Fe-Ti Alloys Research Articles

Magnetic properties of Sm–Fe–Ti nanocomposite magnets with a ThMn12 structure

Sm–Fe–Ti alloys were produced by melt-spinning followed by heat treatment. The rapidly solidified melt-spun ribbons did not contain any hard magnetic ThMn12 phase and thus showed low coercivity. Although no hard magnetic ThMn12 phase was obtained by annealing SmFe12 melt-spun ribbon, annealed SmFe11.5Ti0.5 and SmFe11Ti melt-spun ribbons contained some hard magnetic ThMn12 phase and exhibited high coercivity. The highest coercivity of 0.4MA/m with a remanence of 63.5Am2/kg was achieved in the annealed SmFe11Ti melt-spun ribbon with the soft magnetic α-Fe and hard magnetic ThMn12 phases. The origin of the high coercivity in the annealed SmFe11Ti melt-spun ribbon was found to be the nanosized grains of the α-Fe and ThMn12 phases.

303 メカニカルアロイング法を用いたMg-Al,Ti-Fe系合金創製とその水素親和性(機械材料・材料加工I)

303 メカニカルアロイング法を用いたMg-Al,Ti-Fe系合金創製とその水素親和性(機械材料・材料加工I)

Ti-Fe 合金の微細組織と機械特性に及ぼす Al 添加の影響

Ti-Fe 合金の微細組織と機械特性に及ぼす Al 添加の影響

A Novel Way to Fabricate Fe Doped TiO2 Nanotubes by Anodization of TiFe Alloys

Abstract We reported the fabrication of self–organized, vertically oriented Ti–Fe–O nanotube array films grown by anodization of Ti–xFe alloys in an ethylene glycol and NH4F mixed electrolyte and their Uv–Vis spectrum (200–1000 nm) photoresponse properties. The key factor affecting the morphology is the Fe content. The higher the Fe content is, the flatter the nanotubes surface is, and the more disorder the bottom surface appears. XRD and photoresponse measurements demonstrate the realizable iron doping of the nanotube layers, which leads to a significant visible photoresponse. The Ti–12Fe sample prepared has a high photoresponse in visible range of the spectrum.

Thermodynamic Analysis of Oxide Nucleation in Steel Cooling Process

Nucleating mechanism and controlling methods of Al2O3-TiO2 inclusion formed during steel cooling process is analyzed in this paper. According to the theory of nucleation, only TiO2 could satisfy the critical requirement of homogeneous nucleation to solidify stably when the temperature declines to less than 1863K. Furthermore, the generation of Al2O3 adhering on the surface of solid TiO2 is going to take place through heterogeneous nucleation, and then Al2O3 interacts with TiO2 to form Al2O3-TiO2 complex oxide. There would be no Al2O3-TiO2 complex oxide or much less Al2O3 on condition that the wTi·wO2 is less than 3.96×10-8. Both deeply deoxygenating treatments and controlling the mass of Ti-Fe alloy added into steel are effective means for improving steel quality.

Analysis of the Fe-Ti and Mg-Ti-Fe Alloys Prepared by High Energy Ball Milling and their Hydrogen Capacity

The synthesis and characterizations of Fe-Ti and Mg-Ti-Fe alloys with the atomic ratio of Fe:Ti = 2:1 and Mg:Ti:Fe = 2:5:6 prepared by mechanical alloying technique in toluene solution and measurement the hydrogen absorption properties of the yields have been performed. The Fe-Ti and Mg-Ti-Fe elemental powders are milled with the milling time of 30 h, in a Mixer Mill, type PW 700i high energy ball mill. The milled specimens are analyzed with an X-ray diffractometer, Philip, type PW 1710, using Cu as the anode tube and l = 1.5406 Å. Qualitative and quantitative analyses are determined usingRietveld methoddeveloped by Fuji Izumi. The microstructure of the specimens after milling and hydriding are identified with a scanning electron microscope, Philip type 550. The refinement analysis of the x-ray diffractions results for Fe-Ti alloy shows that before milling the specimen consists of Ti and Fe phases, and after 30 h of milling new phases identified as FeTi and Fe2Ti are formed. In case of Mg-Ti-Fe alloy after 30 h of milling new phases identified as Fe2Ti and FeTi compounds are formed with the absence of Mg-Ti and Mg-Fe. Quantitative analysis of the milled powders shows that the mass fractions of FeTi and Fe2Ti phases are correspondingly 22.5 wt% and is 21.1 wt%, and the rest is Fe. The disappearance of Mg peaks after milling is suggested from the transformation of the crystallite into amorphous state. On hydriding at room temperature, the milled Fe-Ti and Mg-Fe-Ti powders are transformed into b-Ti4FeH8.5, Fe and TiH2. Considering the high hydrogen capacity and the low hydriding temperature of the Mg-Ti-Fe alloy compared to those of Fe-Ti alloy, the Mg-Ti-Fe alloy could be promoted as a new hydrogen storage material.

