• Title/Summary/Keyword: grain refinement

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The Shear Texture Development and The Grain Refinement in Aluminum Alloy Sheets by Asymmetric Rolling (비대칭압연에 의한 알루미늄합금판의 전단집합조직 형성 및 결정립 미세화)

  • 이종국;이동녕
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.92-95
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    • 2003
  • Asymmetric rolling of AA1050 Al alloy sheets was performed to obtain the shear textures for improving the deep drawability and the grain refinement. The effect of roll velocity ratio on the texture and the grain refinement of 50% asymmetrically rolled sheets was studied. The textures of the asymmetrically rolled sheets after annealing at 400$^{\circ}C$ for 1 h was also investigated.

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The Effect of Grain Refinement by Ti Addition on Brazing Characteristic of 4343/3003/4343 Aluminum Clad Sheet (Ti 첨가에 의한 심재의 결정립미세화 처리가 4343/3003/4343 알루미늄 클래드 판재의 브레이징 특성에 미치는 영향)

  • Shin, Je-Sik;Moon, Byung-Moon
    • Journal of Korea Foundry Society
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    • v.30 no.5
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    • pp.187-195
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    • 2010
  • In this study, in order to obtain a useful guide line for design and production of automotive heat exchanger components made of 4343/3003/4343 aluminum clad sheets, it was aimed to improve the understanding about the grain refinement effect on brazing characteristic of the clad sheets. Al-10Ti master alloy was used for grain refinement of 3003 core alloy, and the Ti inoculation level was systematically changed up to 0.1 wt%. The three-layer aluminum clad sheets were fabricated by hot roll bonding process. The effect of grain refinement on brazing characteristic of the clad sheets was investigated by evaluating wettability, bonding strength and sagging resistance.

The Effect of Grain Refinement on Fluidity of Al-4.8%CU-0.6%Mn Alloy (입자미세화가 Al-4.8%Cu-0.6%Mn 합금의 유동도에 미치는 영향)

  • Kwon, Young-Dong;Lee, Zin-Hyoung;Kim, Kyoung-Hyun
    • Journal of Korea Foundry Society
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    • v.22 no.3
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    • pp.109-113
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    • 2002
  • A good fluidity of high strength Al-alloys is required to cast thin wall castings needed to reduce the weight of cast parts. The fluidity, measured as the length to which the metal flows in a standard channel, is affected by many factors, such as the pouring temperature, solidification type of the alloy, the channel thickness, melt head, mold materials and temperature, coating etc. Therefore the experimentally measured fluidity scatters very much and makes it difficult to estimate the fluidity of a melt with a few measurements. The effect of Ti content and grain refinement on the fluidity of high strength aluminum alloy was investigated with a test casting with 8 thin flow channels to reduce the scattering of the fluidity results. The fluidity of Al-4.8%Cu-0.6%Mn Al-6.2%Zn-1.6%Mg-1.0%Cu and well-known commercial aluminum alloy, A356 was tested. Initial content of Ti was varied from 0 to 0.2wt% and Al-5Ti-B master alloy was added for grain refinement. The flow length varied linearly with superheat. By adding Ti and Al-5Ti-B, the fluidity increased. The grain size decreased by adding grain refiner at the same time. The fluidity depended on the degree of grain refinement. The fluidity of the alloy solidifying in mushy type is improved by grain refinement, because grain refinement increases the solid fraction at the time of flow stoppage.

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.

Asymmetric Rolling as Means of Texture and Ridging Control and Grain Refinement (집합조직과 이랑형표면결함의 제어 및 결정립 미세화 수단으로서의 비대칭압연)

  • Lee D.N.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.11-18
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    • 2004
  • Asymmetric rolling, in which the circumferential velocities of the upper and lower rolls are different, can give rise to intense plastic shear strains and in turn shear deformation textures through the sheet thickness. The ideal shear deformation texture of fcc metals can be approximated by the <111> // ND and $\{001\}<110>$ orientations, among which the former improves the deep drawability. The ideal shear deformation texture for bcc metals can be approximated by the Goss $\{110\}<001>\;and\;\{112\}<111>$ orientations, among which the former improves the magnetic permeability along the <100> directions and is the prime orientation in grain oriented silicon steels. The intense shear strains can result in the grain refinement and hence improve mechanical properties. Steel sheets, especially ferritic stainless steel sheets, and aluminum alloy sheets may exhibit an undesirable surface roughening known as ridging or roping, when elongated along RD and TD, respectively. The ridging or roping is caused by differently oriented colonies, which are resulted from the <100> oriented columnar structure in ingots or billets, especially for ferritic stainless steels, that is not easily destroyed by the conventional rolling. The breakdown of columnar structure and the grain refinement can be achieved by asymmetric rolling, resulting in a decrease in the ridging problem.

