• Title, Summary, Keyword: Al-alloy

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Characteristics of Plasma Electrolytic Oxide Coatings on Mg-Al Alloy with Coating Time (피막처리 시간에 따른 Mg-Al 합금의 플라즈마 전해 산화 피막 특성)

  • Lee, Du-Hyung;Kim, Bo-Sik;Chang, Si-Young
    • Korean Journal of Materials Research
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    • v.18 no.5
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    • pp.241-246
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    • 2008
  • Pure Mg and Mg-6wt.%Al alloy were coated by the plasma electrolytic oxidation with various coating times and the microstructural and mechanical characteristics of the coatings were investigated. The coatings on pure Mg and Mg-6wt.%Al alloy consisted of MgO and $Mg_2SiO_4$. The surface roughness and thickness of the coatings became larger as the coating time increased. The coatings on the Mg-6wt.%Al alloy were more uniform and thicker than those on pure Mg. The microhardness and friction coefficient of the coatings increased progressively as the coating time increased. In addition, the coatings on the Mg-6wt.%Al alloy compared to pure Mg showed improved microhardness and a better friction coefficient.

Optimum Fabrication Conditions and Reheating Characteristic of Semi-Solid Al-Zn-Mg-(Sc) Alloy by Inclined Cooling Plate (경사냉각판을 이용한 Al-Zn-Mg-(Sc) 반응고 합금 제조의 최적화 및 재가열 특성)

  • Kim, Tae-Hun;Shim, Sung-Yong;Park, Hyung-Won;Lim, Su-Gun
    • Journal of Korea Foundry Society
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    • v.29 no.5
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    • pp.213-219
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    • 2009
  • Optimum conditions for production of semi-solid Al-Zn-Mg alloy billets was carried out by the Taguchi design method. And, Al-Zn-Mg alloy billets contained Sc (free, 0.1 and 0.3 mass %) were fabricated at optimum conditions. Evolution of microstructure in semi-solid state was investigated through various liquid fractions, holding times and holding temperatures. The Al-Zn-Mg alloy billets reheated at $615^{\circ}C$ during 30min are grain growth and it was fractured due to increasing liquid fraction before quenching. And, during reheating up to $600^{\circ}C$, grain growth of Al-Zn-Mg alloy billets contained Sc (0.1 and 0.3 mass %) was not occurred in comparison with those of Al-Zn-Mg alloy without Sc. It was thought that $Al_3Sc$ phases have a pinning effect in grain boundary and Sc content of 0.1 mass% is able to inhibit grain growth effectively through reheating process.

Effects of Alloying Element and Heat-Treatment Condition on the Strength of Squeeze-Casted Al-3.0 wt%Si Alloy (용탕 단조 Al-3.0 wt%Si 합금의 강도에 미치는 합금 원소 및 열처리 조건의 영향)

  • Lee, Hag-Ju;Hwang, Jae-Hyoung;Kwon, Hae-Wook
    • Journal of Korea Foundry Society
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    • v.26 no.6
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    • pp.249-257
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    • 2006
  • The effects of alloying element and the condition of heat-treatment on the strength of squeeze-cast Al-3.0 wt%Si alloy were investigated. The strength of the alloy without grain refinement was increased with increase Cu content upto 3.0 wt% and rather decreased beyond that. The tensile strength of the alloy with grain refinement increased with Cu content upto 3.0 wt% and not changed beyond that. The strength of the alloy without grain refinement increased with the Mg content. The tensile strength with grain refinement increased with the Mg content upto 0.50 wt% and then decreased beyond that. The strength of the grain refined alloy increased by individual and simultaneous additions of Cu and Mg and the maximum strength was obtained with Al-3.0 wt%Si-4.5 wt%Cu-0.50 wt%Mg alloy. The optimum heat-treatment condition for this alloy was obtained.

Thermal Stability of Al-Fe-X Alloy System Prepared by Mechanical Alloying and Spark Plasma Sintering: I. Al-Fe (기계적 합금화 및 스파크 플라즈마 소결에 의해 제조된 Al-Fe-X계 합금의 열적 안정성: I. Al-Fe)

