• Transactions of Materials Processing
• /
• v.31 no.2
• /
• pp.73-80
• /
• 2022

In this study, a developed Mg-5Bi-2Al-0.4Mn (BAM520, wt%) alloy was successfully extruded at an extremely high speed of 70 m/min. Microstructural evolution during extrusion and the microstructural characteristics and tensile properties of the very-high-speed extruded BAM520 alloy were then investigated. The homogenized BAM520 billet contained only thermally stable Mg₃Bi₂ phase particles without any Mg₁₇Al₁₂ phase with a low melting temperature. Therefore, the BAM520 alloy exhibited excellent extrudability. The very-high-speed extruded BAM520 alloy had a completely recrystallized grain structure and a typical basal fiber texture. Despite the extremely high extrusion speed of 70 m/min, the extruded BAM520 alloy had a high ultimate tensile strength of 280 MPa due to combined strengthening effects of a small grain size, numerous fine Mg₃Bi₂ particles, and strong basal texture.

• Progress in Superconductivity
• /
• v.4 no.1
• /
• pp.94-98
• /
• 2002

Two kinds of multifilament Bi-2223／Ag tapes, which are different in the precursor calcination temperatures, were heat treated for different time (12, 20, 30, 50, 70, or 100 h) firstly to obtain varied B2223 contents, and then followed by the same pressing and sintering cycles. The relation of the 2223 phase contents after the first sintering and the transport property of the fully processed tapes was studied. The results show that 75-80% 2223 phase formed in tapes before the first cold pressing is beneficial to get a high $I_{c}$ in the final tapes. Compensating the total heat treatment time of the tapes first sintered for 20 h to the same length as that first sintered for 50 h in the subsequent sintering stages, different $I_{c}$ enhancements were observed in these two tapes. No improvement on $I_{c}$ was found in the tape made from the powder calcined at higher temperature, whereas for the tape prepared with the lower temperature calcined powder, the $I_{c}$ was increased to the same level as that first sintered for 50 h. The 2223 contents before the intermediate mechanical work is related to the residual reactants, especially to the liquid phase, which is of vital importance to the phase conversion and healing microcracks, meanwhile, to the size and distribution of the non-superconducting secondary phases. The lower temperature calcined powder resulted in slow formation of 2223 phase, but also provided more reactants and liquid phase for the further phase conversion, as a consequence, for the Improvement of $I_{c}$. c/.

• Korean Journal of Materials Research
• /
• v.4 no.1
• /
• pp.97-106
• /
• 1994

The dependence of the electrical resistivity on the eutectic composition and growth rates was investigated in the unidirectionally solidified Sb-InSb and Sn-Bi eutectic alloy systems, which were generally classified into the groups of f-f and nf-f eutectic system. Sb-InSb alloys containing 26-34wt.% In and Sn-Bi alloys containing 53-65wt.%Bi were prepared in vacuum sealed in a silica tube, and then these were unidirectionally solidified. Electrical resistivity of the specimens prepared by cutting the crystal section in parallel with the transverse direction and by cutting in longitudinal direction was measured. As the growth rate increased, the Sb-InSb and Sn-Bi eutectic alloys showed that the resistivity of longitudinal to the growth direction was increased but that of transverse to the growth direction was decreased. In the case of Sb-InSb eutectic alloy, increas~ng the phase boundary area and decreasing the fiber directionallity caused to increase the $p \; \parallel$ , while increasing the phase boundary area increased the $p \; \\perp$ As expected, the eutectic microstructure could be analysed well in terms of electrical resistivity.

