• Title/Summary/Keyword: Solution Heat-treatment

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The Study of Corrosion Behavior for Solution and Aging Heat Treated Ti alloy (Ti 합금의 용체화열처리와 시효열처리에 따른 부식거동)

  • Baik, Shin-Young
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.22 no.1
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    • pp.138-144
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    • 2016
  • Titanium is resistant to general corrosion and in sea water because of the passivity layer film on the surface of material, but may be attacked by environments that cause breakdown of the protective oxide layer including hydrochloric, sulfuric and phosphoric acids. In this study, the Ti alloys were solution heat treatment 5hours at $1066^{\circ}C$ and $966^{\circ}C$, and followed by aging heat treated, 1, 4, 8 and 16 hours in $500^{\circ}C$, $600^{\circ}C$ and $650^{\circ}C$ respectively. The heat treated specimens were measured micro Vicker's hardness, and then accomplished electrochemical polarization test for comparing corrosion in 1N sulfuric acid solution. Additionally, micro structures were taken for corrosion tested specimens. The results showed that corrosion resistance was higher in solution heat treated alloy than base and age heat treated metal. Measured corrosion resistants were increased as increasing aging heat treatment time and temperature.

Evaluation of the Characteristics of the Aluminum Alloy(AC8A) Casting Material by Heat Treatment(II) (AC8A 알루미늄 합금 주조재의 열처리에 의한 특성 평가(II))

  • Moon, Kyung-Man;Jeong, Jae-Hyun;Lee, Myeong-Hoon;Baek, Tae-Sil
    • Journal of Power System Engineering
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    • v.20 no.5
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    • pp.29-36
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    • 2016
  • Aluminum alloys have been widely used in engine materials, cold & hot-water storage vessels and piping etc., Furthermore, the aluminum alloy of AC8A have been widely used in mold casting material of engine piston for various vehicles because of its properties of temperature, wear and corrosion resistance. Therefore, it is considered that evaluation of corrosion resistance as well as wear resistance of AC8A material is also important to improve its property and to prolong its lifetime. In previous paper, the effect of solution($510^{\circ}C$:4hrs) and tempering($190^{\circ}C$: 16, 24, and 36 hrs)heat treatments to corrosion resistance and hardness were investigated using electrochemical method. In this study, in order to examine completely the effect of the tempering hours to hardness variation and corrosion resistance, the results of solution($510^{\circ}C$:4hrs) and tempering($190^{\circ}C$: 2, 4, 8 and 12hrs)heat treatments to hardness and corrosion resistance were investigated using electrochemical method. The hardness decreased with solution heat treatment compared to mold casting condition, but its value increased with tempering heat treatment. Furthermore, the corrosion resistance increased with decreasing of the hardness, and decreased with increasing of the hardness reversely. And the tempering heat treatment temperature at $190^{\circ}C$ for 8 hrs exhibited the highest value of the hardness and also indicated the highest corrosion current density. However, the values of hardness and corrosion current density was again increasingly decreased with increasing of tempering hours than 8 hrs, Consequently, it is suggested that decision of the optimum. tempering hours is very important to improve the corrosion or wear resistance.

Effect of Solution-Treatment Temperature on Microstructure and Damping Capacity of a Martensitic Fe-7%Ni-0.4%C Alloy (Fe-7%Ni-0.4%C 마르텐사이트합금의 미세조직과 진동감쇠능에 미치는 용체화처리온도의 영향)

  • Lee, Young-Kook;Jee, Kwang-Koo;Choi, Chong-Sool
    • Journal of the Korean Society for Heat Treatment
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    • v.11 no.1
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    • pp.1-9
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    • 1998
  • The objective of this study is to investigate the effect of solution-treatment temperature on the microstructure and damping capacity of a martensitic Fe-7%Ni-0.4%C alloy. The size of lath increased from $0.3{\mu}m$ to $0.55{\mu}m$ with increasing the solution-treatment temperature from 700 to $1100^{\circ}C$. In addition, the size of block, packet, and austenite grain had tendency to increase with increasing solution-treatment temperature. The damping capacity of the Fe-7%Ni-0.4%C martensitic alloy decreased with increasing the solution treatment temperature. The reason is not attributed to the increase in the size of lath, block, packet, and austenite grain, but to the increase in vacancy concentration which hinders dislocation motion.

