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The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation behavior.The as-built microstructure showed fine cell and columnar structure due to high cooling rate.Ti element segrega-tion was observed in inter-cell/inter-columnar area.After post heat-treatment,the initially-observed cell structure disappeared,instead bimodal Ni3(Al,Ti)particles formed.High temperature(1273 K and 1373 K)oxidation test results showed parabolic oxidation curves regardless of temperature and initial microstructure.The as-built IN738LC fabricated via the selective laser melting process displayed oxida-tion resistance similar to or slightly better than that of IN738LC fabricated via wrought or cast process.Heat-treated SLM IN738LC,although had similar oxidation weight-gain values to those of the SLM as-built material at 1273 K,showed relatively better oxidation resistance at 1373 K.Bimodal Ni3(Al,Ti)precipitate formed in the post heat treatment changed the local chemical composition,thereby led to changes in alumina former/chromia former location and fraction on the alloy surface.It was concluded that in heat-treated IN738LC increased alumina former fraction was found,and this resulted in excellent oxidation resistance and relatively low weight-gain. 相似文献
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Joon-Young Heo Jin-Han Gwon Jong-Kwan Park Kee-Ahn Lee 《Metals and Materials International》2018,24(3):586-596
Hypereutectic Al–Si alloy is an aluminum alloy containing at least 12.6 wt.% Si. It is necessary to evenly control the primary Si particle size and distribution in hypereutectic Al–Si alloy. In order to achieve this, there have been attempts to manufacture hypereutectic Al–Si alloy through a liquid phase sintering. This study investigated the microstructures and high temperature mechanical properties of hypereutectic Al–14Si–Cu–Mg alloy manufactured by liquid phase sintering process and changes in them after T6 heat treatment. Microstructural observation identified large amounts of small primary Si particles evenly distributed in the matrix, and small amounts of various precipitation phases were found in grain interiors and grain boundaries. After T6 heat treatment, the primary Si particle size and shape did not change significantly, but the size and distribution of CuAl2 (θ) and AlCuMgSi (Q) changed. Hardness tests measured 97.36 HV after sintering and 142.5 HV after heat treatment. Compression tests were performed from room temperature to 300 °C. The results represented that yield strength was greater after heat treatment (RT?~?300 °C: 351?~?93 MPa) than after sintering (RT?~?300 °C: 210?~?89 MPa). Fracture surface analysis identified cracks developing mostly along the interface between the primary Si particles and the matrix with some differences among temperature conditions. In addition, brittle fracture mode was found after T6 heat treatment. 相似文献
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Joon-Young Heo Min-Seok Baek Kwang-Jun Euh Kee-Ahn Lee 《Metals and Materials International》2018,24(5):992-1001
This study investigated the microstructure, tensile and fatigue properties of Al–5 wt.%Mg alloy manufactured by twin roll strip casting. Strips cast as a fabricated (F) specimen and a specimen heat treated (O) at 400 °C/5 h were produced and compared. In the F specimen, microstructural observation discovered clustered precipitates in the center area, while in the O specimen precipitates were relatively more evenly distributed. Al, Al6(Mn, Fe), Mg2Al3 and Mg2Si phases were observed. However, most of the Mg2Al3 phase in the heat-treated O specimen was dissolved. A room temperature tensile test measured yield strength of 177.7 MPa, ultimate tensile strength of 286.1 MPa and elongation of 11.1% in the F specimen and 167.7 MPa (YS), 301.5 MPa (UTS) and 24.6% (EL) in the O specimen. A high cycle fatigue test measured a fatigue limit of 145 MPa in the F specimen and 165 MPa in the O specimen, and the O specimen achieved greater fatigue properties in all fatigue stress conditions. The tensile and fatigue fracture surfaces of the above-mentioned specimens were observed, and this study attempted to investigate the tensile and fatigue deformation behavior of strip cast Al–5 wt.%Mg based on the findings. 相似文献
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Jae-Sung Oh Min-Chul Shim Man-Ho Park Kee-Ahn Lee 《Metals and Materials International》2014,20(5):915-921
This study investigated the high temperature oxidation behavior of newly developed Ni-Cr-Al powder porous metal. High temperature isothermal oxidation tests were conducted at 900, 1000 and 1100 °C temperatures for 24 h under an atmosphere of 79% N2 + 21% O2 gas. Oxidation weight gain vs. time curves represented typical oxidation behavior of parabolic shape. Weight gain increased with increasing oxidation temperature. Ni-Cr-Al porous metal mainly created oxides such as α-Al203, Cr2O3, NiCr2O4. The α-Al203 oxide could be still maintained up to 1100 °C oxidation temperature as a thick and stable protective layer. It was noted that Ni-Cr-Al porous metal had better high temperature oxidation resistance than those of other Ni-based and Fe-based porous metals. The catastrophic degradation of oxidation resistance especially at very high temperature was not observed up to 1100 °C in this porous metal. The micro-mechanism of high temperature oxidation of Ni-Cr-Al porous metal was also discussed. 相似文献
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Manufacturing and Macroscopic Properties of Cold Sprayed Cu-In Coating Material for Sputtering Target 总被引:1,自引:0,他引:1
Young-Min Jin Jin-Hyeon Cho Dong-Yong Park Ju-Ho Kim Kee-Ahn Lee 《Journal of Thermal Spray Technology》2011,20(3):497-507
