• Title/Summary/Keyword: ageing hardening

Search Result 22, Processing Time 0.037 seconds

Physical Property and Phase Transformation in a Commercial Dental Casting High Gold Alloy (시판치과주조용 고금합금의 물리적 성질 및 상변태)

  • Lee, Hee-Kyung;Park, Myoung-Ho;Lee, Hwa-Sik
    • Journal of Technologic Dentistry
    • /
    • v.28 no.1
    • /
    • pp.27-41
    • /
    • 2006
  • The physical property and phase transformation in a commercial dental casting high gold alloy was investigated as a function of ageing temperature and time using microvickers hardness tester, X-ray diffraction, optical and electron microscopy and EPMA analyser. 1. With increasing ageing time, the hardness of solution-treated gold alloys increased slowly at the initial stage of ageing treatment at an ageing temperature of $300{\sim}400^{\circ}C$, and it reached a maximum value of hardness at the medium stage. Finally, it decreased gradually during further ageing. The maximum value of hardness at was similar with that of the conventional materials and suitable for using as the crown & bridge. 2. During isothermal ageing at a temperature range of $300{\sim}400^{\circ}C$, three phases consisting of the Au-rich ${\alpha}_1$phase with a face-centered cubic structure, the Pt3Zn ${\alpha}_2$phase with an ordered AuCu3(L12) type(f.c.c.) and the Pt-rich ${\alpha}_3$phase with face-centered cubic structure in solution-treated gold alloys were transformed into different three phases consisting of the ${\alpha}_1$phase, the ${\alpha}_3$phase and the PtZn $\beta$phase with an ordered AuCu I(L10) type. 3. The hardening of gold alloys was attributed to the lattice strains of the matrix resulting from the transformation of the ${\alpha}_2$phase to the $\beta$phase. 4. The softening of gold alloys during over-ageing was attributed to the coarsening of the nodules consisting of the $\beta$phase and ${\alpha}_1$matrix.

  • PDF

A Study on the Ageing Behavior of Cu-bearing HSLA steels by thermal analysis (열분석법에 의한 Cu를 함유한 HSLA강의 시효 거동에 관한 연구)

  • 박태원;심인옥;김영우;강정윤
    • Proceedings of the KWS Conference
    • /
    • 1994.05a
    • /
    • pp.44-47
    • /
    • 1994
  • The ageing behavior of Cu-bearing HSLA steels was studied by using Differential scanning calorimetry(DSC), Transmission electron microscopy and hardness tester. Two heat evolution peaks were observed during DSC scans over the temperature range of 25~590$^{\circ}C$ at a heating rate of 5$^{\circ}C$/min. The peaks appeared in low (241∼319$^{\circ}C$ : HSLA-A, 224∼310$^{\circ}C$ : HSLA-B) and high temperature (514∼590$^{\circ}C$ : HSLA-A, 451∼558$^{\circ}C$ : HSLA-B) are attributed to the formation of coherent Cu-clusters and noncoherent $\varepsilon$-Cu phase, respectively. It was confirmed that as ageing proceeds, the coherent bcc Cu-clusters transform to noncoherent fcc $\varepsilon$-Cu phase. In the case of the ageing to peak hardness at 300$^{\circ}C$ and 400$^{\circ}C$, the coherent Cu-clusters contributed to the hardening. As ageing time and temperature increase over peak hardness, noncoherent $\varepsilon$-Cu are formed and hardness decreases.

  • PDF

Aging model for Al-Mg-Si forged part (Al-Mg-Si 단조품의 시효 모델)

  • Kwon Y.-N.;Lee Y.-S.;Lee J.-H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2005.05a
    • /
    • pp.307-310
    • /
    • 2005
  • Ageing behavior of the Al-Mg-Si alloy was modeled for the use of optimization of Al forging product. Typical precipitates of Al-Mg-Si alloy are a wide variety of metastable phases (e.g. GP zones, $\beta',\beta'$). These rod shaped particles take a role to hinder the dislocation movement. The precipitation sequence in Al-Mg-Si alloys is quite complex and the strength of precipitate particles differs with the ageing condition. In the present study, the ageing behavior of Al-Mg-Si alloy was investigated by using an industrial grade Al 6061 alloy forged product, which was a perform for an Al impeller for turbo charger. The precipitate hardening models by Esmaeili's approach were used for the analysis of ageing behavior.

