• 한국분말재료학회지
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• 제10권6호
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• pp.383-389
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• 2003

As in other areas of materials technology, the tendency towards light weight constructions becomes more and more important also for powder metallurgy. The development is mainly driven by the automotive industry looking for mass reduction of vehicles as a major factor for fuel economy. Powder metallurgy has to offer a number of interesting areas including the development of sintered materials of light metals. PM aluminium alloys with improved properties are on the way to replace ferrous pars. For high temperature applications in the engine, titanium aluminide based materials offer a great potential, e.g. for exhaust valves. The PM route using elemental powders and reactions sintering is considered to be a cost effective way for net shape parts production. Furthermore it is expected that lower costs for titanium raw materials coming from metallurgical activities will offer new chances for sintered parts with titanium alloys. The field of cellular metals expands with the hollow sphere technique, that can provide materials of many metals and alloys with a great flexibility in structure modifications. These structures are expected to be used in improving the safety (crash absoption) and noise reduction in cars in the near future and offer great potential for many other applications.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.726-731
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• 2002

Reaction synthesis is a process to form ceramics, intermetallics and their composites from elemental powder mixture. Application of this process to a surface modification techniques has a possibilities to enable the process at a lower temperature or for a shorter time, although synthesized materials are likely to include voids and unreacted elements. This paper intend to examine the effect of Si addition to the mixture of Al and Ni on the densification of synthesized Ni-Al intermetallic compounds and to evaluate the surface properties of obtained coatings. By the Si addition, exothermic reaction temperature to form Ni-Al intermetallic was lowered to be below the melting point of Al. Si soluted $Al_3$Ni$_2$, $Al_3$Ni and $Al_{6}$Ni$_3$Si were mainly formed in the coating layer when powder mixture was heated to 973K for 300s. Besides, densification was enhanced by increasing hot press pressure, Si additions and heating rate. When the composition of eutectic Al-Si reaches 78%, void ratio of sintered compact reduced to 0.4%. It is caused by higher flowability of Al-Si liquid phase generated and its infiltration into the void. Since the hardness of NiAl(Si) compound (about 600HV) formed in the coating layer is higher than that of Ni-Al compound (about 400HV), coating layer with high density and superior wear property is obtained by hot press using reaction synthesis from Al-Ni-Si powder mixture.

• 한국재료학회지
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• 제11권1호
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• pp.34-38
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• 2001

Fe-28%Al($Fe_3Al$)과 Fe-28%Al-4%Cr($Fe_3Al-4Cr$) 금속간화합물을 대기중 1073, 1273, 1473k의 온도에서 최고 17일까지 장시간 산화시켰다. $Fe_3Al-4Cr$의 산화저항은 근본적으로 $Fe_3Al$과 거의 비슷하거나, 약간 우수하였다. $Fe_3Al$ 위에 형성된 산화물은 거의 순수한 ${\alpha}-AL_2O_3$로만 구성되어 있었으며, $Fe_3Al-4Cr$ 위에 형성된 산화물은 약간의 Fe와 Cr 이온이 고용된 ${\alpha}-AL_2O_3$로 구성되어 있었다. 외부산화막을 형성하기 위해 모재원소의 외부확산에 의해 산화물-모재 계면에는 Kirkendall 기공이 존재하였다. $Fe_3Al(-4Cr)$ 표면에 형성된 산화막은 1273k가지는 비교적 얇고 치밀하였으나, 1473k에서 산화막의 박리와 함께 상대적으로 큰 무게증가가 발생하였다.

• Advances in materials Research
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• 제1권1호
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• pp.51-74
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• 2012

A powder metallurgy-based rapid consolidation technique, Plasma Pressure Compaction ($P^2C^{(R)}$), was utilized to produce near-net shape parts of gamma titanium aluminides (${\gamma}$-TiAl). Micron-sized ${\gamma}$-TiAl powders, composed of Ti-50%Al and Ti-48%Al-2%Cr-2%Nb (at%), were rapidly consolidated to form near-net shape ${\gamma}$-TiAl parts in the form of 1.0" (25.4 mm) diameter discs, as well as $3"{\times}2.25"$ ($76.2mm{\times}57.2mm$) tiles, having a thickness of 0.25" (6.35 mm). The ${\gamma}$-TiAl parts were consolidated to near theoretical density. The microstructural morphology of the consolidated parts was found to vary with consolidation conditions. Mechanical properties exhibited a strong dependence on microstructural morphology and grain size. Because of the rapid consolidation process used here, grain growth during consolidation was minimal, which in turn led to enhanced mechanical properties. Consolidated ${\gamma}$-TiAl samples corresponding to Ti-48%Al-2%Cr-2%Nb composition with a duplex microstructure (with an average grain size of $5{\mu}m$) exhibited superior mechanical properties. Flexural strength, ductility, elastic modulus and fracture toughness for these samples were as high as 1238 MPa, 2.3%, 154.58 GPa and 17.95 MPa $m^{1/2}$, respectively. The high temperature mechanical properties of the consolidated ${\gamma}$-TiAl samples were characterized in air and vacuum and were found to retain flexural strength and elastic modulus for temperatures up to $700^{\circ}C$. At high temperatures, the flexural strength of ${\gamma}$-TiAl samples with Ti-50%Al composition deteriorated in air by 10% as compared to that in vacuum. ${\gamma}$-TiAl samples with Ti-48%Al-2%Nb-2%Cr composition exhibited better if not equal flexural strength in air than in vacuum at high temperatures.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.95-95
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• 2009

