• Title/Summary/Keyword: Aging Heat-Treatment

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Effects of Ca, Si on the Microstructure and Aging Characteristic of AZ91 Alloy (AZ91합금의 조직(組織)과 시효특성(時效特性)에 미치는 Ca 및 Si의 영향(影響))

  • Jhee, T.G.;Kim, Y.K.
    • Journal of the Korean Society for Heat Treatment
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    • v.15 no.6
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    • pp.260-268
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    • 2002
  • The effects of calcium and silicon on microstructure and aging characteristics of AZ91 magnesium alloy during T5 treatment was investigated. The addition of 0.88% calcium or 0.25% silicon to AZ91 alloy made dendrite cell smaller. Especially, silicon is more effectively acted as refinement of the dendrite cell than calcium. It is due to that $Mg_2Si$ precipitated at the dendrite cell boundary or in the matrix during T5 treatment of Si added AZ91 alloy retarded the growth of the secondary phase. In the mean while, without inducing the precipitates containing calcium, calcium was segregated mainly around secondary phase such as $Mg_{17}Al_{12}$ and partially dissolved in ternary eutectic (Mg-Al-Ca) structure. In the AZ91 alloy containing both silicon and calcium, more finely distributed $Mg_2Si$ in matrix homogeneously and much finer microstructure were obtained than those containing silicon or calcium. Hence, An AZ91 containing both silicon and calcium was more effective to retarding the growth of the secondary phase than the other AZ91 alloy such as AZ91 alloy containing silicon or AZ91 alloy containing calcium.

Effect of Aging Treatment on the Microstructures and Mechanical Properties of 7N01 Aluminium Alloy (7N01 Al 합금의 미세조직 및 기계적 성질에 미치는 시효처리의 영향)

  • Hwang, Youn-Gu;Kang, Min-Chul;Kang, Jung-Youn;Kim, In-Bae
    • Journal of the Korean Society for Heat Treatment
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    • v.13 no.2
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    • pp.103-107
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    • 2000
  • Effect of aging treatment on the microstructures and mechanical properties of 7N01 Al alloy was investigated by differential scanning calorimetry, transmission electron microscopy, microhardness measurement and tensile test. Maximum hardness(125.7Hv) and tensile strength(447.3MPa) were obtained from the specimen aged at $120^{\circ}C$ for 32hrs. The major precipitation hardening phase was confirmed as coherent $MgZn_2({\eta}^{\prime})$ phase. Microhardness changes after peakaged condition showed very large decrease upon increased aging time. This result was attributed to the high transformation rate from coherent ${\eta}^{\prime}$ to incoherent ${\eta}$. It was found that the precipitation sequence of 7N01 Al alloy was GP zone${\rightarrow}$metastable spherical hcp $MgZn_2({\eta}^{\prime}){\rightarrow}$ equilibrium rodlike hcp $MgZn_2({\eta})$.

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Effect of aging treatment on the microstructures and mechanical properties of 6N01 Aluminium alloy (6N01 Al 합금의 미세조직 및 기계적 성질에 미치는 시효처리의 영향)

  • Kang, Min-Cheol;Koo, Hung-Suh;Yun, In-Taeg;Kang, Chung-Yun;Kim, In-Bae
    • Journal of the Korean Society for Heat Treatment
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    • v.11 no.4
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    • pp.268-273
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    • 1998
  • Effect of aging treatment on the microstructures and mechanical properties of 6N01 Aluminium alloy was investigated by differential scanning calorimetry, transmission electron microscopy, microhardness measurement and tensile test. It was found that the precipitation sequence of 6N01 Aluminium alloy was GP zone ${\rightarrow}$ metastable hexagonal $Mg_2S_i({\beta}^{\prime})$,${\rightarrow}$ equilibrium fcc $Mg_2S_i({\beta})$, and the precipitates at peak aged condition were GP zones and ${\beta}^{\prime}$ phase. Microhardness changes during over aged condition showed very small decrease upon increased aging time. This result was attributed to the very slow transformation rate of ${\beta}^{\prime}$ to ${\beta}$. Maximum hardness(116 Hv) and tensile strength(312.6MPa) with 22.3% elongation were obtained from the specimen aged at $180^{\circ}C$ for 15hrs.

