Mechanical Alloying Of Ti Research Articles

Preparation of TiC/Ti₃SiC₂ Composite by Sintering Mechanical Alloyed Ti-Si-C Powder Mixtures.

The present work aims to evaluate the crystalline phases and microstructure of a TiC-Ti₃SiC₂ ceramic composite, obtained by mechanical alloying of Ti, C and Si powders and subsequent sintering. A mechanical alloying technique in a planetary ball mill for 1, 10, 50, 100 and 200 h using Ti, Si and C powders with molar ratios of 3:1:2 as feedstock in argon (Ar) gas was employed to prepare nano-sized Ti-Si-C powders. TiC crystallite size and lattice strain were evaluated by X-ray diffraction analysis (XRD) and the morphological characteristics and particle size distribution were examined using scanning electron microscope (SEM). After milling, a reduction of the average particle size and crystallinity is observed. Furthermore, after 10 h of milling time, TiC starts to crystallize. The powder mixture obtained after 200 h of milling was compacted and sintered at 1200 °C under controlled atmosphere, for 15 min, 2 h or 4 h with a heating rate of 5 °C/min. Almost full densification of samples sintered for 2 h and 4 h has been achieved, with relative densities close to 98.8±0.2% and TiC and Ti₃SiC₂ as crystalline phases with an average crystallite size of TiC near 0.7 μm. Rietveld refinement indicates that the majority TiC-cubic phase (>85 vol%) presents a unit cell volume of 8.03 nm³ after sintering at 1200 °C. Despite the maintenance of the volume of the hexagonal unit cell of Ti₃SiC₂, (15.05 nm³), the increase of the isothermal sintering time resulted in an increase of the lattice parameter "a", from 0.315 nm to 0.320 nm, and a reduction of the lattice parameter "c" from 1.750 nm to 1.705 nm. The control of the changes in the residual stresses within the TiC matrix and the Ti₃SiC₂ precipitates, which is associated with the deformation in the lattice parameters, must be controlled to achieve high fracture toughness in the composite.

Improvement in the mechanical and tribological behavior of epoxy matrix with the inclusion of synthesized Ti3AlC2 MAX particles

This study has investigated the mechanical and tribological performance of epoxy composites filled with different contents of Ti3AlC2 MAX phase particles. The Ti3AlC2 particles were synthesized by the mechanical alloying of Ti, Al and C powders. The ultrasonic blending was used for preparing the mixture of Ti3AlC2 and epoxy matrix. The Vickers microhardness and pin on disc tests were carried out to investigate the mechanical and wear properties of samples, respectively. Moreover, the fracture and worn surface of the samples were analyzed by scanning electron microscopy images. Results showed that the microhardness values were increased due to increasing the content of Ti3AlC2 in the epoxy matrix. In this regard, the highest value of 39.24 Hv was achieved for composites containing 0.75 wt.% Ti3AlC2, which corresponds to the 75.4% improvement in microhardness value, compared to neat epoxy. Moreover, wear results demonstrated that the friction coefficient and wear rate values were decreased by the addition of Ti3AlC2 particles in the epoxy matrix.

In-situ synthesis of Ti-Fe-based alloys prepared by the combination of mechanical alloying and laser melting deposition: Microstructure and corrosion resistance

The Ti-Fe-based alloys were in-situ synthesized by the combination of mechanical alloying and laser melting deposition (LMD). The microstructure evolution and corrosion behaviors of Ti50Fe50 and Ti40Fe50Cu10 alloys were also investigated. The results show that mechanical alloying of Ti and Fe elemental mixtures induces the formation of intermetallic TiFe, Ti-rich amorphous phase and α-Fe(Ti) solid solution and that the addition of Cu can refine the size of nanocrystalline TiFe phase. Although LMD-produced Ti50Fe50 and Ti40Fe50Cu10 alloys are composed of TiO dendrites and α-Fe/TiFe2 (hexagonal MgZn2-type Laves structure) eutectic, the addition of Cu can refine the TiO dendrites, induce the formation of TiO2 particles and dissolve into the TiFe2 phase in the Ti40Fe50Cu10 alloy. As a result, the LMD-produced Ti40Fe50Cu10 alloy exhibits higher corrosion resistance than the LMD-produced Ti50Fe50 alloy.