  • PDF

Effects of Fe and Si Additions on the Ageing Behaviors for High Strength Al-Cu-Mn-Ti-Zr-Cd Casting Alloys (Fe과 Si의 첨가가 주조용 고강도 Al-Cu-Mn-Ti-Zr-Cd 합금의 시효경화거동에 미치는 영향)

  • Kim, Chul-Hyo;Lee, Jeong-Moo;Kim, Kyung-Hyun;Kim, In-Bae
    • Journal of Korea Foundry Society
    • /
    • v.24 no.1
    • /
    • pp.45-51
    • /
    • 2004
  • Fe and Si are common impurity elements in the aluminum alloys. In this investigation, the effects of the addition of Fe and Si on the age-hardening behaviors of the Al-Cu-Mn-Ti-Zr-Cd casting alloys were examined through hardness measurements, calorimetric techniques and observation of the transmission electron microscopy. The addition of Fe depresses the formation of GPII and ${\theta}'$, and thus retards the peak aging time and reduces the peak hardness of the Al-Cu-Mn-Ti-Zr-Cd alloys. On the contrary, the addition of Si accelerates the formation of GPII and ${\theta}'$ and thus accelerates age-hardening behaviors of the Al-Cu-Mn-Ti-Zr-Cd alloys.

Effect of Porosity on Quality Index of Tensile Property of A356 Casting Alloys (A356합금의 품질지수에 미치는 미소기공율의 영향)

  • Lee, Choong-Do
    • Journal of Korea Foundry Society
    • /
    • v.38 no.5
    • /
    • pp.95-102
    • /
    • 2018
  • The dependence of the tensile properties on variations in the porosity of A356 aluminium alloys was investigated in terms of the quality index of the tensile properties based upon the ultimate tensile strength and elongation as well as the variation of the strength coefficient and strain-hardening exponent with regard to a T6 treatment. The test specimens were prepared by low-pressure die-casting and a subsequent T6 treatment, and the experimental results of a tensile test carried out at room temperature were compared to the theoretical description using a modified constitutive model. The nominal value of the quality index of A356 alloys increases gradually with a lapse of the ageing time upon a T6 treatment, despite the fact that this value is temporarily decreased during the initial stage of ageing from a solutionised condition. Additionally, the quality index depends practically upon the porosity variation with a power law relationship without regard to whether in solutionised or artificial aged conditions. The theoretical description indicates that the strength coefficient directly determines the nominal level of the quality index. Moreover, the overall dependence of the quality index on the porosity variation is remarkably weakened with an increase in the tensile strain, whereas the quality index depends sensitively upon the porosity variation with a low value of the strain-hardening exponent.

Age Hardening and Mechanical Property of Extruded Al-Zn-Mg-(Cu) Al Alloys with Sc addition (Sc 첨가된 Al-Zn-Mg-(Cu)계 알루미늄 합금 압출재의 시효 경화 거동과 기계적 성질)

  • Shim, Sung Yong;Lim, Su Gun
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.20 no.5
    • /
    • pp.243-249
    • /
    • 2007
  • The age hardening behavior and mechanical properties of an extruded Al-Zn-Mg-(Cu)-0.1 wt.%Sc alloy were investigated with the Sc addition and ageing temperature. The results showed that the $Al_3Sc$ compounds were formed by Sc addition and distributed preferentially along the extrusion direction. The age hardening of Al-Zn-Mg-Cu-0.1 wt.%Sc alloy which was treated by T6 process was more significant than that of Al-Zn-Mg-0.1 wt.%Sc alloy. The tensile property of Al-Zn-Mg-Cu+0.1 wt.%Sc alloy was also higher than that of Al-Zn-Mg-0.1 wt.%Sc alloy, which is 691 MPa and 584 MPa in strength and 9% and 11% in elongation, respectively.

