• Title, Summary, Keyword: TiAl

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Phase Characterization and Oxidation Behavior of Ti-Al-N and Ti-Al-Si-N Coatings (Ti-Al-N과 Ti-Al-Si-N 코팅막의 상 특성 및 내산화 거동)

  • Kim, Jung-Wook;Jeon, Jun-Ha;Cho, Gun;Kim, Kwang-Ho
    • Journal of the Korean institute of surface engineering
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    • v.37 no.3
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    • pp.152-157
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    • 2004
  • Ti-Al-N ($Ti_{75}$ $Al_{25}$ N) and Ti-Al-Si-N ($Ti_{69}$ $Al_{23}$ $Si_{8}$N) coatings synthesized by a DC magnetron sputtering technique were studied comparatively with respect to phase characterization and high-temperature oxidation behavior. $Ti_{69}$ $Al_{23}$ $Si_{ 8}$N coating had a nanocomposite microstructure consisting of nanosized(Ti,Al,Si)N crystallites and amorphous $Si_3$$N_4$, with smooth surface morphology. Ti-Al-N coating of which surface $Al_2$$O_3$ layer formed during oxidation suppressed further oxidation. It was sufficiently stable against oxidation up to about $700^{\circ}C$. Ti-Al-Si-N coating showed better oxidation resistance because both surface Ab03 and near-surface $SiO_2$ layers suppressed further oxidation. XRD, GDOES, XPS, and scratch tests were performed.

The Study on Peak Disappearance of Minor Phase and Formation of ${Al_3}Ti$ in Mechanically Alloyed Al-Ti Samples (기계적 합금화한 Al-Ti 시료에서 미소상 피이크의 소멸현상과 ${Al_3}Ti$ 형성에 관한 연구)

  • Kim, Jin-Gon;Kim, Hye-Seong;Kim, Byeong-Hui
    • Korean Journal of Materials Research
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    • v.11 no.12
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    • pp.1035-1041
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    • 2001
  • The refining process and solubility of Ti in Al matrix during mechanical alloying (MA) were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM) as functions of alloy composition, milling time and ball to powder ratio (BPR). Mechanical alloyed samples were annealed for investigating their stability and the formation behavior of$Al_3Ti$in the temperature range from$200{\circ}C$to$600{\circ}C$. It is observed from present experimental that disappearance of Ti peaks in mechanically alloyed Al-10wt%Ti is not simply attributable to the dissolution of Ti into Al, but associated mainly with extreme refining and/or heavy straining of Ti particles The annealing of the mechanically alloyed Al-Ti powders show differences in aluminide formation behavior when Ti content in Al is equal to or less than l0wt% and higher than l5wt%Ti. When Ti-content in Al is equal to or less than l0wt%, the MA powders transform directly to a global equilibrium state forming $DO_{22}- type\;Al_3$Ti above$400{\circ}C$. In the Al-Ti samples with equal to or higher than l5wt%Ti, transitional phases of cubic$Al_3Ti$and tetragonal $Al_{24}Ti_8$ are formed above$400{\circ}C$. They are stable only below$500{\circ}C$, and, $DO_{22}-type\;Al_3Ti$ becomes dominant aluminide at temperature higher than$ 600{\circ}C$.

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Effect of Pre-Heat Treatment on Bonding Properties in Ti/Al/STS Clad Materials (Ti/Al/STS 클래드재의 접합특성에 미치는 예비 열처리의 영향)

