• 한국재료학회지
• /
• 제11권12호
• /
• pp.1057-1062
• /
• 2001

We investigated the change of mechanical properties for TiNi shape memory alloy by heat treatment. 6061Al matrix composites with TiNi shape memory alloy as reinforcement were fabricated by vacuum casting. TiNi alloy has the maximum tensile strength at 673K treated and there is no change of tensile strength and hardness at 448K treated. The composites, prepared by vacuum casting, showed good interface bonding by vacuum casting. It was about 3$\mu\textrm{m}$ of thickness of the diffusion layer. Tensile strength of the composite was in higher than that of 6061Al alloy as increased value of about 70MPa at room temperature and about 110MPa at 363K. We thought that the increase of the tensile strength at 363K was due to reverse transformation of the TiNi shape memory alloy.

• 대한치과기공학회지
• /
• 제27권1호
• /
• pp.65-71
• /
• 2005

Experimental Ti-13%Zr and Ti-13%Zr-5%Cu alloys were made in an argon-arc melting furnace. The grade 2 CP Ti was used to control. The alloys were cast into phosphate bonded $SiO_2$ investment molds using an argon-arc casting machine, and The hardness and microstructures of the castings were investigated in order to reveal their possible use for new dental casting materials and to collect useful data for alloy design. The hardness of the Ti-13%Zr-5%Cu alloy(379Hv) became higher than that of Ti-13%Zr(317Hv) alloy, and the hardness of this alloys became higher than that of CP Ti(247Hv). Increasing in the hardness of the Ti-13%Zr-5%Cu alloy was considered to be solid solution hardening as the Ti-Zr system shows a completely solid solution for both high temperature $\beta$phase and low temperature $\alpha$ phase and also the inclusion of the eutectoid structure($\alpha Ti+Ti_{2}Cu$). No martensitic structures are observed in the specimen made of CP Ti, but Ti-13%Zr and Ti-13%Zr-5%Cu alloys show a kind of martensitic structure. Ti-13%Zr-5%Cu shows the finest microstructure. From these results, it was concluded that new alloys for dental casting materials should be designed as Ti-Zr-Cu based alloys.

• 대한금속재료학회지
• /
• 제50권2호
• /
• pp.164-170
• /
• 2012

Nanotubular structure formation on the Ti-6Al-4V and Ti-Ta alloy surfaces by electrochemical methods has been studied using the anodizing method. A nanotube layer was formed on Ti alloys in 1.0 M $H_3PO_4$ electrolyte with small additions of $F^-$ ions. The nanotube nucleation and growth of the ${\alpha}$-phase and ${\beta}$-phase appeared differently, and showed different morphology for Cp-Ti, Ti-6Al-4V and Ti-Ta alloys. In the ${\alpha}$-phase of Cp-Ti and martensite ${\alpha}^{\prime}$ and in the ${\alpha}^{{\prime}{\prime}}$ and ${\beta}$-phase of the Ti-Ta alloy, the nanotube showed a clearly highly ordered $TiO_2$ layer. In the case of the Ti-Ta alloy, the pore size of the nanotube was smaller than that of the Cp-Ti due to the ${\beta}$-stabilizing Ta element. In the case of the Ti-6Al-4V alloy, the ${\alpha}$-phase showed a stable porous structure; the ${\beta}$-phase was dissolved entirely. The nanotube with two-size scale and high order showed itself on Ti-Ta alloys with increasing Ta content.

• 소성∙가공
• /
• 제19권4호
• /
• pp.230-235
• /
• 2010

Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only for aerospace parts but also for bio prothesis and motorcycle. However, the database is insufficient in the titanium alloy for press forming process. In this study, the effect of temperature on the forming limit diagram was investigated for Ti-6Al-4V titanium alloy sheet through the Hecker‘s punch stretching test at elevated temperature. Experimental results obtained in this study can provide a database for the development of press forming process at elevated temperature of Ti-6Al-4V titanium alloy sheet. From the experimental studies it can be concluded that the formability of Ti-6Al-4V titanium alloy sheet is governed by the ductile failure for the testing temperature. The formability of Ti-6Al-4V titanium alloy sheet at $700^{\circ}C$ increases about 7 times compared with that at room temperature.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
• /
• pp.846-847
• /
• 2006

The composite used in this paper was prepared by hot-pressing ball-milled Mg alloy powders, in which NiTi shape memory alloy fibers in a row were sandwiched. The microstructure and property were examined. It is shown that the composite consisted of a homogenous matrix with uniformly distributed NiTi shape memory alloy fibers, recrystallization took place in the Mg alloy matrix which was subjected to plastic deformation an adequate bonding formed between the matrix and fibers; the density and tensile strength of the composite increased after the hot-forging; the hot-forging process is capable of improving properties of the composite.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.12-13
• /
• 2006