Surface modification of TiFe hydrogen storage alloy by metal-organic chemical vapour deposition of palladium

TiFe-based hydrogen storage materials are highly sensitive towards gas impurities which induce a significant deterioration of the hydrogen absorption performances. An efficient solution to this problem is in modification of the material surface by the deposition of metals (including Palladium) capable of catalyzing the dissociative chemisorption of hydrogen molecules. In this work the surface modification of TiFe alloy was performed using a metal-organic chemical vapour deposition technique (MOCVD), by the thermal decomposition of palladium (II) acetylacetonate (Pd[acac] 2) mixed with the powder of the parent alloy. Such a treatment was shown to result in the formation of coatings comprised of palladium nanoparticles, which subsequently facilitate the hydrogenation of the material even after its exposure to air, which otherwise prove detrimental. However, the hydrogenation performances were found to be quite sensitive to MOCVD conditions that, most probably, originates from side processes in the interaction of gaseous products of Pd[acac] 2 decomposition with TiFe.

Fabrication of nitrogen trapping test loop for IFMIF-EVEDA

Nitrogen trapping is a key technology for liquid lithium usage, but has not been well investigated in dynamic conditions. Based on IFMIF (International Fusion Material Irradiation Facility)-EVEDA (Engineering Validation Engineering Design Activities), the nitrogen-trapping loop was designed and fabricated at The University of Tokyo. Lithium in the loop can be heated up to 600 °C and is circulated by a mechanical pump. The pump, which works in high temperature lithium, is newly developed as well. Nitrogen trapping material, such as the Fe–Ti alloy pebble, can be installed as a pebble bed column similar to that of the EVEDA nitrogen trap. In order to avoid contamination by air, all of the components are installed in a vacuum vessel or in a vacuum glove box.

Corrosion resistance of Mo–Fe–Ti alloy for overpack in simulating underground environment

In order to examine the application of Mo–Fe–Ti alloy for overpak, the corrosion resistance of heat-treated its alloys was investigated by electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM). The sample subjected to solution heat treatment (ST) had a single β phase and samples subjected to aging heat treatment at 600–700 °C had α phase precipitation in β phase. EIS results showed that the corrosion resistance of the aging heat-treated samples was lower than that of the ST sample, but much higher than that of pure Ti in 10% NaCl solution of pH 0.5 at 97 °C which simulating the crevice solution. Laser micrographs of the aging heat-treated samples indicated that α phase was caused selective dissolution in test solution. The TEM combined with EDAX (energy dispersive X-ray) analyses showed that β phase matrix composed of 2.7 wt.% Mo and 4.8 wt.% Fe, and α phase composed of 0.7 wt.% Mo and 0.1 wt.% Fe in sample aged at 600 °C. Thus, Mo-poor α phase was selectively dissolved in a test solution. In EIS, the ST sample of only β phase showed the highest resistance, and aging heat-treated samples containing α phase (0.7 wt.% Mo) showed higher values than pure Ti in the corrosion test. As Fe was involved in β phase with Mo which increased remarkably the corrosion resistance, the addition of Fe did not decrease the corrosion resistance of aging heat-treated Mo–Fe–Ti alloy in simulating underground environment.

Effect of cooling process on the α phase formation and mechanical properties of sintered Ti–Fe alloys

Titanium sintered compacts can be strengthened by adding iron due to both its high solid solution strengthening effect and its ability to stabilize the bcc β phase. However, these outcomes may be changed by the cooling rate and the amount of iron added, both of which influence the microstructures and properties of the sintered compact. This study presents the sintered properties of Ti– xFe ( x = 3, 5, and 7 wt.%) sintered at 1150 °C under vacuum and then cooled with different cooling schedules. The results indicated that all alloys reached about 96% relative densities. Higher holding temperatures (740 and 640 °C) in the α + β region after sintering increased the tensile strength and hardness due to the higher amounts of the β phase and the acicular α precipitates inside the β. With holding at a lower temperature of 550 °C, the amount of β phase decreases and no secondary α precipitates were observed in the β phase. No TiFe compound was observed in any of the sintered parts, even with a slow cooling rate, indicating that iron is a very strong β phase stabilizer that can suppress the eutectoid reaction at 595 °C. These changes in microstructure result in significant changes in mechanical properties.