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Fabrication of Hydroxyapatite-coated Zirconia by Room Temperature Spray Process and Microstructural Change by Heat-treatment (상온 분사법에 의한 수산화아파타이트 코팅 지르코니아의 제조 및 미세구조에 미치는 열처리 효과)

  • Lee, Jong Kook;Eum, Sangcheol;Kim, Jaehong;Jang, Woo Yang
    • Journal of the Korean Society for Heat Treatment
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    • v.28 no.1
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    • pp.17-23
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    • 2015
  • Hydroxyapatite coatings were fabricated by a room temperature spray method on zirconia substrates and the influence of heat-treatment on their microstructure was also investigated. Phase composition of coated hydroxyapatite films was similar to the starting powder, but the grain size of hydroxyapatite particles was reduced to the size of nano-scale about 100 nm. Grain size, particle compactness, and adhesiveness to zirconia of hydroxyapatite coatings were increased with heat-treatment temperature, but some of cracks by heat-treatment above $1100^{\circ}C$ were initiated between hydroxyapatite coatings and zirconia substrate. Heat-treated hydroxyapatite layers show the dissolution in SBF solution for 5 days. Hydroxyapatite-coated specimen heat-treated at $1100^{\circ}C$ for 1 h has a good biocompatibility, which specimen induced the nanocrystalline hydroxyapatite precipitates on the coating surface by the immersion in SBF solution for 5 days.

Study on the optimum hot forming temperature and solution heat treatment temperature for the super duplex stainless steel weld (수퍼 이상 스테인리스강 용접부의 최적 열간 성형온도 및 용체화 열처리 온도에 관한 연구)

  • Ji Chun-Ho;Choi Jun-Tae;Kim Dae-Sun
    • Proceedings of the KWS Conference
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    • 2006.05a
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    • pp.137-139
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    • 2006
  • In order to establish the optimum hot forming temperature and solution heat treatment temperature for 25% chromium super duplex stainless steel weld, a commercial 25%Cr-10%Ni-4%Mo weld metal for super duplex stainless steel(UNS S32750) with different solution heat treatment conditions at $1100^{\circ}C,\;1050^{\circ}C,\;1025^{\circ}C\;and\;1000^{\circ}C$ for 1.5 hours has been investigated by means of optical metallography, and estimated mechanical properties. It is found that exposure to elevated temperatures at $1050^{\circ}C,\;1025^{\circ}C\;and\;1000^{\circ}C$ except $1100^{\circ}C$ brings partial decomposition of ferrite to austenite and sigma phase, which deteriorates their properties and heat treatment at $1100^{\circ}C$ shows acceptable mechanical properties.

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Effect of Alkali and Heat Treatments of Ti-6Al-4V Alloy on the Precipitation of Calcium Phosphate (Ti-6Al-4V 합금의 알칼리 및 열처리가 인산칼슘 침착에 미치는 영향)

  • Park, Jae-Han;Lim, Ki-Jung;Kim, Sang-Mok;Kim, Byung-Ock;Han, Kyung-Yoon
    • Journal of Periodontal and Implant Science
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    • v.30 no.1
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    • pp.187-203
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    • 2000
  • The precipitation of calcium phosphate on implant surface has been known to accelerate osseointegration and to enhance osseous adaptation. The present study was performed to examine whether the precipitation of calcium phosphate on Ti-6Al-4V alloy could be affected by the immersion in NaOH solution and heat treatment. Ti-6Al-4V alloy plates of $15{\times}3.5{\times}1mm$ in dimension were polished sequentially from #240 to #2,000 emery paper and one surface of each specimen was additionally polished with $0.1{\mu}m$ alumina paste. Polished specimens were soaked in various concentrations of NaOH solution(0.1, 1.0, 3.0, 5.0, 7.0, 10.0 M) at $60^{\circ}C$ for 24 hours for alkali treatment, and 5.0 M NaOH treated specimens were heated for 1 hour at each temperature of 400, 500, 600, 700, $800^{\circ}C$. After the alkali and heat treatments, specimens were soaked in the Hank's solution with pH 7.4 at $36.5^{\circ}C$ for 30days.The surface ingredient change of Ti-6Al-4V alloy was evaluated by thin-film X-ray diffractometer(TF-XRD) and the surface microstructure was observed by scanning electron microscope(SEM), and the elements of surface were analyzed by X-ray photoelectron spectroscopy(XPS). The results were obtained as follows ; 1. The precipitation of calcium phosphate on Ti-6Al-4V alloy was accelerated by the immersion in NaOH solution and heat treatment. 2. In Alkali treatment for the precipitation of calcium phosphate on Ti-6Al-4V alloy, the optimal concentration of NaOH solution was 5.0 M. 3. In heat treatment after alkali treatment in 5.0 M NaOH solution, the crystal formation on alloy surface was enhanced by increasing temperature. In heat treated alloys at $600^{\circ}C$, latticed structure and prominences of calcium phosphate layer were most dense. On heat treated alloy surface at the higher temperature(${\geq}700^{\circ}C$), main crystal form was titanium oxide rather than apatite. The above results suggested that the precipitation of calcium phosphate on the surface of Ti-6Al-4V alloy could be induced by alkali treatment in 5.0 M-NaOH solution and by heat treatment at $600^{\circ}C$.

