• Title, Summary, Keyword: Grain Refinement

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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.

Design of Rolling Path Schedule for Refinement of Austenite Grain (오스테나이트 결정립 미세화를 위한 후판 압연 패스 스케줄의 설계)

  • Hong, Chang-Pyo;Park, Jong-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.11
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    • pp.1844-1853
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    • 2001
  • In the present investigation, it was attempted to design the rolling pass schedule fur a clean steel of 0.1C-1.5Mn-0.25Si with the objective of the austenite grain refinement. As the method of approach, a coupled mathematical modeling technique was proposed which consists of a recrystallization model and a flow stress modes. The validity of the coupled model was examined through comparison with results of continuous and discontinuous compression tests at various temperatures, strains and strain rates. The coupled model was incorporated with the finite element method to set up a systematic design methodology far the rolling path schedule for austenite grain refinement. Two path schedules were obtained and discussed in the paper with regard to rolling path time, average grain size, grain size deviation in thickness, etc.

Grain Refinement and Mechanical Properties Improvement in a Severely Plastic Deformed Ni-30Cr Alloy (강소성 가공된 Ni-30Cr 합금의 결정립 미세화와 기계적 물성 향상)

  • Song, Kuk Hyun;Kim, Han Sol;Kim, Won Yong
    • Korean Journal of Metals and Materials
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    • v.49 no.8
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    • pp.649-656
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    • 2011
  • The present study evaluated the microstructures and mechanical properties of severely deformed Ni-30Cr alloys. Cross-roll rolling (CRR) process was introduced as a severe plastic deformation (SPD), and Ni-30Cr alloy sheets were cold rolled to 90% thickness reduction and subsequently annealed at $700^{\circ}C$ for 30 min to obtain the recrystallized microstructure. Electron back-scattering diffraction (EBSD) was introduced to analyze grain boundary character distributions (GBCDs). The application of CRR to the Ni-30Cr alloy was effective in enhancing the grain refinement through heat treatment; consequently, the average grain size was significantly refined from $33{\mu}m$ in the initial material to $0.6{\mu}m$. This grain refinement directly improved the mechanical properties, in which yield and tensile strengths significantly increased relative to those of the initial material. We systematically discuss the grain refinement and accompanying improvement of the mechanical properties, in terms of the effective strain imposed by CRR relative to conventional rolling (CR).

Grain Refinement of Mg-5wt%Zn Alloy by Rapid Solidification Process (급냉응고에 의한 Mg-5wt%Zn 합금의 결정립 미세화)

  • Kim, Yeon-Wook;Lee, Eun-Jong;Hur, Bo-Young
    • Journal of Korea Foundry Society
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    • v.17 no.3
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    • pp.302-308
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    • 1997
  • In spite of the fact that magnesium has low density and good machinability, its applications are restricted as a structural engineering material because of the poor strength, ductility, and corrosion resistance of the conventional ingot metallurgy alloys. Such properties can be improved by microstructural refinement via rapid solidification processing. In this study, Mg-5wt%Zn alloys have been produced as continuous strips by the melt overflow technique. In order to evaluate the influence of the cooling rate on the grain refinement and mechanical properties, seven different thickness strips were produced by means of controlling the speed of the cooling wheel. Then the microstructual observations were undertaken with the objective of evaluating the grain refinement as function of the cooling rate. The tremendous increase in hardness of Mg-Zn alloy was mainly due to the refinement of the grain structure by the effect of rapid solidification. The formation of intermetallic phases on the grain boundaries may have a positive effect on the corroion resistance. Therefore, despite competition from many other developments, the rapid solidification process emerges as a valuable method to develop superior and commercially acceptable magnesium alloys.

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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 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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Effect of Ti and Sr on the Microstructure of Al-Si-Mg Casting Alloy (Al-Si-Mg계 주조합금의 미세조직에 미치는 Ti 및 Sr첨가 영향)

  • Jeong, Jae-Yeong;Kim, Gyeong-Hyeon;Kim, Chang-Ju
    • 한국기계연구소 소보
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    • pp.71-78
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    • 1990
  • This investigation was undertaken to establish the technologies of grain refinement and modification, and to characterize material properties, essential for high quality aluminum alloy castings. Grain refinement seldom changed DAS and eutectic Si size, but largely decrease grain size. The variations of grain size induced by grain refinement had a great influence on the elongation without changes in the tensile strength or yield strength. The optimum Ti level lies between 0.1% and 0.16% to achieve the best possible mechanical properties. DAS and grain size were little affected, but eutectic Si size was greatly refined by modification. The variation of eutectic Si size had a great effect on the elongation, impact value, fracture toughness and fatigue crack propagation rate without changes in the tensile strength or yield strength. The Sr content of 0.015% is optimum to modification.

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Effects of Zr, B and P Additions the Grain Refinement of CuZn36 Alloys. (CuZn36 합금의 입자 미세화에 미치는 Zr, B, P 첨가의 영향)

  • Kim, Chung-Keun;Lee, Dong-Woo
    • Journal of Korea Foundry Society
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    • v.13 no.2
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    • pp.168-174
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    • 1993
  • It has been known that the grain refinement of Cu base alloys greatly improved mechanical properties, castability, workability and hot shortness resistance etc. In this study CuZr50, CuP7, CuFe7, CuMg10 binary alloys were added as grain refiners in CuZn36 alloy. The alloys melted in vacuum and controlled in mixed gas conditions and casted at $1050^{\circ}C$. Zr-P-X compound has significantly grain refined but oxygen has been found detrimental to grain refinement. In the case of Zr /B ratio below 4, B acted as grain growth element in this alloy.

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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.