• 한국주조공학회지
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• 제17권5호
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• pp.450-457
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• 1997

Effects of Ti addition and homogenizing heat treatment on the mechanical properties in Cu-Zn-Al alloy (high strength yellow brass) were investigated. Grain refinement was successfully achieved by Ti addition. The microstructure, which was composed of island or fine feather-like branched Ti compounds was changed to feather-like eutectic microstructure as the content of Ti increased. The highest hardness value was obtained for 0.5 wt.% Ti specimen and the second was Ti non-added specimen in as-cast condition. The highest tensile strength was obtained for 0.5 wt.% Ti specimen. Because of the presence of cast defects and worse castability, tensile strength decreased as the content of Ti increased. Elongation increased with increasing homogenizing time and temperature; remarkable increase was obtained for $400^{\circ}C$ homogenizing temperature in the 0.5 wt.% Ti specimen. For $500^{\circ}C$ and $600^{\circ}C$ homhgenizing, temperature, high elongation was obtained in 2 and 4 wt.% Ti specimen.

• 동력기계공학회지
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• 제17권4호
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• pp.103-108
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• 2013

This study was investigated the effect of austenitizing treatment the microstructure and mechanical properties in modified 440A steel, and the results were as follows. The amount of remaining carbide decreases with increasing the austenitizing treatment temperature, and all carbide is completely dissolved at $1250^{\circ}C$. The amount of remaining carbide decreases with increasing the austenitizing treatment time, but the carbide remains insoluble up to 120 minutes at $1050^{\circ}C$. The strength and hardness gradually decrease with increasing the austenitizing treatment temperature and is significantly lower at $1250^{\circ}C$, while the elongation and the impact value rapidly increase. The strength and hardness rapidly decrease, the elongation and impact value rapidly insrease with increasing the austenitizing treatment time and exhibit no change at above 120 minutes. The austenitizing treatment modified 440A steel is required for temperature of above $1050^{\circ}C$ and time of above 60 minutes.

• 대한금속재료학회지
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• 제50권6호
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• pp.413-418
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• 2012

This study was carried out to investigate the effect of reverse transformation on the mechanical properties in high manganese austenitic stainless steel. Over 95% of the austenite was transformed to deformation-induced martensite by 70% cold rolling. Reverse transformation became rapid above an annealing temperature of $550^{\circ}C$, but there was no significant transformation above $700^{\circ}C$. In addition, with an increasing annealing time at $700^{\circ}C$, reverse transformation was induced rapidly, but the transformation was almost completed at 10 min. There was a rapid decrese in strength and hardness with annealing at temperature above $550^{\circ}C$, while elongation increased rapidly above $600^{\circ}C$. At $700^{\circ}C$, hardness and strength decreased rapidly, and elongation increased steeply with an increasing reverse treatment time up to 10 min, whereas there were no significant change with a treatment time after 10 min. The reverse-transformed austenite showed an ultra-fine grain size less than $0.2{\mu}m$, which made it possible to strengthen the high manganese austenitic stainless steel.

• 한국염색가공학회지
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• 제31권3호
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• pp.187-194
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• 2019

Blowing film was prepared using polyester elastomer with thermally expandable microcapsule to investigate the optimum blowing properties and the film making process. Physical properties including specific gravity, blowing efficiency, foaming shape, tensile strength and elongation of polyester film were tested by varying the process condition of temperature and revolution per minutes of the extruder. The lowest specific gravity of 0.709 can be achieved with excellent foaming cells at $210^{\circ}C$ and 50 RPM conditions. The highest tensile strength and elongation was shown at $210^{\circ}C$, 100 RPM and $230^{\circ}C$, 25 RPM conditions. However, most of the prepared polyester films showed over $1kg_f/mm^2$ of tensile strength which is reasonable value to use in film applications.

• 한국잠사곤충학회지
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• 제14권1호
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• pp.43-47
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• 1972

견층부위별견사의 기계적특성을 파악하고저 Deniroscope와on을 이용하여 실험한바 다음과 같은 결과를 얻었다. 1) 견층별견사의 건조 및 습윤절단강도는 견사섬도감소율에 비례하여 저하한다. 2) 내층견사의 습윤항장력은 외층견사에 대하여 37%로 나타났다. 3) 습윤처리에 의한 전견층의 절단강도(g/d) 31%, 감소하였다. 4) 대섬도당 견사의 건조 및 습윤절단강도는 내층견사가 제일 높았다. 5) Apparent young's modulus는 내층견사에서 증가하였다. 6) 습윤견사의 절단신도는 건조견사에 비해 15% 증가하였다.