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Aging Behaviors of a Rapidly Solidified Al-Li-Cu-Mg-Zr Alloy (급냉응고된 AI-Li-Cu-Mg-Zr 합금의 시효거동)

  • Nam, D.H.;Hong, Y.J.;Jeong, H.Y.;Bae, C.H.;Kim, I.B.
    • Journal of the Korean Society for Heat Treatment
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    • v.4 no.2
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    • pp.38-46
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    • 1991
  • Effects of aging treatment on the microstructures and microhardness of a rapidly solidified Al-Li-Cu-Mg-Zr alloy were investigated by differential scanning calorimetry(DSC) and transmission electron microscopy(TEM). The as-melt-spun ribbon was consisted of fine ${\delta}^{\prime}$ and icosahedral intermetallic compound which were precipitated in the matrix. Two exothermic peaks with the range of $120^{\circ}C-190^{\circ}C$ and $280^{\circ}C-344^{\circ}C$ corresponded to ${\delta}^{\prime}$ and ${\theta}^{\prime}$, S', $T_1$ precipitating reaction respectively, and two endothermic peaks with the range of $190^{\circ}C-280^{\circ}C$ and $344^{\circ}C-550^{\circ}C$ corresponded to dissolution of ${\delta}^{\prime}$ and ${\theta}^{\prime}$, S', $T_1$ respectively in DSC curves. Peak hardness value was obtained at $210^{\circ}C$ for 1 hr aging treatment.

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The Effect of Age Heat-treatment to the Electro-Chemical Corrosion Behavior on Ti-6Al-4V (Ti-6Al-4V재의 전기화학적부식 거동에 미치는 시효열처리의 영향)

  • 백신영
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.6
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    • pp.70-77
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    • 2000
  • In this paper, the effect of solution and age heat treatment to the corrosion behavior for the Ti-6Al-4V alloy were studied by cyclic polarization methods. Ti-6Al-4V was solution heat treated at $1,066^{\circ}C$ and $966^{\circ}C$ for 5 hours, and followed by age heat treated at $650^{\circ}C$, $600^{\circ}C$ and $550^{\circ}C$ with 1, 2, 4, 8 and 16 hours under vacuum environment. Test solution was 3.5% NaCl with temperature $25^{\circ}C$. The obtained results were as follows: 1. Base metal was exhibited higher electrical charge than that of solution and aged material. With decrease of solution-treatment temperature from 1066 to $966^{\circ}C$, the electrical charge was increased due to softening of micro structure. 2. The corrosion resistance of specimen that solution treated at $966^{\circ}C$ for 5 hours and age heat treated at 650, 660 and $550^{\circ}C$ were increased with increase of aging time to 4, 8 and 16 hours respectively, and then decreased. 3. In case of 316L stainless steel, measured charge and corrosion potential was 0.0627 coulomb and -614 mV respectively. Corrosion resistance of Ti-6Al-4V was higher than that of 316L.

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Microstructure Evolution of Ti-6Al-4Fe-0.25Si through Aging Heat Treatment (시효처리에 따른 Ti-6Al-4Fe-0.25Si 합금의 미세조직 변화)

  • Song, Yong Hwan;Kang, Joo-Hee;Park, Chan Hee;Kim, Seong-Woong;Hyun, Yong-Taek;Kang, Nam Hyun;Yeom, Jong-Taek
    • Korean Journal of Metals and Materials
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    • v.50 no.7
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    • pp.477-485
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    • 2012
  • The effect of aging heat treatment on microstructure evolution of the Ti-6Al-4Fe-0.25Si alloy with an initial microstructure of an elongated alpha was investigated. Aging treatments of the samples were carried out at $550^{\circ}C$ for up to 100 hours. The microstructure of the 5 hours heat-treated sample consisted of alpha grains, beta matrix and some TiFe intermetallic compounds that were precipitated from the beta matrix. Increasing the aging time to 10 hours, most of the beta matrix was decomposed to very fine alpha grains (${\sim}0.5{\mu}m$) and TiFe, and thus the volume fraction of the beta matrix was significantly decreased. EBSD analysis revealed that newly formed tertiary-alpha-grains in the vicinity of TiFe had high angle boundaries with respect to the primary and secondary alpha grains. As a result of these phase transformations during aging, the fraction of the alpha/alpha grain boundary was increased while that of the alpha/beta phase boundary was decreased.

A Study of Aging Characteristic of EPDM by High-temperature Treatment (고온 열처리에 의한 EPDM의 열화 특성에 대한 연구)

  • Choi, N.H.;Han, S.I.;Han, S.O.;Yoon, J.Y.;Park, K.S.;Kim, J.S.
    • Proceedings of the KIEE Conference
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    • 1997.07d
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    • pp.1465-1468
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    • 1997
  • In this study we investigated the aging characteristic such as leakage current, dielectric loss, contact angle, of EPDM for outdoor use by thermal treatment. And also observed the color change of surface, changing of chemical ingredient of the marterials by optical microscope. SEMI, FTIR and EDX at the section and surface. The test result show that leakage current is increased with thermal aging time. contact angle and dielectric loss is slightly decreased. Moreover, micro-void or crack in bulk is severely increased with aging time. However, the result affect to the tan $\delta$ at bulk of EPDM. It seems that carrier sources are removed by degassing with heat treatment.