  • Bae, Dong-Hyun;Jung, Su-Jung;Cho, Young-Rae;Jung, Won-Sup;Jung, Ho-Shin;Kang, Chang-Yong;Bae, Dong-Su
    • Korean Journal of Metals and Materials
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    • v.47 no.9
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    • pp.573-579
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    • 2009
  • Titanium/aluminum/stainless steel(Ti/Al/STS) clad materials have received much attention due to their high specific strength and corrosion-resisting properties. However, it is difficult to fabricate these materials, because titanium oxide is easily formed on the titanium surface during heat treatment. The aim of the present study is to derive optimized cladding conditions and thereupon obtain the stable quality of Ti/Al/STS clad materials. Ti sheets were prepared with and without pre-heat treatment and Ti/Al/STS clad materials were then fabricated by cold rolling and a post-heat treatment process. Microstructure of the Ti/Al and STS/Al interfaces was observed using a Scanning Electron Microscope(SEM) and an Energy Dispersed X-ray Analyser(EDX) in order to investigate the effects of Ti pre-heat treatment on the bond properties of Ti/Al/STS clad materials. Diffusion bonding was observed at both the Ti/Al and STS/Al interfaces. The bonding force of the clad material with non-heat treated Ti was higher than that with pre-heat treated Ti before the cladding process. The bonding force decreased rapidly beyond $400^{\circ}C$, because the formed Ti oxide inhibited the joining process between Ti and Al. Bonding forces of STS/Al were lower than those of Ti/Al, because brittle $Fe_3Al$, $Al_3Fe$ intermetallic compounds were formed at the interface of STS/Al during the cladding process. In addition, delamination of the clad material with pre-heat treated Ti was observed at the Ti/Al interface after a cupping test.

Formation of Al3Ti From Mechanically Alloyed Hyper-Peritectic Al-Ti Powder (기계적 합금화법으로 제조된 과포정 Al-Ti 합금에서 Al3Ti 형성에 관한 연구)

  • Kim, Hye-Sung;Suhr, Dong-Soo;Kim, Gyeung-Ho;Kum, Dong-Wha
    • Journal of the Korean Society for Heat Treatment
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    • v.9 no.1
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    • pp.1-11
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    • 1996
  • Mechanical alloying is an effective process to finely distribute inert dispersoids in an Al-TM(TM is a transition metal) system. It has been considered that high melting point aluminides are formed by precipitation from supersaturated Al(Ti) powder. This analysis is based on the fact that much higher content of TM than the solubioity can be dissolved in alpha aluminum during the high energy ball milling. Thus, decomposition behavior of Ti in the Al(Ti) was considered very important. But it is confirmed that the higher portion of Ti than Al(Ti) solid solution is existed as nano-sized Ti particles in the MA powders by high energy ball nilling from the XRD spectrum and TEM analysis in this study. Therefore, the role of undissolved TM particles affect the formation of aluminides should be suitably considered. In this study, we present experimental observation on the formation of $Al_3Ti$ fron mechanical alloyed Al-Ti alloys in the hyperperitectic region. This study showed that, in the mechanically alloyed Al-20wt%Ti specimen, intermediate phase of cubic $Al_3Ti$ and tetragonal $Al_{24}Ti_8$ formed at $300{\sim}400^{\circ}C$ and $400{\sim}500^{\circ}C$, respectively, before the MA state reaches to equilibrium at higher temperatures. The formation behavior of $Ll_2-Al_3Ti$ is interpreted by interdiffusion of Al and Ti in solid state based on the fact that large amount of nano-sized Ti particles exist in the milled powder. Present analysis indicated undissolved Ti particles of nanosize should have played an important role initiation the formation of $Al_3Ti$ phase during annealing.

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The Effects of Ti-B Addition on the Unidirectional Solidification of Al (Ti-B 첨가(添加)에 의한 Al 의 응고조직(凝固組織)에 관(關)한 연구(硏究))

  • Song, Yeon-Soo;Lee, Kye-Wan
    • Journal of Korea Foundry Society
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    • v.7 no.4
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    • pp.358-365
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    • 1987
  • To investigate the grain refining mechanism of Al by the addition of Ti-B, the unidirectional solidifications of 99.9%Al and 99.7%Al were performed under the condition of varing the pouring temperature. The solidification modes of Al were studied by the cooling curve analyses, metallographic and microprobe examinations. The results were as follows: 1) Grains were most refined with an addition of 0.15wt.%Ti-0.021wt.%B but the grain size with 0.2wt.%Ti-0.028wt.%B was increased. 2) The grain size of 99.7wt.%Al was even more refined than that of 99.9wt.%Al with the same amount of Ti-B. 3) As the pouring temperature increased, the grain size of pure Al and an alloy with 0.lwt.%Ti-0.014wt.%B was increased. However, an alloy with 0.2wt.%Ti-0.028wt.%B did not show any effects of temperature. 4) TiC(Al-Ti) and (Al-Ti-C) were identified as nucleants for Al.

