• Korean Journal of Materials Research
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• v.22 no.11
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• pp.615-619
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• 2012

Recently, ultrafine grained (ufg, typically 100 > d > 500 nm) Ti-Fe eutectic materials have been highlighted due to their extraordinarily high strength and good abrasion resistance compared to conventional coarse grained (cg, d > $1{\mu}m$) materials. However, these materials exhibit limited plastic strain and toughness during room temperature deformation due to highly localized shear strain. Several approaches have been extensively studied to overcome such drawbacks, such as the addition of minor elements (Sn, Nb, Co, etc.). In this paper, we have investigated the influence of the addition of Gd and Y contents (0.3-1.0 at.%) into the binary Ti-Fe eutectic alloy. Gd and Y are chosen due to their immiscibility with Ti. Microstructural investigation reveals that the Gd phase forms in the eutectic matrix and the Gd phase size increases with increasing Gd content. The improvement of the mechanical properties is possibly correlated to the precipitation hardening. On the other hand, in the case of Ti-Fe-Y alloys, with increasing Y contents, primary phases form and lamellar spacing increases compared to the case of the eutectic alloy. Investigation of the mechanical properties reveals that the plasticity of the Ti-Fe-Y alloys is gradually improved, without a reduction of strength. These results suggest that the enhancement of the mechanical properties is closely related to the formation of the primary phase.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.5
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• pp.303-310
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• 2023

β titanium alloys are widely used in aerospace industry due to their excellent specific strength and corrosion resistance. In particular, mechanical properties of metastable β titanium can efficiently be controlled by various deformation mechanisms such as slip, twinning, and SIM (Stress-Induced Martensite Transformation), making it an ideal material for many industrial applications. In this study, Ti-5Mo-xFe (x=1, 2, 4 wt%) alloy was designed by adding a relatively inexpensive β element to ensure price competitiveness. Additionally, microstructural analysis was conducted using OM, SEM, and XRD, while mechanical properties were evaluated through hardness and compression tests to consider the deformation mechanisms based on the Fe content. SIMT occurred in all three alloys and was influenced by the presence of β_m (metastable beta) and beta stability. As the Fe content decreased, the α'' phase increased due to SIMT occurring within the β_m phase, resulting in softening. Conversely, as the Fe content increased, the strength of the alloy increased due to a reduction in α'' formation and the contributions of solid solution strengthening and grain strengthening. Moreover, unlike the other alloys, shear bands were observed only in the fracture of the Ti-5Mo-4Fe alloy, which was attributed to differences in texture and microstructure.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.4
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• pp.135-141
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• 1998

The effects of heat-treatment on discharge characteristics of $TiFe_{1-x}Ni_x$ alloy were investigated. The content of Ni in alloy was varied from x = 0.1 to 0.6 by each 0.1 increment. Discharge capacity change of each alloy with C/D cycles was measured. With increasing Ni-content initial discharge capacity was increased. but at x = 0.6 it was deceased again. With increasing C/D cycles discharge capacity was rapidly decreased in the alloy of high Ni-content. In order to investigate the effects of heat-treatment on cycle life, $TiFe_{0.5}Ni_{0.5}$ alloy having maximum initial discharge capacity was heat-treated at various temperatures in the range of $700{\sim}900^{\circ}C$ and tested. The loss of initial discharge capacity was appeared at all temperatures. but cycle characteristics of the alloy was improved. The electrodes heat-treated for 1 hour in the range of $700{\sim}850^{\circ}C$ showed good recovery of discharge capacities through repeated cycles, and from SEM observation results these were considered as 1 hour in the range of $700{\sim}850^{\circ}C$ showed good recovery of discharge capacities through repeated cycles, and from SEM observation results these were considered asbeing due to increased electrode strength and small loss of porosity during heat-treatment. The electrode heat-treated for 1 hour at $900^{\circ}C$ showed poor discharge characteristics because of low porosity.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.6
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• pp.264-271
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• 2016

The effect of the oxygen content and the annealing temperature on the tensile behavior of the Ti-1.5Al-3Fe-0.25Si-(0.1~0.5)O alloy was investigated. The tensile properties were dependent on the volume fraction of the microstructure constituents, i.e. the equixed ${\alpha}$, equixed ${\beta}$ and lamellar ${\alpha}$. The results showed that the O-partitioned equixed ${\alpha}$ had a much higher strength compared to the equixed ${\beta}$. The strength of the lamellar ${\alpha}$ increased with increasing the annealing temperature because the O content of the lamellar ${\alpha}$ increased. Ti-1.5Al-3Fe-0.25Si-0.3O alloy annealed to $900^{\circ}C$ where the volume fraction of lamellar ${\alpha}$ was the highest exhibited an excellent combination of the strength (1198.5 MPa) and ductility (27.5%). The effect of the lamellar ${\alpha}$ on the ductility was discussed.