Direct Production of Ti–Fe Alloy in Liquid by Electrowinning in Molten Slag

Aiming at the direct production of Ti–Fe alloy, its direct electrowinning has been attempted in a CaF2–CaO–TiO2–FeO bath by using a direct-current electro-slag remelting unit. The experiments were carried out in the slag where the molar ratio of CaO to TiO2 was fixed as 1.5, and the influence of the molar ratio of FeO to TiO2 was mainly investigated. The experimental results proved that Ti–Fe alloy in liquid could be obtained at the limiting bath compositional range. At the molar ratio of FeO to TiO2 was 0.90, both the Ti content in the deposit and the cathodic current efficiency were the best under the conditions in this study; the Ti content reached about 50 wt%, and the cathodic current efficiency also did about 50% at best.

Experimental investigation on the formation mechanism of the TiFe alloy by the molten-salt electrolytic titanium concentrate

The ferrotitanium alloy was prepared in the molten CaCl2 system, in which resolidified ilmenite and the graphite crucible were used as cathode and anode. In this study, the electrolytic voltage was fixed at 3.1V, and three different temperatures were applied: 850oC, 875oC and 900?C. Finally, the product was examined by SEM and XRD to determine the phase transformation after the electrolysis. The results show that the ilmenite was firstly reduced to Fe, and finally the TiFe alloy was formed. The intermediate products include CaTiO3, TiO2, Ti2O3, TiO, Fe, TiFe2, and Ti. Different product and structure can be obtained by changing temperature. According to thermodynamic calculation, the principal electroreduction products are Ti and TiFe2 and then Ti and TiFe2 are formed by interdiffusion which is governed by temperature.

Deoxidization mechanism of preparation FeTi alloy using ilmenite concentrate

An investigation into the deoxidization mechanism of the electrochemical reduction of ilmenite concentrate to FeTi alloy in molten calcium chloride has been performed. The results show that deoxidization proceeds through a number of individual stages some of which involve reduction of iron, formation and desposition of calcium titanates(CaTiO3), reduction of the various low value titanium oxides and formation of Fe2Ti and FeTi. CaTiO3 is formed because Ca2+ contained in electrolyte take part in the deoxidization process.

Anisotropic mechanical behavior of ultrafine eutectic TiFe cast under non-equilibrium conditions

The effect of solidification conditions on microstructural and mechanical properties of eutectic TiFe alloy cast under different conditions was examined. Samples exhibit different ultrafine eutectic structures (β-Ti(Fe) solid solution + TiFe). Different cooling conditions lead to the evolution of ultrafine eutectic oval-shaped colonies or elongated lamellar colonies with preferred orientation. Isotropic as well as anisotropic mechanical properties were obtained. Alloys exhibit compressive strengths between 2200 and 2700 MPa and plastic strains between 7 and 19 pct. in compression.

Enhancement of fatigue life of Ni–Ti–Fe shape memory alloys by thermal cycling

The effect of thermal cycling on the load-controlled tension–tension fatigue behavior of a Ni–Ti–Fe shape memory alloy (SMA) at room temperature was studied. Considerable strain accumulation was observed to occur in this alloy under both quasi-static and cyclic loading conditions. Though, in all cases, steady-state is reached within the first 50–100 cycles, the accumulated steady-state strain, ɛ p,ss, is much smaller in thermally cycled alloy. As a result, the fatigue performance of them was found to be significantly enhanced vis-a-vis the as-solutionized alloy. Furthermore, under load-controlled conditions, the fatigue life of Ni–Ti–Fe alloys was found to be exclusively dependent on ɛ p,ss. Observations made by profilometry and differential scanning calorimetry (DSC) indicate that the 200–500% enhancement in fatigue life of thermally cycled alloy is due to the homogeneous distribution of the accumulated fatigue strain.

Microstructure and room temperature mechanical properties of hot-pressed Nb–Si–Ti–Fe alloys

Bulk alloys were fabricated by uniaxial hot pressing from ball milled Nb-Si–Ti–Fe powder mixtures with the fixed Si content (16 at.%) and various compositions of Ti and Fe, and the effects of Ti and/or Fe on the ball milling, microstructure and room temperature mechanical properties of the materials were investigated. It was revealed that the Ti addition inhibited the ball milling process with the same milling parameters. For the hot-pressed alloys, Nb 4FeSi phase was detected in the alloys containing Fe, and Fe mainly dissolved into niobium silicides from the result of elemental mapping. The solubility of Si in Nbss was enhanced by the addition of Ti, and Nb 3Si expected was not observed in the Ti-bearing alloys that may be due to the lower Ti content in the reaction zone between the particles. The Ti-added alloys hot pressed from a shorter time showed the coarser microstructure with Nbss in the shape of narrow strip distributed in river pattern, while near-equiaxed macrostructure was obtained in the Nb–Si–Fe alloys. The improvement in both room temperature fracture toughness and flexural strength was achieved in Ti-added alloys. The toughening and strengthening mechanisms were discussed from the ductile-phase toughening of crack bridging and solid solution strengthening, respectively.