Effect of Ni Contents on Microstructures and Mechanical Properties for (Ti<sub>0.8</sub>Mo<sub>0.2</sub>)C-Ni Cermets

The (Ti0.8Mo0.2)C-xNi cermets (x = 10, 20, 30 and 40mass%) were prepared by two milling processes; first, the (Ti0.8Mo0.2)C produced by mechanical alloying of Ti, Mo and C powders (Process I). Second, mechanical alloyed (Ti0.8Mo0.2)C and commercial Ni powders mixed by tumbling ball milling (Process II) for 72 h. On (Ti0.8Mo0.2)C-40Ni, the milling time of Process II was 96 h in addition of 72 h. The Vickers hardness with fracture toughness and the quantitative microstructural parameters were measured and analyzed. The relationship between fracture toughness and hardness for the cermets was on the fitted curve derived from the previous data for the cermets, except for the case of (Ti0.8Mo0.2)C-40Ni for 72 h, which is lower fracture toughness than that for the previous works and (Ti0.8Mo0.2)C-40Ni for 96 h. The contiguity of the samples tend to increase with increasing hard phase contents except for the case of (Ti0.8Mo0.2)C-40Ni for 72 h, which is higher than those of (Ti0.8Mo0.2)C-40Ni for 96 h. On the other hand, the coefficient of variation for hard phase of the both (Ti0.8Mo0.2)C-40Ni were almost same. [doi:10.2320/matertrans.M2014087]

Effect of severe mechanical alloying on the microstructure parameters of 3Ti + Al mechanocomposites

The microstructure of mechanocomposites produced by mechanical alloying of Ti and Al powder mixtures in high-energy planetary ball mill has been studied by the methods of transmission electron microscopy and X-ray diffraction analysis. The formation of highly defect structural states with high magnitudes of the crystal-lattice curvature and large density of disclinations at the boundaries of submicrocrystals and nanocrystals has been revealed. It is assumed that such a highly defect structural state is an important channel for the accumulation of deformation energy upon mechanical alloying and plays an essential role in phenomena of increasing reactivity of components of mixture systems, abnormal mass transfer, and solid-state interaction of reactants.

Formation of Ti3AlC2 by mechanically induced self-propagating reaction in Ti–Al–C system at room temperature

The formation of Ti3AlC2 was first investigated by mechanically induced self-propagating reaction (MSR) in Ti–Al–C system at room temperature. The effects of the milling parameters on the formation of Ti3AlC2 were discussed. The phase composition and microstructure were analysed and observed by using X-ray diffraction and scanning electron microscopy, respectively. The formation mechanism of Ti3AlC2 was analysed. An MSR was ignited during mechanical alloying of Ti, Al and C powders after a short time. An exothermic reaction between Ti and Al in the Ti–Al–C system first occurred after a certain milling time. Then, Ti–C reaction was induced at high temperature. All of the above reactions were exothermic that resulted in Ti–Al liquid formation. The previously formed TiC dissolved into and nucleated in the Ti–Al liquid. At last, Ti3AlC2 formed between the Ti–Al melt and the TiC. The final products consist of Ti3AlC2, TiC and Al3Ti.

Fabrication of TiC-20 mass%Ni Cermet Using MA-PCS Process

Mechanical alloying and pulsed-current sintering were used to synthesize TiC-20 mass%Ni cermet with ultra-fine TiC particles dispersed. The mixture, in which Ti and Ni elements were uniformly distributed, was prepared by mechanical alloying of Ti, Ni and graphite powders for 18 ks. TiC particles were produced in the mixture milled for longer than 18 ks through a combustion synthesis reaction during heating. Mechanically alloyed Ti-C-Ni composite powder milled for 18 ks was consolidated using pulsed-current sintering at 1223 K under 70 MPa pressure. The sintered compact consisted of TiC and Ni. The average grain size of TiC particles in the sintered body was 0.80 mm. The relative density of the sintered compact reached 92% of the theoretical one; its Vickers hardness was 2260 Hv.