  • Lee, Hyun-Kwuon;Lee, Sang-Woo;Cho, Kyeong-Sik
    • Journal of Korean Powder Metallurgy Institute
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    • v.12 no.1
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    • pp.70-78
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    • 2005
  • Mechanical alloying using high-energy ball mill and subsequent spark plasma sintering (SPS) process was applied to understand mechanical alloying processing of Al-Fe alloy system. The thermal stability of mechanically alloyed Al-Fe alloy was intended to be enhanced by SPS process. Various analytical techniques including particle size analysis, density measurement, micro-Vickers hardness test, SEM, TEM, and X-ray diffractometry were adopted to find optimum processing conditions for mechanical alloying and subsequent SPS and to estimate thermal stability of the prepared alloy. It was found from the treatment of mechanically alloyed Al-8wt.%Fe powder mixture that needle-shaped $Al_3Fe$ precipitates was formed in the Al-Fe matrix, and the alloy compact showed enhanced densification and reached its full density with little loss of its fine microstructure. After heat treatment at $500^{\circC}$, it was also shown that the thermal stability of Al-8wt.%Fe alloy fabricated in the present study was enhanced, which was due to its fine microstructure developed by fast densification of SPS.

A Study on the fracture behavior of surface hardening treated aluminum alloy under the high velocity impact (고속충격을 받는 표면처리된 알루미늄 합금의 거동에 관한 연구)

  • 손세원;김희재;황도연;홍성희
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.784-789
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    • 2001
  • In order to investigate the fracture behaviors(penetration modes) and the resistance to penetration during ballistic impact of cold-rolled Al 5052 H34 alloy laminates, anodized Al 5052 H34 alloy laminates, and Al 5052 H34 alloy after cold-rolling, ballistic testing was conducted. In general, superior armor material is brittle materials which have a high hardness. Ballistic resistance of these materials was measured by protection ballistic limit(V50), a statical velocity with 50% probability for incomplete penetration. Fracture behaviors and ballistic tolerance, described by penetration modes, are observed respectfully, resulting from V50 test and Projectile Through Plate(PTP) test at velocities greater than V50. PTP tests were conducted with 0$^{\circ}$obliquity at room temperature using 5.56mm ball projectile. V50 tests with 0$^{\circ}$obliquity at room temperature were also conducted with projectiles that were able to achieve near or complete penetration during PTP tests. Surface Hardness, resistance to penetration, and penetration modes of Al 5052 H34 alloy laminates compared to those of cold-rolled Al 5052 H34 alloy laminates and anodized Al 5052 H34 alloy laminates anodized Al 5052 H34 alloy after cold-rolling.

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Effect of the Alloying Elements in Ag-Cu-Zr-X Brazing Alloy on the Microstructure and the Bond Strength of $Al_2O_3$/Ni-Cr Steel Brazed Joint (알루미나/니켈크롬강 접합체의 미세조직 및 접합강도에 미치는 Ag-Cu-Zr-X 브레이징 합금성분의 영향)

  • Kim, Jong-Heon;Yoo, Yeon-Chul
    • Transactions of Materials Processing
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    • v.7 no.5
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    • pp.465-473
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    • 1998
  • The effect of alloying elements of Ag-Cu-Zr-X brazing alloy on the microstructure and the bond strength of $Al_2O_3/Ni-Cr$ brazed steel joint was investigated. The reaction layer, $ZrO_2$ (a=5.146 ${\AA}$ , b=5.213 ${\AA}$ , c=5.311 ${\AA}$ )was formed at the interface of $Al_2O_3/Ni-Cr$ steel joint by the redox reaction between alumina and Zr. The addition of An and Al to the Ag-Cu-Zr brazing alloy gave rise to changes in the thickness of the reaction product layer and the morphology of the brazement. Sn caused the segregation of Zr was decreased b Al the $ZrO_2$ layer formed at the Ag-Cu-Zr-Al alloy was thinner than that of $ZrO_2$ formed at the Ag-Cu-Zr-An alloy. The fracture shear strength was strongly dependent on the microstructure of the brazement. Brazing with Ag-Cu-Zr-Sn alloy resulted in a better bond strength than with Ag-Cu-Zr or Ag-Cu-Zr-Al alloy.

