• Korean Journal of Materials Research
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• v.11 no.5
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• pp.393-397
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• 2001

Fer the purpose of improving ductility of $Al_3$Ti intermetallic compound has potential to industrial application, we investigated formation behavior of cubic Ll$_2$ structure and effect of Mn addition. Nanocrystalline cubic Ll$_2$Al$_3$Ti intermetallic compound, has 10nm size of grain, was fabricated by mechanical alloying for 20hr at the composition of Al-8Mn-25Ti. Ternary cubic Ll$_2$Al$_3$Ti, added Mn, did not showed phase transformation from Ll$_2$ to D0$_{23}$ or D0$_{22}$ unlike binary cubic Ll$_2$Al$_3$Ti and maintained Ll$_2$ structure.

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.817-822
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• 2012

Nano powders of $Al_2O_3$ and $TiO_2$ compounds made by high energy ball milling were pulsed current activated sintered for studying their sintering behaviors and mechanical properties. The advantage of this process is that it allows very quick densification to near theoretical density and inhibition of grain growth. Nano-structured $Al_2TiO_5$ with small amount of $Al_2O_3$ and$TiO_2$ was formed by sintering at $1300^{\circ}C$ for 5 minute, in which average grain size was about 96 nm. Hardness and fracture toughness of the nano-structured $Al_2TiO_5$ compound with a small amount of $Al_2O_3$ and$TiO_2$ were $602kg/mm^2$ and $2.6MPa{\cdot}m^{1/2}$, respectively.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.478-481
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• 1996

Disproportionation reaction is very important and interesting reaction to be applied to such surface treatment as metal, alloy, compound coating, a surface etching and so on. In gaseous system, the reaction of Al chloride is applied to Al and Al alloy coating, and the similar reaction of Ti chloride is also used for Ti, Ti alloy and Ti compound coating. As for aqueous system, this reaction is utilized to such metal coat as Sn etc. and metal etching such as Cu, Fe and so on. Also in molten salts system, this reaction has many application for surface treatment like metal, alloy and compound coatings for corrosion, wear, heat resistance and so forth. For instance, carbide film, nitride film, boride film, alloy film, quite new different film from the components of substrate material are coated in single and multiple component film system by the disproportionation reaction.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.147-148
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• 2007

The compound, Ti3(Al,Si)C2, was synthesized by hot pressing a powder mixture of TiCX, Al and Si. Its oxidation at 900 and 1000 oC in air for up to 50 h resulted in the formation of rutile-TiO2, -Al2O3 and amorphous SiO2. During oxidation, Ti diffused outwards to form the outer TiO2 layer, and oxygen was transported inwards to form the inner mixed layer.

• Transactions of Materials Processing
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• v.31 no.4
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• pp.179-185
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• 2022

The influence of post-roll bonding heat treatment conditions such as temperature and time on the variation in the diffusion layer, generated at the bonding interface and the subsequent mechanical properties of the roll-bonded Ti grade 1/Al1050/Ti grade 1 sheets, was systematically investigated. The intermetallic compound (IMC) phase generated by post heat treatment conditions adopted in this study was obviously indexed as monolithic TiAl₃. Whereas the thickness of IMC layer generated by annealing at 500 ℃ was approximately 100 nm scale, it drastically increased above 1.5 ㎛ when annealed at 600 ℃. Uniaxial tensile and peel tests were then performed to compare mechanical properties. As a result, the bonding strength drastically increased above 7.9 N/mm by annealing at 600 ℃, which implies that proper annealing condition was a prerequisite, to improving interface bonding strength as well as global elongation properties for Ti/Al/Ti 3-ply sheet.

• Korean Journal of Materials Research
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• v.25 no.8
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• pp.398-402
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• 2015

Fundamental studies of microstructural changes and high temperature deformation of titanium aluminide (TiAl) were conducted from the view point of the effect of Al content in order to develop the manufacturing process of TiAl. Microstructures in an as cast state consisted mainly of lamellar structure irrespective of Al content. By homogenization at 1473 K, the microstructures of Ti-49Al and Ti-51Al were transformed into an equiaxial structure which was composed of ${\gamma}$-TiAl, while the lamellar structure that was observed in Ti-46Al and Ti-47Al was much more stable. We found that the reduction of Al content suppressed the formation of equiaxial grains and resulted in a microstructure of only a lamellar structure. On Ti-49Al and Ti-51Al, dynamic recrystallization occurred during high temperature deformation, and the microstructure was transformed into a fine equiaxial one, while the microstructures of Ti-46Al and Ti-47Al contained few recrystallized grains and consisted mainly of a deformed lamellar structure. We observed that on the low-Al alloys the lamellar structure under hard mode deformation conditions deformed as kink observed B2-NiAl. High temperature deformation characteristics of TiAl were strongly affected by Al content. An increase of Al content resulted in a decrease of peak stress and activation energy for plastic deformation and an increase of the recrystallization ratio in TiAl.

