• Korean Journal of Metals and Materials
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• v.50 no.10
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• pp.711-720
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• 2012

In this study, the effect of aging treatment on the microstructure and tensile properties of AZ61-xPd (x = 0, 1 and 2 wt%) alloys were investigated. The microstructure of as-cast AZ61-xPd alloys mainly consisted of ${\alpha}-Mg$, $Mg_{17}Al_{12}$ and $Al_4Pd$ phases. After solution treatment, most of the $Mg_{17}Al_{12}$ phases were dissolved into the Mg matrix. Thereafter, $Mg_{17}Al_{12}$ phases were finely formed and distributed near thermally stable $Al_4Pd$ phases and inside the grains through aging treatment at $220^{\circ}C$ during 88 hours. With the aging at $220^{\circ}C$, the peak aged AZ61-xPd alloys showed higher hardness than as-cast and solution treated AZ61-xPd alloys. In particular, the AZ61-1Pd alloy was optimized due to refined $Mg_{17}Al_{12}$ and $Al_4Pd$ phases. Further, the peak aging time was reduced with increasing Pd addition (>1 wt%). Tensile strength was increased by Pd addition at $25^{\circ}C$, $150^{\circ}C$, both as-cast and peak aged AZ61-xPd alloys. After aging treatment, room and high temperature tensile strength were increased more than the as-cast specimens. The AZ61-1Pd alloy especially showed the largest strength increase range. Elongation was decreased with addition Pd at $25^{\circ}C$ and $150^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.4
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• pp.303-312
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• 1999

An investigation of the CrMoV rotor steel weldment which experienced by cyclic thermal aging heat treatment and as-received condition was performed. This evaluation was carried out to confirm whether this type of weldment is appropriate for the service environment in terms of microstructural examinations, microhardness measurements and tensile tests. The cyclic thermal aging heat treatment, containing continuous heating and cooling thermal cycle was programmed to simulate the real rotor service condition. The heat treatment was performed for 40 cycles(5920hrs). The results indicated that the weldment was composed of 4 different regions such as heat affected zone of the base metal, butter weld(initial weld), full thickness weld(final weld) and the base metal. The double welding process was applied to eliminate the susceptibility of reheat cracking at heat affected zone of base metal. The grain refinement at the HAZ due to the welding process could reduce the possibility of cracking susceptibility, but its tensile properties was appeared to be low due to the weld metal in as-received condition. The benefit effect, grain refinement was extended with carbides coarsening during the cyclic thermal aging heat treatment. However the poor mechanical properties of the weldment was more degraded as undergoing the heat treatment.

• Journal of Conservation Science
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• v.35 no.5
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• pp.416-429
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• 2019

Bongchae is primarily employed for toning, which is the last step in the conservation treatment of paper's cultural properties. The objective of this study is to identify the coloring patterns of four types of Bongchae(Bonram, Gamboge, Yeonji, and Daeja) and determine the associated color change patterns through accelerated aging experiments. By examining the coloring patterns, it is observed that Yeonji, Bonram, and Daeja are painted as particles, whereas Gamboge indicates a close state of coating. Results obtained from X-ray diffraction analysis of Bongchae indicate that the presence of quartz, calcite, and pyrophyllite can be equally detected in Bonram, Yeonji, and Daeja. Additionally, the presence of goethite is also detected in Daeja. Gamboge becomes discolored from yellow to orange color during wet thermal aging, and Gamboge and Yeonji become decolorized during UV irradiation aging. Hence, cultural properties of paper colored with Gamboge can be predicted to become discolored to orange color by alkalis and can be darkened by UV rays because the decolorization of Gamboge and Yeonji occurs preferentially.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.392-397
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• 2019

