• Journal of Korea Foundry Society
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• v.17 no.3
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• pp.237-244
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• 1997

This study has been carried out to investigate into the influence of solidification conditions mold on the structure and mechanical properties of Al-5wt%Mg alloy by metallic mold casting. The percentage of equiaxed grain of Al-5wt%Mg alloy castings increased both when pouring temperature decreased and when the low part or bottom of metallic mold was cooled. The hardness was checked and showed that hardness of outside in the castings was higher than that inside, and that it is the highest at the pouring temperature of $680^{\circ}C$. The castings had the highest U.T.S. and elongation when the bottom of metallic mold was cooled. At the same pouring temperature, the structure of castings was changed as the position of cooling parts of metallic mold was varied. When the castings were solidified through cooling of the bottom of the metallic mold, the morphology of Fe intermetallic compound has tendency to change to a Chinese script and the U.T.S. and elongation of Al-5wt.%Mg alloy castings was increased.

• Korean Journal of Metals and Materials
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• v.49 no.3
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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.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.61-65
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• 2020

Rheo-diecasting with stirring has been used in many material industries. As the 4th Industrial Revolution approaches the world, eco-friendly high-strength and light-weight materials become more important. Casting methods have been studied and used for aluminum-alloy automobile parts. This study carried out the effect analysis of the micro-structure and mechanical properties, such as yield/ultimate tensile strength, elongation, and hardness, of A356 using the 6-pole EMS (electro-magnetic stirring) casting process with a high electromagnetic force. As a result, the hardness and elongation of the A356 after T6 heat-treatment show a significant improvement, respectively, by 20% and 50%.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.49-54
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• 2013

Recently welding of aluminum material is actively carried out to make lightweight in the fields of LNG vessels, aircraft, chemical plants, etc. To obtain high strength, hardness and elongation, elements such as manganese, zinc, silicon, etc should be added in aluminum alloy, which has been improved on the mechanical properties like precipitation hardening, age hardening, loosening, corrosion resistance acid resistance. Ar gas is used as a shielding gas of MIG welding for aluminum, also $N_2$, $O_2$, $CO_2$, $H_2$ etc can be added depending on the composition of the alloy. In this study, Ar + $O_2$, Ar, and He were used for welding, hardness, penetration status and changes in composition of penetrated parts were compared and analyzed. This made it possible to know the status and changes of the process in the penetrated parts depending on used gas throughout this study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.1
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• pp.42-46
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• 2003

Liquid PVC, which is used widely as fiber coating, has brilliant non-luster effect, but it decreases flexibility of coated fiber surface. We used liquid silicone rubber in elastomer series as a coating material to alleviate this problem. We have conducted the former liquid PVC processing and used pressure of roller and preliminary hardening of processing. In this experiment, We measured 70 degree of hardness, 10.3 MPa of tensile strength and 200fs of tensile elongation of Liquid PVC-coated plastic fiber. We measured 40 degree of hardness, 5.1 MPa of tensile strength and 460% of tensile elongation of Liquid silicone PVC-coated plastic fiber. Therefore, Without the second process, Liquid silicone rubber coating increased non-luster effect and flexibility of plastic fiber surface more than Liquid PVC coating.

• Korean Journal of Metals and Materials
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• v.50 no.6
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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.

• Journal of Power System Engineering
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• v.16 no.3
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• pp.51-56
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• 2012

The effect of deformation induced martensite transformation on the mechanical properties in austenitic stainless steel with high Mn was studied. ${\alpha}$'-martensite was formed by deformation in austenitic stainless steel with high Mn. Deformation induced ${\alpha}$'-martensite was formed with surface relief by cold rolling. With the increase of deformation degree, volume fraction of deformation induced martensite was increased rapidly in early stage of deformation and then, increased slowly. With the increase of deformation degree, hardness and tensile strength were rapidly increased with linear relations, while elongation was rapidly decreased and then slowly decreased. Hardness, tensile strengths and elongation were influenced strongly by deformation induced martensite.

• Journal of Korea Foundry Society
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• v.15 no.6
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• pp.558-565
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• 1995

Effects of high Si-P addition on microstructure and mechanical properties of thin ductile cast iron have been investigated. The amount of silicon addition have fixed on 4.0wt% and the amounts of phosphorus addition and thickness of specimen have been varied from 0.05 to 0.8wt% and ${\phi}13mm$, ${\phi}10mm$ and ${\phi}6mm$, respectively. As the casting thickness decreased, the average diameter of spheroidal graphite was decreased and the hardness of the cast iron increased. By adding P, the average diameter of spheroidal graphite was increased and the count of the spheroidal graphite was decreased continuously. And the tensile strength and the elongation was decreased, and the hardness was increased. With the P added more than 0.2wt%, the abraded amount was decreased significantly. The addition of P improved the wear resistance and the hardness of thin ductile cast iron.

• Journal of Welding and Joining
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• v.13 no.3
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• pp.125-133
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• 1995

Rene80 superalloy was liquid phase diffusion bonded by using pure boron (B) as an insert material. As a basic study for the possibility of practical application of this bonding method, hardness and high temperature tensile strength of the bonded joint and metallurgical analysis were investigated. As experimental results, hardness of the bonded joint was homogenized after bonding and the tensile strength at 1144K was obtained to 90% of that of base metal. But there were some problems to be improved also, that means the joint was hardened after bonding due to increase of B content and elongation was much lower than that of base metal. Flat area and (Mo, Cr, W) boride, which should be harmful for bonding strength, were observed on the fractured surface of the tensile tested specimen.

• Journal of Power System Engineering
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• v.11 no.4
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• pp.86-91
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• 2007

This study was investigated to know the effect of subzero treatment in austempered ductile cast iron. Retained austenite transformed to martensite by subzero treatment. With decreasing subzero treatment temperature, more volume fraction of retained austenite transformed to martensite and transformed to martensite above 30% by subzero treatment temperature at $-196^{\circ}C$. With decreasing subzero treatment temperature, the value of strength and hardness increased but the value of elongation and impact value decreased. In case of subzero treatment at $-196^{\circ}C$, hardness value increased about 18% and impact value decreased by above 20%. We could find that subzero treated specimens had a little of effect on the tensile properties but had very much effect on the hardness and value of the impact.