardness, flexural strength, and fracture toughness of the TiC/Ti3AlC2 composites were also measured. At 660 °C, Al melted and reacted with Ti to form TiAl3. At 900 °C, TiAl3 reacted with TiC and Ti to form Ti2AlC. At 1100 °C, Ti2AlC reacted with TiC to form Ti3AlC2. Increasing the sintering temperature, the content of Ti3AlC2 increased. The TiC/Ti3AlC2 composites had excellent performance after sintered at 1100 °C, the density, Vickers hardness, flexural strength and fracture toughness of the composite were 4.35 g/cm3, 4.72 GPa, 566 MPa and 6.18 MPa·m1/2, respectively.

Synthesis and characterization of quarternary Ti3Si(1−x)AlxC2 MAX phase materials

Ti3Si(1−x)AlxC2 (x=0–1) quarternary MAX phase materials were prepared by spark plasma sintering of TiC, Ti, Si and Al powder mixtures at 1200°C. Effect of Al addition on lattice parameters, density and hardness were investigated. Impurities are limited to binary phases of TiC and Ti5Si3. No multinary compound other than Ti3Si(1−x)AlxC2 can be detected. TiC exists as impurity in all samples and trace amount of Ti5Si3 can be detected in Samples x=0.1–0.6. Oxidation of Al cannot be avoided although all sintering were performed under vacuum and trace amount of Al2O3 can be found in all samples with Al addition. Experimental results show that the lattice parameters a and c increase linearly with increasing Al content for x=0–1. The lattice variations are strongly anisotropic and follow Vegard׳s law. Both density and hardness decrease as Al content increases. The linear variation of lattice parameters, d spacings of crystalline faces and density against Al concentration suggest that continuous solid solutions of Ti3Si(1−x)AlxC2 (x=0–1) may have been formed between Ti3SiC2 and Ti3AlC2.