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Structural Analyses and Properties of $Ti_{1-x}Al_xN$ Films Deposited by PACVD Using a $TiCl_4/AlCl_3/N_2/Ar/H_2$ Gas Mixture ($TiCl_4/AlCl_3/N_2/Ar/H_2$ 반응계를 사용하는 플라즈마화학증착법에 의한 $Ti_{1-x}Al_xN$ 박막의 구조분석 및 물성)

  • 김광호;이성호
    • Journal of the Korean Ceramic Society
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    • v.32 no.7
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    • pp.809-816
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    • 1995
  • Ti1-xAlxN films were successfully deposited on high speed steel and silicon wafer by plasma-assisted chemical vapor deposition using a TiCl4/AlCl3/N2/Ar/H2 gas mixture. Plasma process enabled N2 gas to nitride AlCl3, which is not possible in sense of thermodynamics. XPS analyses revealed that the deposited layer contained Al-N bond as well as Ti-N bond. Ti1-xAlxN films were polycrystalline and had single phase, B1-NaCl structure of TiN. Interplanar distance, d200, of (200) crystal plane of Ti1-xAlxN was, however, decreased with Al content, x. Al incorporation into TiN caused the grain size to be finer and changed strong (200) preferred orientation of TiN to random oriented microstructure. Those microstructural changes with Al addition resulted in the increase of micro-hardness of Ti1-xAlxN film up to 2800Kg/$\textrm{mm}^2$ compared with 1400Kg/$\textrm{mm}^2$ of TiN.

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Synthesis of (Ti,Al)N Powder by Interdiffusion Nitriding Method (상호확산법에 의한 (Ti,Al)N계 복합질화물의 합성)

  • Lee, Young-Ki;Kim, Jung-Yeul;Kim, Dong-Kun;Sohn, Yong-Un
    • Journal of the Korean Society for Heat Treatment
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    • v.10 no.2
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    • pp.138-149
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    • 1997
  • TiN and AlN are ceramic materials with extensive applications due to its excellent mechanical and chemical properties at elevated temperature. The purpose of this research is to develop the method for the synthesis of ternary nitride powder, titanium-aluminum-nitrogen system, which have an excellent property of both TiN and AlN. The ternary nitride such as $Ti_3AlN$, $Ti_2AlN$ and $Ti_3Al_2N_2$ can be synthesized by the interdiffusion nitriding method in Ar gas, however, the ternary nitride coexist with TiN, AlN, $Ti_3Al$ and ${\alpha}$-Ti. The ternary nitride are stable below $1400^{\circ}C$, but these are gradually decomposed into TiN, $Ti_3Al$ and AlN above $1400^{\circ}C$. The thermal oxidation characteristics of the Ti-Al-N compound synthesized by the interdiffusion nitriding method is superior to that of the TiN+AlN mixed powder, and the oxidation for both materials show the differential behaviors.

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Research on Microstructure and Properties of TiN, (Ti, Al)N and TiN/(Ti, Al)N Multilayer Coatings

  • Wang, She Quan;Chen, Li;Yin, Fei;Jia, Li
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.658-659
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    • 2006
  • Magnetron sputtered TiN, (Ti, Al)N and TiN/(Ti, Al)N multilayer coatings grown on cemented carbide substrates have been characterized by using electron probe microanalysis (EPMA), X-ray diffraction (XRD), scanning electron spectroscopy (SEM), nanoindentation, scratcher and cutting tests. Results show that TiN coating is bell mouth columnar structures, (Ti, Al)N coating is straight columnar structures and the modulation structure has been formed in the TiN/(Ti, Al)N multilayer coating. TiN/(Ti, Al)N multilayer coating exhibited higher hardness, better adhesion with substrate and excellent cutting performance compared with TiN and (Ti, Al)N coating.