High Temperature Electrolysis of Ti and its Alloys with a DC-ESR Unit

Direct electrolysis of Ti and its alloys has been attempted by the process using a DC-ESR unit. The concept of the process is explained in detail, and the expected key issues are commented. Liquid Ti metal was obtained in a CaF2-CaO-TiO2 bath, and electrolysis by using a new type of the electrolytic cell was also tried. Ti-Al alloy was successfully deposited in a CaF2-CaO-TiO2-Al2O3 bath, whereas Ti-Si alloy was not obtained in a CaF2-CaO-TiO2-SiO2 bath yet. Ti-Fe alloy was extracted in CaF2-CaO-TiO2-FeO bath of a particular composition. A common correlation between the cathodic current efficiency and the average consumed electric power seen in the Ti, Ti-Al and Ti-Fe electrolysis suggested the importance of sufficient temperature in the process. The bath composition also affected the temperature through the change in the electric conductivity of the bath.

Structure and mechanical properties of an AlCr6Fe2Ti1 alloy produced by rapid solidification powder metallurgy method

Abstract In the present paper, the structure and properties of a Al–Cr–Fe–Ti alloy produced by powder metallurgy are described. An initial rapidly solidified powder alloy was prepared by the pressure nitrogen melt atomisation. Subsequently, the granulometric powder fraction of less than 45 μm was hot-extruded. According to X-ray diffraction and transmission electron microscopy observation, the compact material is composed of α-Al grains and spheroids of intermetallic phases. The α-Al grains of the compacted material are recrystallized and neither residual stress nor texture were observed. The values of ultimate tensile strength and yield strength of the investigated material were similar to the values for conventional Al-based alloys. Dependences of ultimate tensile strength and yield strength on temperature were also measured. Excellent thermal stability of the powder metallurgy produced Al–Cr-based material was proven by room-temperature hardness measurement after long-term annealing at elevated temperature.

Magnetostriction of Fe-Ti Alloys

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Longitudinal and transverse magnetostriction measurements were performed on polycrystalline Fe<formula formulatype="inline"><tex Notation="TeX">$_{100 - {\rm x}}$</tex></formula>Ti<formula formulatype="inline"><tex Notation="TeX">$_{\rm x}$</tex></formula> alloys, for a large Ti concentration range, from <formula formulatype="inline"><tex Notation="TeX">${\rm x} = $</tex></formula> 8.8 to 34.7 at.%. Our results showed that substituting Fe by Ti does not significantly enhance the magnetostriction. For all Ti concentrations in the magnetically saturated state, the longitudinal magnetostriction values vary from <formula formulatype="inline"><tex Notation="TeX">${-}2 \times 10^{- 6}$</tex></formula> to <formula formulatype="inline"><tex Notation="TeX">$6 \times 10^{- 6}$</tex></formula>. On the other hand, Fe<formula formulatype="inline"><tex Notation="TeX">$_{100 - {\rm x}}$</tex></formula>Ti<formula formulatype="inline"><tex Notation="TeX">$_{\rm x}$</tex></formula> alloys exhibit a large forced volume magnetostriction, which increases with increasing Ti-concentration. The magnetostriction behavior could be explained considering investigations of the hyteresis loops and the microstructure . </para>

Hydrogen storage in binary and ternary Mg-based alloys: A comprehensive experimental study

This study focused on hydrogen sorption properties of 1.5 μm thick Mg-based films with Al, Fe and Ti as alloying elements. The binary alloys are used to establish as baseline case for the ternary Mg–Al–Ti, Mg–Fe–Ti and Mg–Al–Fe compositions. We show that the ternary alloys in particular display remarkable sorption behavior: at 200 °C the films are capable of absorbing 4–6 wt% hydrogen in seconds, and desorbing in minutes. Furthermore, this sorption behavior is stable over cycling for the Mg–Al–Ti and Mg–Fe–Ti alloys. Even after 100 absorption/desorption cycles, no degradation in capacity or kinetics is observed. For Mg–Al–Fe, the properties are clearly worse compared to the other ternary combinations. These differences are explained by considering the properties of all the different phases present during cycling in terms of their hydrogen affinity and catalytic activity. Based on these considerations, some general design principles for Mg-based hydrogen storage alloys are suggested.