A cold roll-bonding process is applied to fabricate an AA6061/AA5052/AA6061 three-layer clad sheet. Two AA6061 and one AA5052 sheets of 2 mm thickness, 40 mm width, and 300 mm length are stacked, with the AA5052 sheet located in the center. After surface treatment such as degreasing and wire brushing, sample is reduced to a thickness of 1.5 mm by multi-pass cold rolling. The rolling is performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 400 mm at rolling speed of 6.0 m/sec. The roll bonded AA6061/AA5052/AA6061 complex sheet is then hardened by natural aging(T4) and artificial aging(T6) treatments. The microstructures of the as-roll bonded and age-hardened Al complex sheets are revealed by optical microscopy; the mechanical properties are investigated by tensile testing and hardness testing. After rolling, the roll-bonded AA6061/AA5052/AA6061 sheets show a typical deformation structure in which grains are elongated in the rolling direction. However, after T4 and T6 aging treatment, there is a recrystallization structure consisting of coarse equiaxed grains in both AA5052 and AA6061 sheets. The as roll-bonded specimen shows a sandwich structure in which an AA5052 sheet is inserted into two AA6061 sheets with higher hardness. However, after T4 and T6 aging treatment, there is a different sandwich structure in which the hardness of the upper and lower layers of the AA6061 sheets is higher than that of the center of the AA5052 sheet. The strength values of the T4 and T6 age-treated specimens are found to increase by 1.3 and 1.4 times, respectively, compared to that value of the starting material.

• Korean Journal of Materials Research
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• v.32 no.3
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• pp.161-167
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• 2022

A cold roll-bonding process is applied to fabricate an AA6061/AA5052/AA6061/AA5052 layered sheet. Two AA6061 and one AA5052 sheets of 2mm thickness, 40mm width and 300mm length are alternately stacked, then reduced to a thickness of 2.0 mm by multi-pass cold rolling after surface treatment such as degreasing and wire brushing. The rolling is performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 400 mm at a rolling speed of 6.0 m/sec. The roll-bonded AA6061/AA5052/AA6061/AA5052 layered sheet is then hardened by natural aging (T4) and artificial aging (T6) treatments. The microstructure of the as-roll bonded and the age-hardened Al sheets was revealed by SEM observation; the mechanical properties were investigated by tensile testing and hardness testing. After T4 and T6 aging treatment, the specimens had a recrystallization structure consisting of coarse equiaxed grains in both AA5052 and AA6061 regions. The as-roll-bonded specimen showed a clad structure in which the hardness of AA5052 regions was higher than that of AA6061 regions. However, after T4 and T6 aging treatment, specimens exhibited different structures, with hardness of AA6061 regions higher than that of AA5052 regions. Strengths of T6 and T4 age-treated specimens were found to increase by 1.55 and 1.36 times, respectively, compared to the value of the starting material.

• Korean Journal of Materials Research
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• v.33 no.12
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• pp.565-571
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• 2023

AA1050/AA6061/AA1050 layered sheet was fabricated by cold roll-bonding process and subsequently T4 and T6 aging-treated. Two commercial AA1050 sheets of 1 mm thickness and one AA6061 sheet of 2 mm thickness were stacked up so that an AA6061 sheet was located between two AA1050 sheets. After surface treatments such as degreasing and wire brushing, they were then roll-bonded to a thickness of 2 mm by cold rolling. The roll-bonded Al sheets were then processed by natural aging (T4) and artificial aging (T6) treatments. The as roll-bonded Al sheets showed a typical deformation structure, where the grains are elongated in the rolling direction. However, after the T4 and T6 aging treatments, the Al sheets had a recrystallized structure consisting of coarse grains in both the AA5052 and AA6061 regions with different grain sizes in each. In addition, the sheets showed an inhomogeneous hardness distribution in the thickness direction, with higher hardness in AA6061 than in AA1050 after the T4 and T6 age treatments. The tensile strength of the T6-treated specimen was higher than that of the T4-treated one. However, the strength-ductility balance was much better in the T4-treated specimen than the T6-treated one. The tensile properties of the Al sheets fabricated in the present study were compared with those in a previous study.

