• 제목/요약/키워드: Aging heat treatment

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Effect of Oxygen Content on Aging Properties of Ti-39Nb-6Zr alloy (Ti-39Nb-6Zr 합금의 산소함량에 따른 시효특성 변화)

  • Han, Chan Byeol;Lee, Dong-Geun
    • Journal of the Korean Society for Heat Treatment
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    • v.35 no.2
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    • pp.88-95
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    • 2022
  • Titanium alloy for bio-medical applications have been developed to reduce the toxicity of alloying elements and avoid the stress-shielding effect which is caused by relatively high elastic modulus compared to bone. Ti-39Nb-6Zr (TNZ40) alloy of elastic modulus exhibits around 40 GPa in the case of beta single phase. However, the strength of this alloy is lower than the other types of titanium alloys. Many research found that adding oxygen to beta-titanium alloys is beneficial for improving the strength through solid solution strengthening. In this study, TNZ40 ingots with addition of O were prepared by an arc remelting process (Ti-39Nb-6Zr-0.16O (wt.%), Ti-39Nb-6Zr-0.26O (wt.%)). Thermo-mechanical processing (i.e., heat treatment, cold swaging and aging heat treatment) has been performed under various conditions. Therefore, the aim of this study is to investigate the effect of oxygen content and ω phase formation on microstructure and mechanical properties.

Damping Capacity of Heat-Treated Mg-Nd Alloy (열처리한 Mg-Nd 합금의 진동감쇠능)

  • Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.26 no.4
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    • pp.185-190
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    • 2013
  • Influence of solution treatment (T4) and peak-aging (T6) on damping capacity was investigated in permanent-mold cast Mg-3%Nd alloy. In as-cast state, the microstructure was characterized by eutectic $Mg_{12}Nd$ intermetallic phase network in the intergranular region. T4 treatment resulted in a dissolution of the eutectic particles, but small amount of the particles still remained in the microstructure. After T6 treatment, nano-sized ${\beta}^{\prime}(Mg_{12}Nd)$ particles were precipitated within the matrix. T4 microstructure showed higher damping capacity than as-cast and T6 ones. In view of the microstructural features, this may well be associated with the dissolution of second-phase particles which play a role in pinning the dislocations acting as a damping source.

Mechanical and Physical Property Changes of Cu-Ni-Si-Sn-Fe-P Copper Alloy System According to the Heat Treatment Conditions (열처리조건에 따른 Cu-Ni-Si-Sn-Fe-P 석출경화형 동합금계의 물성변화 특성)

  • Kim, Seung-Ho;Yum, Young-Jin
    • Journal of the Korean Society for Heat Treatment
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    • v.26 no.5
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    • pp.225-232
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    • 2013
  • The influence of aging treatment, addition elements and rolling reduction ratio on the microstructure, mechanical, electrical and bendability properties of Cu-Ni-Si-P-x (x = Fe, Sn, Zn) alloys for connector material application was investigated. SEM/EDS analysis exhibited that Ni2-Si precipitates with a size of 20~100 nm were distributed in grains. Fe, Sn, Zn elemnets in Cu-Ni-Si-P alloy imporved the mechanical strength but it was not favor in increasing of electrical conductivity. As higher final rolling reduction ratio, the strength and electrical conductivity is increased after aging treatment, but it indicated excellent bendability. Especially, Cu-2Ni-0.4Si-0.5Sn-0.1Fe-0.03P alloy show the tensile strength value of 700MPa and the electrical conductivity was observed to reach a maximum of 40%IACS. It is optimal for lead frame and connector.

Dependence of Damping Capacity on ${\beta}$ Phase Precipitation in Mg Alloy (Mg 합금에서 진동감쇠능의 ${\beta}$상 석출 의존성)

  • Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.20 no.6
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    • pp.306-310
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    • 2007
  • Changes in microstructure and damping capacity with aging time for solutionized Mg-Al alloy have been investigated. Discontinuous ${\beta}\;(Mg_{17}Al_{12})$ precipitates form along the primary grain boundaries, the amount of which increases as the aging time increases. The hardness of the matrix with respect to aging time shows a typical "S" shape, indicating a generation of fine continuous precipitates in the matrix during the aging. The peak level of damping capacity is obtained after 1 hour of aging, over which the damping capacity becomes deteriorated continuously. The formation of optimum density of continuous ${\beta}$ precipitates with fine morphology which would act as pinning points for dislocation lines, might be responsible for the improvement of damping capacity.

Mechanical Properties of Forged Nimonic 80A Superalloy Fabricated by Vacuum Spray Casting (진공분무주조법에 의해 제조한 Nimonic 80A 초내열합금 단조재의 기계적 특성)

  • Lee, Yun-Soo;Hyun, Soong-Keun;Jung, Dae-Hyun;Byun, Joong-Sig
    • Korean Journal of Metals and Materials
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    • v.50 no.4
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    • pp.263-270
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    • 2012
  • This study investigates the effect of heat treatment on the mechanical properties of a forged Ni-based superalloy called Nimonic 80A. Nimonic 80A ingot samples were fabricated by vacuum spray casting to achieve a fine and homogenized microstructure. The ingot samples were subsequently hot-forged with the diameter of 220 mm at 1373 K. From the center to the surface of the forged Nimonic 80A, its average grain size decreased and its micro-Vickers hardness increased slightly. Solution treatment was carried out at 1353 K with 8 hours of air cooling followed by aging treatment, which was carried out in the range of 873-1073 K with various times from 0.5 to 256 hours. To set the optimum aging conditions, micro-Vickers hardness tests were performed. The maximum hardness value of 388.0 Hv was obtained by aging at 973 K for 32 hours. Also, tensile tests were performed for optimum aging conditions at room temperature and 873 K. The results can be used effectively to perform reasonable heat treatment of Nimonic 80A superalloy.