Effect of Properties of Titanium Aluminide Powders and Detonation Spraying Conditions on Phase and Structure Formation in Coatings

We have studied phase formation in detonation coatings sprayed from Ti - 50 at.% Al powders. The powders of the alloy were obtained by various methods: crushing an ingot and mechanical alloying of Ti and Al. Using polyphase nanostructural materials activated by mechanical alloying makes the process of phase formation in the gas-thermal sprayed coatings based on them more general-purpose and controlled due to the more active and more subtle reaction of the material with the gaseous atmosphere. We have shown that from mechanically alloyed Ti - 50 at.% Al powder, using the detonation-gas spraying method we can consolidate a coating based on Al2TiO5 by oxidizing action of the working gas on the powder and also a coating based on titanium aluminides with TiN inclusions by nitriding action. The phase composition of the cast microstructural γ-TiAl powder is inherited by the coating.

Rapid synthesis of Ti alloy with B addition by spark plasma sintering

Abstract The in situ TiB/Ti–4.0Fe–7.3Mo composites were fabricated by plasma spark sintering (SPS) technique using mechanical alloying of Ti, Fe65Mo and B powder. The effects of sintering temperature on densification of the composites and microstructure of the in situ synthesized TiB were investigated using scanning electron microscope (SEM) and transmission electron microscope (TEM). A dense composite was obtained after sintering at 1000 °C for 5 min. Under proper ball milling and SPS conditions in situ TiB reinforced Ti–4.0Fe–7.3Mo composites have been prepared. The in situ TiB showed a typical needle shape grow along [0 1 0] direction. The transverse cross-section of TiB grain is a hexagonal shape with the planes of (1 0 0), (1 0 1) and ( 1 0 1 ¯ ) . The stacking faults in the (1 0 0) plane were observed in the TiB needles.

メカニカルアロイング法により作製したＴｉＦｅ水素吸蔵合金の初期活性化特性

The intermetallic TiFe alloy is a hydrogen storage alloy with a high hydrogen storage capacity, 1.8wt%, and a relatively low cost compared with other alloys. However, the TiFe alloy does not easily start to absorb hydrogen because of the presence of a very stable oxide layers covering the alloy surface. In order to activate the alloy, the alloy needs an intensive initial activation process at high temperatures over 720K under high hydrogen pressures over 6.5MPa. In this study, the intermetallic TiFe alloy was successfully prepared by mechanical alloying of Ti and Fe metals. The formed nano-TiFe alloy with a mixture of nano and amorphous structures was found to have a very easy, activation behavior compared with a standard polycrystalline TiFe alloy.

Synthesis of Quasicrystal Phases by Mechanical Alloying of Ti45+xZr38-XNi17 (-4≤ X ≤16) Powder Mixtures, and Their Hydrogen Storage Properties

ABSTRACTMechanical alloying of Ti45+xZr38-xNi17 (-4 ≤ x ≤ 16) elemental powder mixtures leads to the formation the amorphous phase, but subsequent annealing at 833 K causes the formation of icosahedral (i) quasicrystal and the Ti2Ni-type crystal phases. The α-Ti phase is also produced in Ti-rich powders after annealing. Both the quasilattice constant of the i-phase and the lattice parameter of the Ti2Ni-type crystal phase decrease monotonically with increasing substituted amount of Ti because of the smaller radius of the Ti atom. The maximum hydrogen concentration in the i-phase in all powder compacts, after electrochemical hydrogenation in a KOH solution, is almost the same, about 63 at% ([H] / [M] ≈ 1.7). The onset temperature of hydrogen desorption is about 570 K (at a heating rate of 5 K/min) for all powders, but the temperature for the maximum hydrogen desorption rate increases with increasing Ti concentration in the powders, suggesting that some hydrogen atoms might be more strongly bound in the quasilattice where the original Zr sites become occupied by Ti atoms.