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Synthesis and Properties of $Al_2$$O_3$-$TiO_2$Composites by Wet Method -1. Synthesis of $Al_2$$O_3$-$TiO_2$Composite Powders- (습식법에 의한 $Al_2$$O_3$-$TiO_2$복합체의 합성 및 특성연구 -1. $Al_2$$O_3$-$TiO_2$계 복합분체의 합성(1)-)

  • 류수착;엄지영
    • Journal of the Korean Ceramic Society
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    • v.38 no.5
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    • pp.412-417
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    • 2001
  • 본 연구는 습식법으로 수산화 알루미늄과 티타니아를 출발물질로 하여 $Al_2$O$_3$-TiO$_2$복합분체를 제조하였으며, 2 mol의 Al(OH)$_3$분말에 대하여 TiO$_2$분말량을 1, 3, 5, 7, 9, 11 wt%로 첨가하여 $Al_2$O$_3$-TiO$_2$복합분체의 특성을 조사하였다. 제조된 $Al_2$O$_3$-TiO$_2$계 복합분체는 $700^{\circ}C$~140$0^{\circ}C$까지 하소하여 XRD 분석을 한 결과 100$0^{\circ}C$까지는 TiO$_2$(rutile)상과 η-Al$_2$O$_3$상이 공존하다가 110$0^{\circ}C$부터 130$0^{\circ}C$까지는 η-Al$_2$O$_3$에서 $\alpha$-Al$_2$O$_3$로의 상전이가 일어나서 $\alpha$-Al$_2$O$_3$상과 TiO$_2$(rutile)상이 나타났으며 하소온도 140$0^{\circ}C$, TiO$_2$첨가량이 5 wt%일 때부터 $Al_2$TiO$_{5}$가 생성되기 시작하였다. TiO$_2$첨가량에 따른 비표면적값은 첨가량이 7 wt%까지는 감소하였으나 그 이상 첨가시 증가하였다. 입도분석 결과 평균입경은 15.74~23.21$mu extrm{m}$로서 TiO$_2$첨가량이 3 wt%일 때 가장 작은 값을 가졌으며 TiO$_2$첨가량은 5 wt% 이상부터 점차 감소하였다.

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CaO Crucible Induction Melting and Investment Casting of TiAl Alloys (TiAl 합금의 CaO 도가니 유도용융 및 정밀주조)

  • Kim, Myoung-Gyun;Sung, Si-Young;Kim, Young-Jig
    • Journal of Korea Foundry Society
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    • v.22 no.2
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    • pp.75-81
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    • 2002
  • The main objectives were to investigate the suitability of CaO crucible for melting TiAl alloys and to develop investment mold for investment casting of TiAl alloys. TiAl alloy specimen were prepared by plasma arc furnace under argon atmosphere. After melting of TiAl alloy using CaO crucible, the results showed that there is little contamination of oxygen in the TiAl bulk. Conventional vacuum induction furnaces can be readily adaptable to produce cast parts of TiAl without high skilled techniques. The determination of optical metallography and microhardness profiles in investment cast TiAl alloy rods has allowed the gradation of the relative thermal stability of the oxides examined. The molds used for the present study were $ZrO_2$, $Al_2O_3$, CaO stabilized $ZrO_2$ and $ZrSiO_4$. Even although high temperature of mold preheating, $Al_2O_3$ mold is a promising mold material for investment casting of TiAl alloys in terms of thermal stability, cost and handling strength. It is important to take thermal stability and preheating temperature of mold into consideration for investment casting of TiAl alloys.