“…In addition, the aspect ratio representing the horizontal and vertical ratio of grains decreased from 3.15 in CP-Ti to 3.02 in Ti–Y. This result indicates that yttrium oxide (which arose from the addition of yttrium) inhibited grain growth by increasing the number of nucleation sites of α-Ti [34–38]. Figure 6 Average grain size in CP-Ti and Ti–Y alloy powder with the particle size range.…”
Ti-based alloy powder is an excellent candidate as an additive manufacturing material, owing to its high strength-to-weight ratio, corrosion resistance and biocompatibility. However, molten Ti is highly reactive with ceramic crucibles. Thus, only crucible-free techniques can be used, limiting the manufacturing. In this study, Ti-Y, CP-Titanium powder was manufactured using the vacuum induction gas atomization cold crucible (VIGA-CC) process, without using any master alloy; moreover, its properties were elucidated. Characterisations were performed to comparatively analyse the surface morphology, impurity content and mechanical properties of the synthesised powder. It was found that the powder had a uniform composition and was refined by the yttrium addition. The VIGA-CC process, by which alloy powders with various compositions can be prepared, is expected to expand the list of target alloys that can be used in additive manufacturing processes.
“…In addition, the aspect ratio representing the horizontal and vertical ratio of grains decreased from 3.15 in CP-Ti to 3.02 in Ti–Y. This result indicates that yttrium oxide (which arose from the addition of yttrium) inhibited grain growth by increasing the number of nucleation sites of α-Ti [34–38]. Figure 6 Average grain size in CP-Ti and Ti–Y alloy powder with the particle size range.…”
Ti-based alloy powder is an excellent candidate as an additive manufacturing material, owing to its high strength-to-weight ratio, corrosion resistance and biocompatibility. However, molten Ti is highly reactive with ceramic crucibles. Thus, only crucible-free techniques can be used, limiting the manufacturing. In this study, Ti-Y, CP-Titanium powder was manufactured using the vacuum induction gas atomization cold crucible (VIGA-CC) process, without using any master alloy; moreover, its properties were elucidated. Characterisations were performed to comparatively analyse the surface morphology, impurity content and mechanical properties of the synthesised powder. It was found that the powder had a uniform composition and was refined by the yttrium addition. The VIGA-CC process, by which alloy powders with various compositions can be prepared, is expected to expand the list of target alloys that can be used in additive manufacturing processes.
“…According to the literature, the addition of Y to the parent alloy and heat treatment can significantly improve the mechanical properties [6]. The addition of Y improves the thermal stability and corrosion resistance [7]. The addition of Y into an alloy can reduce the processing difficulty, improve the recrystallization of the material at high temperatures, and greatly increase the resistance to high temperature oxidation [8,9].…”
In this paper, a Co60Fe20Y20 film was sputtered onto Si (100) substrates with thicknesses ranging from 10 to 50 nm under four conditions to investigate the structure, magnetic properties, and surface energy. Under four conditions, the crystal structure of the CoFeY films was found to be amorphous by an X-ray diffraction analyzer (XRD), suggesting that yttrium (Y) added into CoFe films and can be refined in grain size and insufficient annealing temperatures do not induce enough thermal driving force to support grain growth. The saturation magnetization (MS) and low-frequency alternate-current magnetic susceptibility (χac) increased with the increase of the thicknesses and annealing temperatures, indicating the thickness effect and Y can be refined grain size and improved ferromagnetic spin exchange coupling. The highest Ms and χac values of the Co60Fe20Y20 films were 883 emu/cm3 and 0.26 when the annealed temperature was 300 °C and the thickness was 50 nm. The optimal resonance frequency (fres) was 50 Hz with the maximum χac value, indicating it could be used at a low frequency range. Moreover, the surface energy increased with the increase of the thickness and annealing temperature. The maximum surface energy of the annealed 300 °C film was 30.02 mJ/mm2 at 50 nm. Based on the magnetic and surface energy results, the optimal thickness was 50 nm annealed at 300 °C, which has the highest Ms, χac, and a strong adhesion, which can be as a free or pinned layer that could be combined with the magnetic tunneling layer and applied in magnetic fields.
“…In addition, a trace amount of P (<50 ppm) induced Ti-P phase at the grain boundary, which played the role of a grain growth inhibitor [ 11 ]. Similarly, grain boundary segregation was revealed to be an effective grain refinement method, where local enrichment of solute atoms at grain boundary occurs to reduce free energy, and finally, inhibit grain growth during heat treatments such as recrystallization [ 12 ]. Therefore, secondary phase formation at grain boundary such as β Ti phase would stabilize grain boundary, and grain refinement could be achieved by controlling Fe content.…”
Microstructures and corrosion properties of pure titanium were characterized when iron was used as a grain refiner. The added Fe element acted as a strong grain refiner for pure titanium by forming β Ti phase at grain boundaries, and 0.15 wt% Fe was revealed to be a sufficient amount to make the grain size of pure titanium below 20 μm, which was the requirement for the desired titanium cathode. However, corrosion resistance was decreased with the Fe amount added. From the open circuit potential (OCP) results, it was obvious that the TiO2 stability against the reducing acid environment was deteriorated with the Fe amount, which seemed to be the main reason for the decreased corrosion resistance. Electrochemical impedance spectroscopy (EIS) results showed that both the decrease in the compact oxide film’s resistance (Rb) and the appearance of the outer porous film occurred as a result of the dissolution of the TiO2 layer, whose phenomena became more apparent as more Fe was added.
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