Local structure of deuterated Ti-Zr alloy

The Ti–Zr alloy system is isomorphous over the total concentration range. A neutron zero-scattering alloy can be obtained at the composition Ti0.676Zr0.324 because of negative and positive coherent neutron scattering amplitudes of Ti and Zr respectively. A (Ti0.676Zr0.324)D0.31 amorphous alloy was synthesized by mechanical alloying (MA) under a deuterium-gas atmosphere of 0.08 MPa. In contrast, it is found that the MA of Ti and Zr powders under a deuterium-gas atmosphere of 2.0 MPa forms a nano-crystalline (Ti0.676Zr0.324)D1.54 alloy, which is composed of TiH2 and ZrH2 crystalline compounds.

Investigation of mechanical alloying of Ti–Al compounds using perturbed γγ-angular correlation spectroscopy, x-ray diffraction, and differential scanning calorimetry

Ti0.50Al0.50 and Ti0.75Al0.25 compounds were mechanically alloyed by ball milling of elemental Ti and Al powders. Radioactive 111In atoms incorporated into these compounds were used to investigate the different locally ordered crystalline structures by perturbed γγ-angular correlation spectroscopy (PAC). The formation of the intermetallic compounds γ–TiAl and α2–Ti3Al was observed on an atomic scale and occurred as a consequence of the heat treatment of mechanically alloyed Ti0.50Al0.50 and Ti0.75Al0.25, respectively. Due to the sensitivity of PAC to local order on an atomic scale, information about formation conditions and thermal stability of a new metastable phase with an ordered tetragonal crystal structure is presented for Ti0.50Al0.50 samples. In addition, the formation of the ordered phase Ti2AlN was observed, indicating the incorporation of N during the milling process. The PAC investigations were complemented by x-ray diffraction and differential scanning calorimetry measurements.

Synthesis of amorphous and quasicrystal phases by mechanical alloying of Ti 45 Zr 38 Ni 17 powder mixtures, and their hydrogenation

Mechanical alloying of Ti 45 Zr 38 Ni 17 powder mixture forms an amorphous phase, but subsequent annealing causes the formation of an icosahedral ( i ) phase. The maximum hydrogen concentration that can be loaded at 573K at a hydrogen pressure of 3.8MPa is the same (\\[H]/\\[M] 1.5) for the amorphous and i -phase powders. With hydrogenation, the i -phase is almost stable, forming no hydrides, whereas the amorphous phase transforms to a fcc hydride. The activation energy for hydrogen desorption for the i -phase is about 127kJmol -1, which is lower than that for the amorphous phase, suggesting that the i -phase powder may have better properties for hydrogen-storage applications.

Mechanical milling of fullerene with carbide forming elements

Mechanical alloying of Ti, V, Cr, Mo and W with fullerene (C60(C70)) and graphite reveals that fullerene is more reactive than graphite. The formation heat of carbide is the driving force for reaction in the mechanical alloying process. Higher heat of formation results in the direct formation of carbide in Ti-C systems, and the formation of carbide in V-C systems during the subsequent heating of milled powder. In the systemsc with lower carbide heat of formation, a mixture of metal with carbon is obtained by ball milling. No carbide was obtained even after heating the milled powders up to 973 K. Small amount of fullerene remained when milled with Mo and W for 10 hours.

Mechanical activation of the reactive sintering of titanium carbide

This paper describes the mechanical alloying of Ti and C powders by intensive grinding in a planetary mill. The effect of milling conditions and initial composition on the compositional homogeneity and properties of powders and samples consolidated by hot-pressing was studied by x-ray diffraction, scanning electron microscopy, and surface area measurement. The diffraction patterns indicated that a powder mixture ground for 24 hours transforms to TiC after sintering for only one minute at 600°C under a pressure of 3 GPa.