• Bulletin of the Korean Chemical Society
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• 제4권4호
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• pp.162-169
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• 1983

The swelling and stress-elongation experiments have been performed for two kinds of gels of tactic poly (2-hydroxyethyl methacrylate) (P-HEMA) with varying crosslinker concentrations. The gels of isotactic and syndiotactic P-HEMA were swollen in aqueous salt solutions upon varying molal concentrations. The solute used were NaCl, $MgCl_2$, $Na_2SO_4$, $MgSO_4$ and urea. The water content at equilibrium swelling and the salt partition coefficient were determined, and stress-elongation curves of the gels were obtained. From these results, the effective number of chain (${\nu}_e$) and the Flory-Huggins interaction parameter (${\chi}_1$) were also obtained. The swelling experiment was also performed under varying solvents, and the degree of swelling was determined. The solubility parameter of P-HEMA was obtained as 13.4 (cal/mole)$^{l/2}$ using the correlation between the degree of swelling and the solubility parameter (${\delta}_1$) of solvents. The mechanical properties of syndiotactic P-HEMA is stronger than that of isotactic P-HEMA, and the water content of both gels become smaller when the crosslinking increases. Isotactic P-HEMA contains more water content than syndiotactic P-HEMA does.

• 대한금속재료학회지
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• 제49권3호
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• pp.197-202
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• 2011

This study was carried out to investigate the precipitation behavior of ${\chi}$ phase and effect of ${\chi}-phase$ which precipitated at the initial stage of aging on mechanical properties of 25%Cr-7%Ni-4%Mo-0.2%N super duplex stainless steel. ${\chi}-phase$ was precipitated mainly at the interface of ferrite / austenite phases and inside of the ferrite phase at the initial stage of aging, and it was transformed into ${\sigma}-phase$ with an increase of aging time. The ferrite phase was decomposed into new $austenite({\gamma}_2)phase$ and ${\sigma}-phase$ by aging treatment. The hardness and tensile strength of the initial stage of aging when ${\chi}-phase$ was precipitated did not changed considerably, while elongation rapidly decreased. Accordingly, it is considered that ${\chi}-phase$ didn't affect the hardness and strength significantly, but it affected the elongation.

• 한국분말재료학회지
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• 제29권4호
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• pp.325-331
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• 2022

Beta-titanium alloys are used in many industries due to their increased elongation resulting from their BCC structure and low modulus of elasticity. However, there are many limitations to their use due to the high cost of beta-stabilizer elements. In this study, biocompatible Ti-Mo-Fe beta titanium alloys are designed by replacing costly beta-stabilizer elements (e.g., Nb, Zr, or Ta) with inexpensive Mo and Fe elements. Additionally, Ti-Mo-Fe alloys designed with different Fe contents are fabricated using powder metallurgy. Fe is a strong, biocompatible beta-stabilizer element and a low-cost alloying element. The mechanical properties of the Ti-Mo-Fe metastable beta titanium alloys are analyzed in relation to the microstructural changes. When the Fe content increases, the tensile strength and elongation decrease due to brittle fracture despite a decreasing pore fraction. It is confirmed that the hardness and tensile strength of Ti-5Mo-2Fe P/M improve to more than 360 Hv and 900 MPa, respectively.

• 한국압력기기공학회 논문집
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• 제19권1호
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• pp.11-19
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• 2023

Additive manufacturing technology, called as 3D printing, is one of fourth industrial revolution technologies that can drive innovation in the manufacturing process, and thus should be applied to nuclear industry for various purposes according to the manufacturing trend change in the future. In this paper, we performed tensile tests of 3D printed stainless steel 316L as-built specimens manufactured by two types of technology; DED (Directed Energy Deposition) and PBF (Powder Bed Fusion). Their mechanical properties (tensile strength, yield strength, elongation and reduction of area) were compared. As a result of comparison, the mechanical properties of the PBF specimens were slightly better than those of DED specimens. In the same additive type of specimens, the tensile and yield strength of specimens in the X and Y direction were higher than those in the Z direction, but the elongation and ROA were lower.

• 한국주조공학회지
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• 제21권6호
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• pp.336-342
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• 2001

This study was carried out to examine the effects of adding 0.3at.%Hf in Fe-30at.%Al-5at.%Cr alloy on the variation of microstructures and hot workability. The effect of hot rolling on mechanical properties was estimated by measuring the elongation and tensile strength after rolling at 800 and 1000 respectively. Microstructure of Fe-30at.%Al-5at.%Cr alloy was consisted of large equiaxed grains and it was changed to quasi-equiaxed or columnar structures by adding 0.3at.%Hf to Fe-30at.%Al-5at.%Cr alloy. Every specimens showed a decreased tensile strength after hot rolling compared to that of before rolling. The elongation was increased by hot rolling. Remarkable changes in elongation by hot rollong was observed such as from 1.4% to 4.5% elongation at the specimen of 0.3at.%Hf added to Fe-30at.%Al-5at.%Cr. Fe-30at.%Al-5at.%Cr alloy showed typical cleavage fracture on tensile failure and hot rolling has negligible effects on fracture mode in this alloy. However at the alloy containing Hf fracture mode was changed by hot rolling from intergranular to mixed intergranular and transgranular fracture mode.