• Membrane Journal
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• v.25 no.2
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• pp.191-201
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• 2015

We have studied on the preparation of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloy, the characteristics of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloy by X-ray diffractometer (XRD), pressure composition temperature (PCT) curve, scanning electron microscopy (SEM) and the $H_2-N_2$ gas mixture separation of $TiCo_xFe_{1-x}$(x=0.50~1.00)- stainless steel (SS) composite membranes. The formation of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloys with cubic crystal same as TiCo was confirmed by X-ray diffractometer. $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloys showed the hysteresis at $120^{\circ}C$. As the Fe content of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloys increased, the hysteresis was increased both range x=0.90~1.00 and x=0.55~0.60, and the range x=0.55~0.90 gave decreased hysteresis. $TiCo_{0.55}Fe_{0.45}$ alloy was the one showed the lowest hysteresis among them. The lowest value of hydrogen permeation pressure of $TiCo_xFe_{1-x}$(x=0.50~1.00)-SS composite membrane was $TiCo_{0.55}Fe_{0.45}$-SS composite membrane with the value of 2.5 atm at $120^{\circ}C$; otherwise, $TiCo_{0.90}Fe_{0.10}$-SS composite had the highest pressure value among the membranes with the value of 10 atm. $TiCo_{0.55}Fe_{0.45}$-SS composite membrane was the best to separate the $H_2-N_2$ gas mixture excellently among the $TiCo_xFe_{1-x}$(x=0.50~1.00)-SS composite membranes since $TiCo_{0.55}Fe_{0.45}$ had the least hysteresis, and hydrogen permeation pressure was the lowest with value of 2.5 atm.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.71-75
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• 2022

In this research, Fe-Ni alloy films were electrodeposited on stainless steel (SS304 and SS430) and Ti plates to investigate the effects of surface conditions of cathode on deposits. The Ti plates were electropolished in 3 M H₂SO₄-methanol electrolytes at various conditions before electrodeposition, and unpolished Ti and the optimized specimen, polished at 10 V for 8 min, were used as cathode. The anomalous codeposition, the phenomenon which more active Fe is reduced preferentially, occurred on all substrate, however, there were differences in composition of all deposits. As the results of potential monitoring during electrodeposition, it was confirmed that the larger overpotential was applied to the deposition cell when using Ti cathode, leading to high Fe content of deposits from unpolished Ti due to increase in nucleation of Fe. Also, it was founded that the polished Ti can reduced deposition overpotential.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.153.2-158
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• 1999

A study has been made to investigate how the fomability of Ti-10V-2Fe-3Al alloy is related to the initial microstructure and process variables such as temperature and strain rate. It has been found that the deformation resistance at high temperature is increased with the increase in the thickness of grain boundary a (GB)a and/or acicular a phase and however the effect of a morphology on the hot formability is considered insignificant due to the breakage of GB a and/or acicular a into several equiaxed a particles

• Journal of Korea Foundry Society
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• v.35 no.5
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• pp.120-127
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• 2015

The effects of Ti, B and Zr on grain refinement and castability were investigated in Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurement of cooling curve and micro-structure observation were performed to analyze the effects of the addition of minor elements Ti, B and Zr during solidification. The prominence of effect on grain refinement was in increasing order for Ti, Zr and B element. Fine grain size and an increase of the crystallization temperature for ${\alpha}$-Al solution were evident as the amount of addition elements increased in this study. Addition of 0.15wt% Ti was most effective for grain refinement, and the resulting grain size of ${\alpha}$-Al solution for shell mold and steel mold were $72.3{\mu}m$ and $23.5{\mu}m$, respectively. Fluidity and shrinkage tests were perform to evaluate the castability of the alloy. Maximum fluidity length and minimum ratio of micro shrinkage were recorded for 0.15wt% Ti addition due to the effect of the finest grain size.

• Korean Journal of Materials Research
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• v.27 no.10
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• pp.557-562
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• 2017

The microstructural evolution and modulation of mechanical properties were investigated for a $Ti_{65}Fe_{35}$ hypereutectic alloy by addition of $Bi_{53}In_{47}$ eutectic alloys. The microstructure of these alloys changed with the additional BiIn elements from a typical dendrite-eutectic composite to a bimodal eutectic structure with primary dendrite phases. In particular, the primary dendrite phase changed from a TiFe intermetallic compound into a ${\beta}$-Ti solid solution despite their higher Fe content. Compressive tests at room temperature demonstrated that the yield strength slightly decreased but the plasticity evidently increased with an increasing Bi-In content, which led to the formation of a bimodal eutectic structure (${\beta}$-Ti/TiFe + ${\beta}$-Ti/BiIn containing phase). Furthermore, the (Ti65Fe35)95(Bi53In47)5 alloy exhibited optimized mechanical properties with high strength (1319MPa) and reasonable plasticity (14.2 %). The results of this study indicate that the transition of the eutectic structure, the type of primary phases and the supersaturation in the ${\beta}$-Ti phase are crucial factors for controlling the mechanical properties of the ultrafine dendrite-eutectic composites.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.15-15
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• 1996