Thermodynamic Calculation of Phase Equilibria in the Ti–Co and Ni–Sn Systems

A thermodynamic model for the titanium-cobalt system has been developed utilizing measured enthalpies of mixing of the liquid and evaluated phase-diagram data. The free energies of the liquid, bcc, fcc, and hcp solid solutions, and TiCo, Ti2Co, TiCo2, and TiCo3 compounds were calculated for a temperature of 400 K. The model and measured heats of crystallization have been used to predict the free energy of the metastable amorphous phase at 400 K, needed for comparison with experimental results on the mechanical alloying of Ti and Co. The predicted glass-forming range for alloys prepared by mechanical alloying is from 10 to 81.5 at. % Co. We adopted a similar approach for modeling the Ni–Sn system to calculate the free energies of Ni3Sn, and Ni3Sn2, and the liquid (amorphous) and fcc solid solutions in the nickel-rich region at 240 K. In this system the inclusion of the magnetic contribution to the free energy of the Ni-rich fcc solid solution is important in interpreting the results of mechanical alloying. We propose a simple transformation of the free-energy curves, which assists in the graphical identification of the glass-forming ranges.

Mechanical Alloying of Ti50Al50Powders and Their Consolidated Properties

Abstract Elemental powder mixtures of 50Ti-50Al (at.%) were mechanically alloyed via various ball milling methods. The microstructural evolution during the milling indicates that the mechanical alloying behavior is strongly affected by milling methods, and horizontal ball milling is most effective for producing homogeneous metastable powders. The mechanically alloyed powders were consolidated by vacuum hot pressing followed by homogeneous annealing. Compression testing results showed that the annealed specimens still retain fine grains and have a good combination of fracture strength and ductility, as compared to cast specimens of the same alloy.

Mechanical Alloying of Ti–Al Powder Mixtures under Nitrogen Atmosphere

Elemental titanium powder and Ti100−xAlx elemental powder mixtures were milled in a vibrational ball mill, Spex 8000, under nitrogen atmosphere, and the nitrogen absorption behavior during milling and the structures of milled powders were examined by means of X-ray diffraction measurements, SEM and HRTEM observations. The titanium powder absorbed 50 at% of nitrogen during milling and was nitrided completely to form TiN. The Ti–Al powder mixtures with compositions X≤50 absorbed also about 50 at% of nitrogen and were nitrided completely to form a solid solution nitride (Ti, Al)N with the NaCl-type structure through an amorphous-like solid solution. Each of the TiN and (Ti, Al)N powder particles had a nanocrystalline structure consisting of about 5 nm size grains. In the case of the Ti100−xAlx powder mixtures with compositions 60≤X≤70, 35-15 at% of nitrogen were absorbed in the powders and each of the milled powders had a dual-phase structure consisting of about 5 nm size (Ti, Al)N and Al–Ti solid solution phases. The Ti–Al powder mixtures with compositions 80≤X≤100 scarcely absorbed nitrogen and therefore no nitrides formed. The main reason why the aluminum rich Al–Ti powder mixtures scarecely absorb nitrogen may be ascribed to the fact that aluminum powder is too soft to be-refined by milling.

Amorphisation and phase transformations in mechanically alloyed Ti–Al powders: electron microscopy investigation

The microstructural evolution during mechanical alloying of Ti and Al powders has been investigated by X-ray diffraction, scanning electron microscopy (SEM)–energy dispersive spectroscopy, and transmission electron microscopy (TEM). Observations by SEM showed a progressive change of the powders' morphology as a function of milling time. Observations by TEM, performed on a sample milled for 20 h, revealed the simultaneous occurrence of amorphous zones and nanocrystalline domains. The observed amorphous phase is not the final milling product. After 34 h of milling it was possible to identify by TEM fcc (a=0·41 nm) nanocrystalline zones, with a mean size of about 10 nm. By irradiating the powder milled for 20 h with high density electron beams, a sudden in situ crystallisation took place. The crystallite (fcc with a=0·41 nm) size was between 0·1 and 0·5 μm.MST/1281