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Effect of Ti, B, Zr Elements on Grain Refinement and Castability of Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe Casting Alloy (주조용 Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe 합금의 결정립 미세화와 주조특성에 미치는 Ti, B, Zr 첨가원소의 영향)

  • Kim, Heon-Joo;Park, Su-Min
    • Journal of Korea Foundry Society
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    • v.35 no.5
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    • pp.120-127
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    • 2015
  • The effects of Ti, B and Zr on grain refinement and castability were investigated in Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurement of cooling curve and micro-structure observation were performed to analyze the effects of the addition of minor elements Ti, B and Zr during solidification. The prominence of effect on grain refinement was in increasing order for Ti, Zr and B element. Fine grain size and an increase of the crystallization temperature for ${\alpha}$-Al solution were evident as the amount of addition elements increased in this study. Addition of 0.15wt% Ti was most effective for grain refinement, and the resulting grain size of ${\alpha}$-Al solution for shell mold and steel mold were $72.3{\mu}m$ and $23.5{\mu}m$, respectively. Fluidity and shrinkage tests were perform to evaluate the castability of the alloy. Maximum fluidity length and minimum ratio of micro shrinkage were recorded for 0.15wt% Ti addition due to the effect of the finest grain size.

Effect of Niobium on Corrosion Fatigue Properties of High Strength Steel

  • Cho, Young-Joo;Cho, Sang-Won;Kim, Jung-Gu
    • Corrosion Science and Technology
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    • v.17 no.2
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    • pp.81-89
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    • 2018
  • In this study, the effect of Nb alloying element on the corrosion fatigue properties of high strength steel is investigated by conducting fatigue experiments under corrosive condition and hydrogen induced condition, potentiodynamic polarization test, tensile test and surface analyses. Nb element is added to enhance the mechanical property of medium carbon steel. This element forms MX-type phases such as carbides and nitrides which are playing an important role in the grain refinement. The grain refinement is one of the effective way to improve mechanical property because both tensile strength and toughness can be improved at the same time. However, MX-type phase precipitates can be a susceptible site to localized corrosion in corrosive environment due to the potential difference between matrix and precipitate. The obtained results showed that Nb-added steel improved corrosion fatigue property by grain refinement. However, it is degraded for hydrogen-induced fatigue property due to Nb, Ti-inclusions acting as a stronger trap.

Shear Texture Development and Grain Refinement in Asymmetrically Rolled Aluminum Alloy Sheets : Effects of Shear Combinations (비대칭압연한 알루미늄합금판재의 전단집합조직발달과 결정립미세화 : 전단변형 조합의 영향)

  • 이종국;이동녕
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.132-135
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    • 2003
  • Asymmetric rolling, in which the ratio of the rotation rates of the upper and lower rolls was 2, has been used to introduce an intense plastic shear strain for the purpose of grain refinement and developing shear deformation textures through the sheet thickness to improve the strength and plastic strain ratio of AA1050 aluminum alloy sheets. The alloy sheets were rolled at room temperature without lubrication. The textures and microstructures of the sheets were investigated by x-ray diffraction and electron back-scattered diffraction (EBSD) analyses with emphasis on effects of combinations of rot ling directions.

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Stress Concentration Analysis of Grain Refinement in Rheology Casting Process

  • Z., Yang;P. K., Seo;J.H., Ko;Y. S., Jung;C. G., Kang
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.668-671
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    • 2004
  • The mechanics of the dendrite fragmentation is a very important aspect of grain refinement in rheocasting. In this work, the stress field of the dendrite stirred in the semisolid slurry was simulated by Metlab 6.0 software. The result shows that stress concentration at the root of the dendrite arms is great enough to cause plastic deformation though the agitation is moderate. Accordingly, dendrite fragmentation was suggested to be caused by fractured after fatigue erosion.

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The Effects of AlTi5B1 Additions on the Grain Refinement of Aluminium (알루미늄의 결정입자 미세화에 미치는 AlTi5B1 첨가의 영향)

  • Kim, Chung-Kun
    • Journal of Korea Foundry Society
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    • v.9 no.4
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    • pp.320-326
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    • 1989
  • Titanium-Boron-Aluminium master alloys are used extensively to grain-refine a wide range of aluminium alloys. This experiment was performed by various amounts of AlTi5B1 addition to the technical aluminium alloys, and also by changing cast temperature and hold time of the melts. The macrostructures were shown that with increasing the addition of AlTi5B1 to the melts, the grain became finer. In the case of cast temperature high enough over $900^{\circ}C$, the grain became coarser, but hold time change not affected on the grain refinement. Particles of $TiAl_3$, and $TiB_2$ were found in the grains and grainboundaries. The important role of grain refinement in this experiment were mainly $TiAl_3$, and also $TiB_2$ those have been confirmed in TEM, SEM, EDS, WDX and X-ray diffraction.

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