• Journal of information and communication convergence engineering
• /
• v.4 no.4
• /
• pp.158-161
• /
• 2006

[ $Bi_2Sr_2Ca_nCu_{n+1}O_y(n{\geq}0)$ ] thin film is fabricatedvia two different processes using an ion beam sputtering method i.e. co-deposition and layer-by-layer deposition. A single phase of Bi2212 can be fabricated via the co-deposition process. While it cannot be obtained by the layer-by-layer process. Ultra-low growth rate in our ion beam sputtering system brings out the difference in Bi element adsorption between the two processes and results in only 30% adsorption against total incident Bi amount by layer-by-layer deposition, in contrast to enough Bi adsorption by co-deposition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.151-152
• /
• 2006

Bi-Te thermoelectric powder was fabricated by mechanical alloying method for 1 to 10 hours under vacuum in planetary mill. We investigated the properties of mechanically alloyed Bi-Te powder by thermal analysis, X-ray diffractometer and FESEM with EDS Bi-Te raw material was formed to $Bi_2Te_3$ phase at condition over 3.5 hours of mechanical alloying time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.10a
• /
• pp.40-44
• /
• 2000

$Bi_2Sr_2Ca_nCu_{n+1}O_y$($n{\geq}0$; BSCCO)thin film is fabricated via two different processes using an ion beam sputtering method i.e. co-deposition and layer-by-layer deposition. A single phase of Bi2212 can be fabricated via the co-deposition process. While it cannot be obtained by the layer-by-layer process. Ultra-low growth rate in our ion beam sputtering system brings out the difference in Bi element adsorption between the two processes and results in only 30% adsorption against total incident Bi amount by layer-by-layer deposition, in contrast to enough Bi adsorption by co-deposition.

• Journal of Korea Foundry Society
• /
• v.10 no.5
• /
• pp.392-398
• /
• 1990

To improve free-cutting property, fine Pb, Bi particles is necessary to be distributed evenly in Al-Cu alloy. The control of added element size and distribution are very difficult because of the physical properties of Pb, Bi. The effect of master alloy compositions on microstructure and particle distribution was investigated. The ribbon shape of Pb-50wt% Bi master alloy showed the best results. And Ti addition improved even distribution of Pb, Bi particles. Particles grown from $L_2$ phase were considered to be the Pb, Bi compound.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.9
• /
• pp.796-800
• /
• 2000

Bi$_2$Sr$_2$Ca$_{n}$Cu$_{n+1}$ O$_{y}$(n$\geq$0; BSCCO) thin film is fabricated via two different processes using an ion beam sputtering method i.e. co-deposition and layer-by-layer deposition. A single phase of Bi2212 can be fabricated via the co-deposition process. While it cannot be obtained by the layer-by-layer process. Ultra-low growth rate in our ion beam sputtering system brings out the difference in Bi element adsorption between the two processes and results in only 30% adsorption against total incident Bi amount by layer-by-layer deposition, in contrast to enough Bi adsorption by co-deposition.on.n.

• Proceedings of the KWS Conference
• /
• 2007.11a
• /
• pp.282-284
• /
• 2007

The superconductor characteristics of BSCCO spray films by Heat treatment was studied. $Bi_2Sr_2CaCu_2O_x$(Bi-2212) is high-Tc superconductor(HTS) coatings have been prepared by Heat treatment. Where high current carrying capabilities are required and therefore thick film and bulk material are called for, the Bi2Sr2Ca1Cu2O8-d(Bi-2212)compound has evoleved as one of the most promising. and the Bi-2212 HTS coating layer is synthesized through the peritectic reaction between Sr-Ca-Cu oxide coating layer and Bi-Cu oxide coating layer by partial melting process. The superconducting characteristics depends on the spray distance which was related to the spray particle melt. The Bi-2212 HTS layer consists of the whisker growth and secondary phase in 2212 layer were observed.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.2
• /
• pp.352-354
• /
• 2010

The effects of Au addition on the structure and the superconducting properties of Bi system bulk have been investigated. Au exists in the metalic form in above materials. It does not affect the formation and structure of the BiSrCaCuO(2223) phase. The superconducting transition temperature Tc does not change for $Bi_{1.7}Pb_{0.3}Sr_2Ca_2Cu_3O$ composite However Au doping can make the grains smaller. Metallic Au can make gathers on the grains boundary and lead to the increment of critical transport current density. The current density of $Bi_{1.7}Pb_{0.3}Sr_2Ca_2Cu_3Au_{0.5}O$ was 1000A/$cm^2$ at liquid nitrogen temperature.