The Effect of the Heating Conditions on the Warm Hydro-Formability of the Alumium Alloys (알루미늄합금의 열간 액압성형법 성형성에 대한 가열조건의 영향도 분석)

  • Kim, Bong-Joon;Park, Kwang-Su;Ryu, Jong-Soo;Son, Sung-Man;Moon, Young-Hoon
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.18 no.3
    • /
    • pp.172-176
    • /
    • 2005
  • Modern automobiles are built with a steadily increasing variety of materials and semifinished products. The traditional composition of steel sheet and cast iron is being replaced with other materials such as aluminum and magnesium. But low formability of these materials has prevented the application of the automotive components. The formability can be enhanced by conducting the warm hydroforming using induction heating device which can raise the temperature of the specimen very quickly. The specimen applied to the test is A6061, A7075 extruded tubes which belong to the age-hardenable aluminum alloys. But in the case of A6061 age hardening occurs at room temperature or at elevated temperatures before and after the forming process. In this study the effects of the heating condition such as heating time, preset temperature, holding time during die closing and forming time on the hydroformability are analyzed to evaluate the phenomena such as dynamic strain hardening and ageing hardening at high temperatures after the hydroforming process.

Effect of cooling rate on the microstructure and impact toughness of Cu-bearing HSLA steels (Cu를 함유한 HSLA강의 미세 조직과 인성에 미치는 냉각 속도의 영향)

  • 박태원;심인옥;김영우;강정윤;박화순
    • Journal of Welding and Joining
    • /
    • v.13 no.2
    • /
    • pp.122-131
    • /
    • 1995
  • The effects of cooling rate on the microstructures, precipitation of Cu-cluster, .epsilon.-Cu and impact toughness of high strength low alloy(HSLA) steel were studied using hardness tester, impact tester, DSC(differential scanning calorimetry), AES(auger electron spectroscopy) and TEM(transmission electron microscopy). Not only the Cu-precipitates but also the segregation of Cu, As, Sb, P, S, N, Sn along grain boundary were not observed at the specimens heat treated from 800.deg. C to 300.deg. C with the cooling time of 12-125 sec. The Cu-cluster, .epsilon.-Cu are formed by introducing ageing after cooling and the effect of precipitates on hardening increase after cooling was the same in all cooling rate. The peak hardness was obtained at an ageing of 500.deg. C in all cooling conditions. The impact energy become higher as the cooling time increases. This fact can be explained to be due to the tempering effect applied on the cooling stage since the present alloy has a relatively high Ms temperature and the local high concentration of the retained austenite.

  • PDF

The Analysis of the Oxidation Index of Korea Traditional Paper(Hanji) Which Is Used as the Rrestoration Paper of the Waxed Volume in the Annals of Joseon Dynasty (조선왕조실록 밀랍본 복원용지로서 전통한지의 oxidation index 분석)

  • Seo, Jin-Ho;Jeong, So-Young;Jeong, Seon-Hwa
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.40 no.1
    • /
    • pp.55-61
    • /
    • 2008
  • The annals of Joseon Dynasty is the most valuable resource containing the record of Korean history and has been known as one of the UNESCO's Memory of the World Register. In some period, wax-treated paper was used in the annals of Joseon Dynasty to prevent the damage from pests. But, wax-treated volumes were discolored to brown, white or black, and partially cracked by the stiffened wax. It means that wax-treated volumes were damaged by the hardening and oxidizing of wax. The wax is considered as the first reason in damages on the wax-treated volume. Therefore, in this study we analysed the oxidation index of Korea traditional paper(Hanji) which is used as the restoration paper of the waxed volume in the annals of Joseon Dynasty by using FT-IR. As the analysis of FT-IR, the traditional two-layed stamping paper (Hanji sample F), which was treated by starch in its surface, was shown the most stable state after the accelerated ageing test.