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Study on the Microstructure and Mechanical Properties of 17-4PH Stainless Steel Depending on Heat Treatment and Exposure Time (열처리 및 노출시간에 따른 17-4PH 스테인레스강의 미세조직 및 기계적 특성에 관한 연구)

  • Yu, Wi-Do;Lee, Jong-Hun;Im, Yeong-Mok;Yun, Guk-Tae
    • 연구논문집
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    • s.32
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    • pp.77-84
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    • 2002
  • A martensitic precipitation hardening stainless steel, 17-4PH has been widely used in the aircraft, chemical and nuclear industries for long time, owing to the excellent mechanical properties with corrosion resistance that can be achieved by simple heat treatment. The microstructure and mechanical properties of the 17-4PH stainless steel cast parts for aircraft, such as impeller, are largely affected by heat treatment condition. But the database of heat treatment has not been clearly established in the domestic investment casting industries because the domestic aerospace, industry lags behind the advanced countries. In this study, the microstructural evolution and mechanical properties of cast 17-4PH stainless steel depending on the heat treatment conditions and aging at $400^{\circ}C$ were investigated.

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Effect of Aging Heat Treatment on the Mechanical Properties in Inconel 718 Alloy (Inconel 718 합금의 시효열처리가 기계적 성질에 미치는 영향)

  • Kang, Hee Jae;Kim, Jung Min;Jee, Sung Hwan;Sung, Jie Hyun;Kim, Young Hee;Sung, Jang Hyun;Jeon, Eon Chan
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.3
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    • pp.271-277
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    • 2013
  • Inconel 718 super alloy was aging heat treated at the temperature range from $675^{\circ}C$ to $785^{\circ}C$ for 5~40 hours after solution annealing at $1025^{\circ}C$ for 1 hour. The aging treated specimens were investigated microstructure, mechanical properties and thermal expansion/contraction. Precipitates appeared for a long time aging treatment were niobium carbide and also ${\gamma}^{\prime}$ phase. For the aging treatment time of 10 hours, the changes in strength and hardness with increasing aging treatment temperature showed the maximum value at the temperature of $725^{\circ}C$. This maximum value is to be related with the precipitation of ${\gamma}^{\prime}$ and ${\gamma}^{{\prime}{\prime}}$ phases. The decrease in strength, elongation and hardness during long time aging at $725^{\circ}C$ were thought to be induced from the coarsening of the grain size and the transformation of ${\gamma}^{{\prime}{\prime}}$ phase to ${\gamma}^{\prime}$ phase. For the specimens treated for 10 hours, impact energy showed constant value of ~105 J with increasing the aging temperature, however this value continuously decreased with elapsing time at the aging temperature of $725^{\circ}C$. It was found that the decrease in impact value was induced from the coarsening of grain size and the carbide coarsening. The coefficient of thermal expansion of aging treated Inconel 718 alloy increased with raising test temperature, and the coefficient was appeared $11.57{\sim}12.09{\mu}m/m{\cdot}^{\circ}C$ and $14.28{\sim}14.39{\mu}m/m{\cdot}^{\circ}C$, respectively, after heating to $150^{\circ}C$ and $450^{\circ}C$.

Cryogenic fracture behaviors and polarization characteristics according to sensitizing heat treatment on structural material of the nuclear fusion reactor (핵 융합로 구조재료의 예민화 열처리에 따른 극저온 파괴거동 및 분극특성)

  • Kwon, Il-Hyun;Chung, Se-Hi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.2
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    • pp.311-320
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    • 1998
  • The cryogenic fracture behaviors of austenitic stainless steel HN2 developed for nuclear fusion reactor were evaluated quantitatively by using the small punch(SP) test. The electrochemical polarization test was applied to study thermal aging degradation of HN2 steel. The X-ray diffraction(XRD) analysis was conducted to detect carbides and nitrides precipitated on the grain boundary of the heat treated HN2 steel. The mechanical properties of the HN2 steel significantly decreased with increasing time and temperature of heat treatment or with decreasing testing temperature. The integrated charge(Q) obtained from electrochemical polarization test showed a good correlation with the SP energy(ESP) obtained by means of SP tests. From the results observed in the x-ray diffraction and anodic polarization curve, it was known that the material the grain boundary. Combining SP test and electrochemical polarization test, it could be useful tools to non-destructively evaluate the cryogenic fracture behaviors and the aging degradation for cryogenic structural material.