• Food Science of Animal Resources
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• v.39 no.1
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• pp.54-64
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• 2019

Wet and dry aging methods were applied to improve the quality of three different beef cuts (butt, rump, and sirloin) from Hanwoo cows (quality grade 2, approximately 50-mon-old). After 28 d of wet aging (vacuum packaged; temperature, $2{\pm}1^{\circ}C$) and dry aging (air velocity, 2-7 m/s; temperature, $1{\pm}1^{\circ}C$; humidity, $85{\pm}10%$), proximate composition, cooking loss, water holding capacity, shear force, color, nucleotides content, and sensory properties were compared with a non-aged control (2 d postmortem). Both wet and dry aging significantly increased the water holding capacity of the butt cuts. Dry aging in all beef cuts induced lower cooking loss than that in wet-aged cuts. Shear force of all beef cuts was decreased after both wet and dry aging and CIE $L^*$, $a^*$, and $b^*$ color values in butt and sirloin cuts were higher in both wet and dry aging (p<0.05) groups than those in the non-aged control. Regardless of the aging method used, inosine-5'-monophosphate content among beef cuts was the same. The sensory panel scored significantly higher values in tenderness, flavor, and overall acceptability for dry-aged beef regardless of the beef cuts tested compared to non- and wet-aged cuts. In addition, dry-aged beef resulted in similar overall acceptability among the different beef cuts, whereas that in wet-aged meat was significantly different by different beef cuts. In conclusion, both wet and dry aging improved the quality of different beef cuts; however, dry aging was more suitable for improving the quality of less preferred beef cuts.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.123-129
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• 1999

Although type 316 stainless steel is widely used such as in reactors of petrochemical plants and pipes of steam power plants and s attracting attention as potential basic material for the fast breeder reactor structure alloys in nuclear power plants and is attracting attention as potential basic material for the fast breeder reactor structure alloys in nuclear power plants the effect of precipitates which form during the long term exposure at service temperature on creep properties is not known sufficiently. In this study to investigate the creep properties and the influence of prior aging on the microstructure to form precipitates specimens were first solutionized at 113$0^{\circ}C$ for 20 minutes and then aged for different times of 0 hr, 100 hrs, 1000 hrs and 2200 hrs at 75$0^{\circ}C$ After heat treatments tensile tests both at room temperature and $650^{\circ}C$ and constant load creep ruptuere tests were carried out.

• Journal of the Korean Graphic Arts Communication Society
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• v.30 no.3
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• pp.13-21
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• 2012

This study was carried out to evaluate the stability of archival documents produced using papers. The properties of archival documents depend on the type of fillers of papers that are used such as fiber, non cellulose fiber, and mineral. The physio-chemical characteristics of archival documents were analyzed by employing acid hydrolysis against cellulose fiber substances. Fibers of Korean hand-made (Hanji), flex, and cotten papers showed higher pH and the degree of polymerization (DP) than wood fiber and mechanical fiber. Mechanical pulp containing 12.8% of lignin showed the greatest decrease of DP due to acid hydrolysis, and this resulted in increase of degree of aging. The filler found to clay and talc did not contain metal such as $Fe^{+2}$, $Fe^{+3}$, and $Cu^{+2}$. The alkaline metals such as Mg, Ca, and Ti showed greater resistance to acid hydrolysis.

• Elastomers and Composites
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• v.3 no.1
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• pp.32-38
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• 1968

The physical properties of NR-SBR and NR-BR blends were studied. 1. In blending, tensile strength decreased with increase in synthetic rubber contents. It was most effective when the ratio of NR/Syn. R is 75/25. 2. Tensile strength decreased with order of NR, SBR and BR and modulus after aging is proportional of synthetic rubber contents. 3. Elongation is less influenced by synthetic rubber ratio that on the other hand, the decrease of elongation is proportional to synthetic rubber contents after aging. 4. Hardness decreased with increase in the synthetic rubber contents and on the other hand, the hardness increased after aging.