Effect of Aging Treatment on the Microstructure and Mechanical Properties of Mg-6Al-xZn (x : 1.5, 2.5) Alloys Fabricated by Squeeze Casting (용탕단조된 Mg-6Al-xZn (x=1.5, 2.5) 합금(合金)의 미세조직 및 기계적 성질에 미치는 시효의 영향)

  • Kim, Soon Ho
    • Journal of the Korean Society for Heat Treatment
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    • v.12 no.1
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    • pp.1-8
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    • 1999
  • This study has investigated the effect of aging treatment on the microstructure and mechanical properties of Mg-6Al-xZn(x = 1.5, 2.5) alloys fabricated by the squeeze casting process. The microstructures of as-squeeze cast were composed of pro-eutectic ${\alpha}$, super saturated ${\alpha}$ and ${\beta}(Mg_{17}Al_{12})$ compound. Aged at both $200^{\circ}C$ and $240^{\circ}C$, Mg-6Al-xZn alloys showed the peak hardness due to the formation of ${\beta}(Mg_{17}Al_{12})$ precipitates. The discontinuous precipitates of the lamella type are predominant at $200^{\circ}C$ aging treatment, while the finely dispersed continuous precipitates were dominant at $240^{\circ}C$ aging treatment. Mg-6Al-xZn alloys fabricated by the squeeze casting process had the better combination of tensile strength and elongation compared to the conventionally cast alloys. As zinc contents increased, the tensile strength was increased by the solid solution strengthening effect of zinc.

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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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Changes in Mechanical Properties according to Solid Solution Treatment of Cu-1.6%Co-0.38%Si Alloy (Cu-1.6%Co-0.38%Si 합금의 용체화처리에 따른 기계적 성질의 변화)

  • Kwak, Wonshin;Lee, Sidam
    • Journal of the Korean Society for Heat Treatment
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    • v.33 no.6
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    • pp.277-283
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    • 2020
  • Cu-Co-Si based alloy has a strengthening mechanism for Co2Si intermetallic compounds deposited on the copper matrix after aging treatment and the solution treatment has a key influence on the strength and electrical conductivity of the final products. In this paper, the Cu-1.6%Co-0.38%Si alloy was fixed at the time and the solution treatment temperature was set at a temperature in the range of 800 to 950℃, and the change in mechanical properties was observed by fixing the temperature at 950℃ and changing the time. The microstructure was observed using an electron microscope and an optical microscope, and the changes in hardness, electrical conductivity, and bending workability after aging treatment were investigated. When the solution treatment time is less than 20 seconds, the solution treatment is not sufficient and the formation of precipitates contributing to the increase in hardness decreases and the hardness decreases after the aging treatment, and in more than 50 seconds, the hardness decreases due to the coarsening of the grains and the bending workability got worse.

Effects of Cr content and Thermomechanical Treatment on Tensile Strength and Electrical Conductivity of Cu-Cr Alloys (Cu-Cr 합금의 인장강도와 전기전도도에 미치는 Cr 첨가량 및 가공열처리의 영향)

  • Kim, Ki-Tae;Jung, Woon-Jae;Shin, Han-Chul;Choi, Chong-Sool
    • Journal of the Korean Society for Heat Treatment
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    • v.14 no.1
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    • pp.17-21
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    • 2001
  • The effects of Cr content above its solubility limit and thermomechanical treatment on tensile strength and electrical conductivity of Cu-Cr alloys were studied to obtain optimum Cr content exhibiting a high tensile strength without degradation of electrical conductivity. The increase in Cr content above the solubility limit increased tensile strength of Cu-Cr alloys without deterioration of the electrical conductivity. The electrical conductivity was not affected by cold rolling. The electrical conductivity of a Cu-3.5%Cr alloy subjected to cold rolling ${\rightarrow}$ aging treatment ($450^{\circ}C{\times}1hr$) ${\rightarrow}$ cold rolling was equal to that of the alloy subjected to cold rolling ${\rightarrow}$ aging treatment. However, the tensile strength of the alloy subjected to the former thermomechanical treatment was superior to that of the alloy subjected to the latter thermomechanical treatment at all the deformation degrees.

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The softening behavior of Mg-Li-Al(-Zr) alloys (Mg-Li-Al(-Zr) 합금의 연화현상)

  • Kim, Y.W.;Kwang, Y.H.;Lim, Y.J.;Kim, D.H.;Hong, C.P.
    • Journal of the Korean Society for Heat Treatment
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    • v.11 no.1
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    • pp.10-16
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    • 1998
  • The softening behavior of squeeze cast Mg-Li-Al and Mg-Li-Al-Zr alloys have been investigated. The highest hardness values of Mg-Li-Al and Mg-Li-Al-Zr alloys were obtained after solution treatment at $400^{\circ}C$ for 1 hour. The hardness value, however, decreased as the aging temperature and time increased. Microstructural and calorometric analyses showed that quenched-microstructure changed from primary (${\alpha}$ and ${\beta}$)+secondary ${\alpha}$ to primary(${\alpha}$ and ${\beta}$)+secondary ${\alpha}+{\theta}$ after aging. The softening during aging was due to the coarsening of ${\theta}$ precipitates.

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