Changes of Microstructures and Mechanical Properties of Recycled AC2B Alloy Chip Fabricated by Solution Heat Treatment (재활용 절삭칩으로 제조된 AC2B 합금의 용체화 열처리에 따른 미세조직 및 기계적특성 변화)

  • Kim, Dong-Hyuk;Yoon, Jong-Cheon;Choi, Chang-Young;Choi, Si-Geun;Hong, Myoung-Pyo;Shin, Sang-Yoon;Ye, Byung-Joon
    • Journal of Korea Foundry Society
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    • v.38 no.2
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    • pp.32-40
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    • 2018
  • Changes in the microstructures and mechanical properties of an AC2B alloy through solution heat treatment were investigated using recycled AC2B cutting chips as raw material. The as-cast microstructure of the AC2B alloy comprised ${\alpha}$-Al, $Al_2Cu$, and coarse needle-shaped phases considered to be eutectic Si and an Al-Fe-Si based intermetallic compound. After solution heat treatments at $505^{\circ}C$ for 1 h and 6 h, the samples showed complete dissolution of $Al_2Cu$ and relatively fine distribution of intermetallic compounds. Hardness test results showed that the hardness rapidly increased after the solution heat treatment for 1 h by solid solution hardening, and the increase of hardness exhibited a plateau from 1 h to 6 h. The results of the hardness and tensile tests showed that there was no visible difference in the effect of 1 h and 6 h solid solution treatment.

Hardness and Electrical Conductivity Changes according to Heat Treatment of Cu-1.6Co-0.38Si Alloy (Cu-1.6Co-0.38Si 합금의 열처리에 따른 경도 및 전기전도도의 변화)

  • Kwak, Wonshin;Lee, Sidam
    • Journal of the Korean Society for Heat Treatment
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    • v.33 no.5
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    • pp.226-231
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    • 2020
  • The Cu-Co-Si alloy shows high strength by forming precipitates by aging precipitation heat treatment of supersaturated solid solution treated with solution treatment such as Cu-Ni-Si alloy, and the Co2Si precipitated phase is dispersed in the copper matrix. The effect of aging treatment on the microstructure, mechanical and electrical properties of Cu-Co-Si alloys for electronic devices was investigated. As a results of SEM/EDS analysis, it was found that Co2Si precipitates of 30~300 nm size were distributed in grains. By performing the double aging treatment, it was possible to improve the strength and electrical conductivity by dispersing the fine precipitate evenly.

Effect of Heat Treatment on the Martensitic Transformation and Tensile Deformation Behavior in Ti-Ni-B shape Memory Alloy (Ti-Ni-B 형상기억합금의 마르텐사이트변태 및 인장변형거동에 미치는 열처리의 영향)

  • Lee, O.Y.;Park, Y.K.;Ahn, H.K.
    • Journal of the Korean Society for Heat Treatment
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    • v.8 no.1
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    • pp.75-83
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    • 1995
  • The purpose of this study is to investigate the effect of heat treatments on the martensite transformation and tensile deformation behavior in Ti-Ni-B alloys with various boron concentration. Three types of heat treatment are given to the specimens; i) solution treatment ii) aging iii) thermo-mechanical treatment. In solution treated specimens. R-phase transition which is related to abnormal increase of electrical resistance prior to martensitic transformation has been formed at a boron content of 0.2at % and the $M_s$ temperature has been decreased with the increasing of boron content. However. It has not been affected by aging, while that of thermo-mechanically treated specimens has been remarkably increased in the vicinity of recrystallization temperature. The thermo-mechanically treated specimen has showed a good thermal fatigue characteristics, shape memory effect and superelasticity in comparison with the solution treated specimen.

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Strain Amplitude Dependence of Damping Capacity in Mg-AI-Si Alloy (Mg-Al-Si 합금에서 진동감쇠능의 변형진폭 의존성)

  • Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.24 no.3
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    • pp.144-148
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    • 2011
  • Change in damping capacity with strain amplitude was studied in Mg-Al-Si alloy in as-cast, solution-treated and aged states, respectively. The as-cast microstructure of the alloy is characterized by eutectic ${\beta}$($Mg_{17}Al_{12}$) phase and Chinese script type $Mg_2Si$ particles. The solution treatment dissolved the ${\beta}$ phase into the matrix, while the aging treatment resulted in the distribution of continuous and discontinuous type ${\beta}$ precipitates. The solution-treated microstructure showed better damping capacity than as-cast and aged microstructures both in strain-dependent and strain-independent damping regions. The decrease in second-phase particles which weakens the strong pinning points on dislocations and distribution of solute atoms in the matrix, would be responsible for the enhanced damping capacity after solution treatment.