• Korean Journal of Materials Research
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• v.18 no.1
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• pp.51-56
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• 2008

The crystal structures and morphologies of precipitates in $L1_0$-ordered TiAl intermetallics containing nitrogen were investigated by transmission electron microscopy (TEM). Under aging at an approximate temperature of 1073 K after quenching from 1423 K, TiAl hardens appreciably due to the nitride precipitation. TEM observations revealed that needle-like precipitates, which lie only in one direction parallel to the [001] axis of the $L1_0$-TiAl matrix, appear in the matrix preferentially at the dislocations. Selected area electron diffraction (SAED) pattern analyses showed that the needle-shaped precipitate is perovskite-type $Ti_3AlN$ (P-phase). The orientation relationship between the P-phase and the $L1_0$-TiAl matrix was found to be $(001)_P//(001)_{TiAl}\;and\;[010]_P//[010]_{TiAl}$. By aging at higher temperatures or for longer periods at 1073 K, plate-like precipitates of $Ti_2AlN$ (H-phase) with a hexagonal structure formed on the {111} planes of the $L1_0$-TiAl matrix. The orientation relationship between the $Ti_2AlN$ and the $L1_0$-TiAl matrix is $(0001)_H//(111)_{TiAl}\;and\;_H//_{TiAl}$.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.7
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• pp.711-717
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• 2013

Titanium (Ti) metal and its alloys are desirable materials for ship hulls and other structures because of their high strength, light weight and corrosion-resistance. And light weight and corrosion-resistant aluminum (Al) is the ideal metal for shipbuilding. The joining of Ti and Al dissimilar metals is one of the effective measures to reduce weight of the structures or to save rare metals. Ti and Al have great differences in materials properties, and intermetallic compounds such as Ti3Al, TiAl, TiAl3 are easily formed at the contacting surface between Ti and Al. Thus, welding or joining of Ti and Al is considered to be extremely difficult. However, it was clarified that ultra-high speed welding could suppress the formation of intermetallic compounds in the previous study. Results of tensile shear strength increases with an increase in the welding speed, and therefore extremely high welding speed (50m/min in this study) is good to dissimilar weldability for Ti and Al. In this study, therefore, full penetration dissimilar lap welding of Ti (upper) - Al (lower) and Al (upper) - Ti (lower) with single-mode fiber laser was tried at ultra-high welding speed, and the microstructure of the interface zones in the dissimilar Al and Ti weld beads was investigated.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.133-139
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• 2014

Titanium (Ti) metal and its alloys are desirable materials for ship hulls and other ocean structures because of their high strength, corrosion-resistance and light weight properties. And light weight and corrosion-resistant aluminum (Al) is the ideal metal for shipbuilding. The joining of Ti and Al dissimilar metals is one of the effective methode to reduce weight of the structures. Ti and Al have great differences in materials properties, and intermetallic compounds such as $Ti_3Al$, TiAl, $TiAl_3$ are easily formed at the contacting surface between Ti and Al. Thus, dissimilar welding and joining of Ti and Al are considered to be very difficult. However, it was clarified that ultra-high speed welding could suppress the formation of intermetallic compounds in the previous study. Results of tensile shear strength increases with an increase in the welding speed, and therefore extremely high welding speed (50 m/min) is good to dissimilar weldability for Ti and Al. In this study, therefore, full penetration dissimilar lap welding of Ti (upper) - Al (lower) and Al (upper) - Ti (lower) with single-mode fiber laser was tried at ultra-high welding speed, and the microstructure of the interface zones in the dissimilar Al and Ti weld beads was investigated.

• Korean Journal of Materials Research
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• v.15 no.7
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• pp.439-443
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• 2005

The oxidation behavior and the thermal stability of nanocrystalline Al-25Ti-8Mn intermetallic compound were investigated. $Al_3Ti$ intermetallic compound, which has a potential for high temperature structural material, was fabricated by mechanical alloying(MA) with $8at.\%$ Mn to enhance the thermal stability and ductility. And Al-25Ti-8Mn intermetallic compound was sintered by spark plasma sintering(SPS) at $700^{\circ}C$. After sintering process, cubic $Ll_2$ structure was maintained without phase transformation and the grain size was about 50nm. To investigate the oxidation behavior of the specimens, thermal gravimetric analysis(TGA) was performed at 700, 800, 900, and $1000^{\circ}C$ for 24 h in $O_2$. As the temperature increased from $700^{\circ}C\;to\;900^{\circ}C$ the weight gain of specimens increased. However at $1000^{\circ}C$, unlike the oxidation behavior of $700^{\circ}C\;to\;900^{\circ}C$, the weight gain of specimen decreased drastically and the transition from linear rate region to parabolic rate region occurred rapidly due to the dense $\alpha-Al_2O_3$.