Zinc coatings provide the most effective and economical way of protecting steel against corrosion. There are three types of galvanizing lines typically used in production line in galvanizing industries,Galvanize (GI) coating (Zn-0.1-0.3%Al), Galfan coating (Zn-5%Al), Galvalume(GL) coating (45%Zn-Al). In continuous Galvanizing lines, the immersed bath hardware (e.g. bearings, sink, stabilizer, and corrector rolls, and also support roll arms and snout tip) are subjected to corrosion and wear failure. Understanding the reaction of these materials with the molten Zn alloy is becomes scientific and commercial interest. To investigate the reaction with molten Zn alloys, static immersion test performed for 4, 8, 16, and 24 Hr. Two different baths used for the static immersion, which are molten Zn and molten Zn-55%Al. Microstructures characterization of each of the materials and intermetallic layer formed in the reaction zone was performed using optical microscope, SEM and EDS. The thickness of the reaction layer is examined using image analysis to determine the kinetics of the reaction. The phase dominated by two distinct phase which are eutectic carbide and matrix. The morphology of the intermetallic phase formed by molten Zn is discrete phase showing high dissolution of the material, and the intermetallic phase formed by Zn-55wt%Al is continuous. Aluminum reacts readily with the materials compare to Zinc, forming iron aluminide intermetallic layer ($Fe_2Al_5$) at the interface and leaving zinc behind.

• 한국재료학회지
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• 제31권8호
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• pp.439-444
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• 2021

The oxidation resistance of the diffusion aluminide bond coat (BC) is compromised largely by interdiffusion (ID) effects on coated turbine blades of aeroengines. The present study is designed to understand the influence of ID on βNiAl coatings or BC. In this regard, nickel substrate and CMSX-4 superalloy are deposited. In total, four sets of BCs are developed, i.e. pure βNiAl (on Ni substrate), simple βNiAl (on CMSX-4 substrate), Zr-βNiAl (on CMSX-4 substrate) and Pt-βNiAl (on CMSX-4 substrate). The main aim of this study is to understand the interdiffusion of Al, Zr and Pt during preparation and oxidation. In addition, the beneficial effects of both Zr and platinum are assessed. Pure βNiAl and simple βNiAl show Ni-out-diffusion, whereas for platinum inward diffusion to the substrate is noticed under vacuum treatment. Interestingly, Zr-βNiAl shows the least ID in all BCs and exhibit stability under both vacuum and oxidation treatments. However, its spallation resistance is slightly lower than that of Pt-βNiAl BC. All BCs show similar oxide growth trends, except for Zr-βNiAl, which exhibits two-stage oxidations, i.e. transient and steady-state. Moreover, it is suggested that the localized spallation in all BCs is caused by βNiAl - γ'-Ni₃Al transformation.

• 한국재료학회지
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• 제10권8호
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• pp.569-574
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• 2000

고온구조용 재료로의 사용이 기대되는 $Al_3Hf$ 및 $Al_3Ta$ 금속간화합물의 연성을 향상시키기 위하여 SPEX mill을 이용한 기계적합금화시 $Ll_2$ 상의 생성거동과 이에 미치는 제 3 원소의 영향을 조사하였다. Al-25%Hf 혼합분말의 경우에는 기계적합금화 6시간부터 $Ll_2$$Al_3Hf$ 금속간화합물의 생성되었으나, Al-25%Ta의 경우에는 30시간까지도 $D0_{22}$ $Al_3Ta$ 금속간화합물만 생성되었고, $Ll_2$상은 생성되지 않았다. Al-12.5%M-25%MTa(M = Cu, Zn, Mn, Fe, Ni) 조성으로 제 3 원소를 첨가하여 20시간 동안 기계적합금화한 결과 Cu과 Zn의 경우에는 $D0_{22}$ 구조 금속간화합물만 생성되었고, Mn, Fe, Ni을 첨가한 경우에는 $600^{\circ}C$에서 등온열처리 후 D0(sub)22상으로 상변태되는 비정질상이 생성된 것으로 보아 이러한 제 3 원소의 첨가는 Cu와 Zn를 첨가한 경우에는 2원계와 마찬가지로 $Ll_2$상과 $D0_{22}$ 상간의 에너지 차이를 극복하기 못한 것으로 생각된다 한편, Al-12.5%M-25%Hf조성으로 Cu과 Zn를 첨가한 경우게는 2원계와 마찬가지로 $Ll_2$구조의 금속간화합물이 생성되었으나, Mn, Fe, Ni을 첨가한 경우에는 Al-12.5%M-25%MTa(M = Cu, Zn, Mn, Fe, Ni) 계와 같이 비정질이 생성된 것으로 보아 Ni, Nn, Fe는 $AL_3X$ 금속간화합물을 비정질화시키는 경향이 강한 것으로 생각된다.로 생각된다.