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Effects of Mg and Si on Microstructure and Mechanical Properties of Al-Mg Die Casting Alloy (Al-Mg 계 다이캐스팅 합금의 미세조직 및 기계적 성질에 미치는 Mg 및 Si의 영향)

  • Cho, Jae-Ik;Kim, Cheol-Woo
    • Journal of Korea Foundry Society
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    • v.32 no.5
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    • pp.219-224
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    • 2012
  • The effects of Mg and Si contents on the microstructure and mechanical properties in Al-Mg alloy (ALDC6) were investigated. The results showed that phase fraction and size of $Mg_2Si$ and $Al_{15}(Fe,Mn)_3Si_2$ phase in the microstructure of Al-Mg alloy were increased as the Mg and Si contents were raised from 2.5 to 3.5 wt%. With Si content of 1.5 wt%, freezing range of the alloy was significantly reduced and solidification became more complex during the final stage of solidification. While there was no significant influence of Mg contents on mechanical properties, Si contents up to 1.5 wt%, strongly affected the mechanical properties. Especially elongation was reduced by about a half with more than 1.0 wt%Si in the alloy. The bending and impact strength were decreased with increased amount of Si in the alloy, as well. The lowered mechanical properties are because of the growth of particle shaped coarse $Mg_2Si$ phase and precipitation of the needle like $\beta$-AlFeSi in the microstructure at the last region to solidify due to presence of excess amount of Si in the alloy.

RRA Treatment of Semi-Solid Al-Zn-Mg-Cu Al Alloy Fabricated by Cooling Plate (냉각판으로 제조된 Al-Zn-Mg-Cu계 반응고 알루미늄 합금의 RRA 처리)

  • Kim, Dae-Hwan;Shim, Sung-Yong;Kim, Young-Hwa;Lim, Su-Gun
    • Journal of Korea Foundry Society
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    • v.29 no.6
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    • pp.265-269
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    • 2009
  • The optimum RRA heat treating conditions and SCC (stress corrosion cracking) resistance of semi-solid Al-Zn-Mg-Cu alloy fabricated by inclined cooling plate were compared with those of conventional mould cast alloys. The non-stirring method characterized by using a cooling plate can effectively eliminate dendritic structure and form a fine globular semisolid microstructure in as-cast Al-Zn-Mg-Cu alloy and the SCC resistance of semi-solid Al-Zn-Mg-Cu alloy was higher than that of conventional mold cast alloy. Also, after retrogressed treatment at RRA heat treatment of semi-solid Al-Zn-Mg-Cu alloy, retrogressed treatment time has increased more than 10 minutes at $180^{\circ}C$ to recovery the T6 heat treatment strength.

Influences of Precipitation of Secondary Phase by Heat Treatment on Thermal Properties of Al-4.5%Cu Alloy (열처리에 따른 제2상 석출이 Al-4.5%Cu 합금의 열 물성에 미치는 영향)

  • Choi, Se-Weon
    • Korean Journal of Materials Research
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    • v.30 no.8
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    • pp.435-440
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    • 2020
  • The relationship between the precipitation of secondary phase and the thermal properties of Al-4.5%Cu alloy (in wt.%) after various heat treatments has been studied. Solid solution treatment of alloy was performed at 808 K for 6 hours, followed by warm water quenching; then, the samples were aged in air at 473 K for different times. The thermal diffusivity of the Al-4.5%Cu alloy changed with the heat treatment conditions of the alloy at temperatures below 523 K. The as-quenched specimen had the lowest thermal diffusivity, and as the artificial aging time increased, the thermal diffusivity of the specimen increased in the temperature range between 298 and 523 K. For the specimen aged for five hours, the thermal conductivity was 12% higher than that of the as-quenched specimens at 298 K. It is confirmed that the thermal diffusivity and thermal conductivity of the Al-4.5%Cu alloy significantly depend on their thermal history at temperatures below 523 K. The precipitation and dissolution of the Al2Cu phase were confirmed via DSC for the alloys, and the formation of coefficient of thermal expansion peaks in TMA was caused by precipitation. The precipitation of supersaturated solid solution of Al-4.5%Cu alloys had an additional linear expansion of ≈ 0.05 % at 643 K during thermal expansion measurement.

A Study on the Die Casting of Mg-9Al-1Zn Alloy for Air Bag Case (Mg-9Al-lZn 합금 자동차 에어백 케이스의 다이캐스팅에 관한 연구)

  • Kim, Sun-Ho
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.10
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    • pp.77-83
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    • 2002
  • Magnesium alloys casting are gaining increased acceptance in the automotive and electronic industeries and die casting is the most efficient method of manufacturing such mass produced parts. This study has been investigated the microstructures and mechanical properties of Mg-9Al-lZn alloy fabricated by die casting process for development of air bag case. The microstructure of die casted specimen were composed of pro-eutectic magnesium solid solution and $\beta$(Mg17Al12) precipitates. The tensile strength of as-fabricated Mg-9Al-lZn alloy revealed 231.4MPa. It was found that Mg-9Al-lZn alloy have good corrosion resistance in electrochemical polarization test.