The spherical and high quality Titanium fine powder "Tilop" has been produced with gas atomization furnace, Sumitomo Titanium Corporation originally designed. Recently, a new process which can produce Ti-alloy(Ti-6Al-4V) powders by utilizing our gas atomization process, of which raw material is sponge titanium pre-mixed with alloy chips or granules has been also developed. The particle size of gas atomized Ti-alloy powder and the mechanical properties of sintered Ti-alloy compacts prepared by metal injection molding were discussed in this study.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1995년도 하계학술대회 논문집 C
• /
• pp.1013-1015
• /
• 1995

The electrical properties of Al/TiN/Ti contact according to post anneal ins conditions are investigated at submicron contacts. $N^+$ contact resistance increases with increasing alloy temperature while $P^+$ contact resistance slightly decreases. The contact tentage current increases wi th increasing alloy temperature for both $N^+$ and $P^+$ contacts. The contact resistance and leakage current of $N^+$ contact increases with increasing alloy tide. $P^+$ contact resistance decreases with increasing alloy time but $P^+$ contact tentage current increases. The contact resistance and contact leakage current increases with increasing alloy cycles for both $N^+$ and $P^+$ contacts.

• 한국정밀공학회지
• /
• 제20권4호
• /
• pp.20-28
• /
• 2003

The machinability of Ti-6Al-4V titanium alloy and tool wear behavior in machining of Ti-6Al-4V titanium alloy was studied to understand the machining characteristics. This material is one of the strong candidate materials in present and future aerospace or medical applications. Recently, their usage has already been broaden to everyday's commercial applications such as golf club heads, finger rings and many decorative items. To anticipate the general use of this material and development of the titanium alloys in domestic facilities, the review and the study of the machining parameters for those alloys are necessary. This study is concentrated to the machining parameters of the Ti-6Al-4V alloy due to their dominant position in the production of titanium alloys.

• Corrosion Science and Technology
• /
• 제16권6호
• /
• pp.317-327
• /
• 2017

The change in the oxidation behavior of three types of B-added ultrahigh strength martensitic steels containing Ti and Nb induced by applying constant cathodic current was investigated. In a 3% NaCl+0.3% $NH_4SCN$ solution, the overall polarization behavior of the three alloys was similar, and degradation of the oxide film was observed in the three alloys after applying constant cathodic current. A significant increase in the anodic current density was observed in the Nb-added alloy, while it was diminished in the Ti-added alloy. Both Ti and Nb alloying decreased the hydrogen overpotential by forming NbC and TiC particles. In addition, the thickest oxide film was formed on the Ti-added alloy, but the addition of Nb decreased the film thickness. Therefore, it was concluded that the remarkable increase in the anodic current density of Nb-added alloy induced by applying constant cathodic current density was attributed to the formation of the thinnest oxide film less protective to hydrogen absorption, and the addition of Ti effectively blocked the hydrogen absorption by forming TiC particles and a relatively thick oxide film.

• 대한금속재료학회지
• /
• 제49권2호
• /
• pp.121-127
• /
• 2011

The mechanical properties of the various heat treatment conditions on Ti-15Mo-3Nb-3Al-0.2Si alloy plates were examined. XRD patterns from the surface of Ti-15Mo-3Nb-3Al-0.2Si were analyzed as a solution-treated Ti alloy has the single-phase ${\beta}$ structure whereas the aged Ti alloys have the ${\beta}$ matrix embedded with ${\alpha}$ needles. High strength (~1500 MPa) with decent ductility (7%) was obtained by the Ti alloy double aged at $300^{\circ}C$ and $520^{\circ}C$ for 8 hours each. The double-aged alloy exhibits the finer structure than the single-aged alloy at $300^{\circ}C$ for 8 hours because of the higher nucleation rate of ${\alpha}$ needles at an initial low aging temperature ($320^{\circ}C$). TEM observation revealed that the fine nanostructure with ${\alpha}$ needles in the ${\beta}$ matrix ensured the excellent mechanical properties in the double aged Ti-15Mo-3Nb-3Al-0.2Si alloy. In the solution treated alloy, the yield drop, stress-serrations and the ductility minimum typically associated with dynamic strain aging can be attributed to the dynamic interaction between dislocations and oxygen atoms. The yield drop and the stress serration were not observed in aged samples because the geometrically introduced dislocations due to phase precipitates suppressed the dynamic strain aging.