This study attempted to manufacture a Cu-In coating layer via the cold spray process and to investigate the applicability
of the layer as a sputtering target material. In addition, changes made to the microstructure and properties of the layer
due to annealing heat treatment were evaluated, compared, and analyzed. To examine the microstructural and property changes
made to the Cu-In coating layer and Cu coating layer (comparison material), ICP, XRD, SEM, and other tests were conducted;
purity, density, hardness, porosity, and bond-strength were measured. The results showed that coating layers with thickness
of 20 mm (Cu) and 810 μm (Cu-In) could be manufactured via cold spraying under optimal process conditions. With the Cu-In
coating layer, the pure Cu and intermetallic compounds of Cu7In3 and CuIn4 were found to exist inside the layer regardless of annealing heat treatment. The preannealing inconsistent microstructure
of the layer, whose phases were difficult to distinguish was found to have transformed into one with clearer phase distinction
and fine, consistent grains following thermal treatment via a progress of recovery, recrystallization, and grain growth. The
porosity and hardness values of the coating layers were 1.4% and 133.9 HV, respectively, for Cu and 3.54% and 476.6 HV, respectively,
for Cu-In. The values of the Cu-In layer were higher than those of the Cu layer in terms of porosity and hardness, which declined
drastically after annealing. With the porosity of the Cu-In coating layer in particular, the higher value found during the
preannealing stage dropped to 0.36% after heat treatment of 773 K/1 h as the level on a par with pure Cu (0.44%), thus indicating
the improved quality of the Cu-In layer. Moreover, the results of the bond-strength measurement performed on the Cu-In coating
layer and annealing treated materials revealed the strength to be relatively high for heat treated coating layers. Based on
the findings of this study and on the comparison and discussion of the properties that are typically required of the target
material, the Cu-In coating layer manufactured via cold spray process and annealing heat treatment can be said to be applicable
as sputtering target in the future. 相似文献
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Kyu-Sik Kim Ji-Sang Yu Juyeon Won Changhee Lee See-Jo Kim Seong Lee Kee-Ahn Lee 《Metallurgical and Materials Transactions A》2013,44(11):4876-4879
The compressive deformation behavior in the thickness direction of a kinetic-sprayed pure-aluminum layer whose thickness is ~15 mm was investigated. The yield strength of coating material was 200 MPa, and a unique strain softening phenomenon occurred even at room temperature. Due to the initial severely deformed structure of the kinetic-sprayed coating material based on the results of microstructure analysis, the production of high-strength metal bulk materials using kinetic spray processes was deemed possible. 相似文献
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This study investigated the microstructure and the room and high temperature mechanical properties of Fe–Cr–B alloy manufactured by metal injection molding. In addition, hot isostatic pressing was performed to increase the density of the material, and a comparison of properties was made. Microstructural observation confirmed a bi-continuous structure composed of a three-dimensional network of α-Fe phase and (Cr,Fe)2B phase. The HIPed specimen featured a well-formed adhesion between the α-Fe phase and boride, and the number of fine pores was significantly reduced. The tensile results confirmed that the HIPed specimen (RT to 900 °C) had higher strengths compared to the as-sintered specimen, and the change of elongation starting from 700 °C was significantly greater in the HIPed specimen. Fractography suggested that cracks propagated mostly along the interface between the α-Fe matrix and boride in the as-sintered specimen, while direct fracture of boride was observed in addition to interface separation in the HIPed specimen. 相似文献
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Sung-Hwan Choi Song-Yi Kim Jung-Yeul Yun Young-Min Kong Byoung-Kee Kim Kee-Ahn Lee 《Metals and Materials International》2011,17(2):301-307
This study investigated the effect of the pore size of Ni-22.4%Fe-22%Cr-6%Al porous metal on its hightemperature oxidation.
Two types of open porous metals with pore sizes of 800 μm and 580 μm were used. A 24-hour isothermal oxidation test was conducted
at three different temperatures of 900 °C, 1000 °C, and 1100 °C under a 79% N2 + 21% O2 atmosphere. The results of the BET analysis revealed that the specific surface area increased as the pore size decreased
from 800 μm to 580 μm. The high-temperature oxidation results showed that porous metals exhibited far lower levels of oxidation
resistance compared with bulk metals, and that the oxidation resistance of porous metals decreased with a decreasing pore
size. According to the microstructural observations of the oxide layers, the 900 °C and 1000 °C oxidation layer contained
Ni, Cr, and Al oxides mainly on the strut. The 800 μm porous metal strut exhibited similar oxidation behavior at 1100 °C to
that found at lower temperatures. In contrast, the 580 μm porous metal strut was found to consist of Ni and Fe oxides in the
upper layer and Ni, Cr, and Al oxides in the lower layer, representing a low oxidation resistance. For powders affixed to
the strut inside the porous metal, a different oxide-forming behavior from that of the strut was observed. In addition, the
Ni-Fe-Cr-Al porous metal high-temperature oxidation microscopic mechanism is also discussed. 相似文献