• 제목/요약/키워드: Columnar Dendrites

검색결과 3건 처리시간 0.02초

내열 금형강 DED 금속적층재의 조직, 결함 및 기계적 물성 평가 (Microstructure, Defects and Mechanical Properties of DED Metal Deposited Heat-Resistant Mold Steel)

  • 최성종;김호찬
    • 한국기계가공학회지
    • /
    • 제21권3호
    • /
    • pp.12-21
    • /
    • 2022
  • Directed energy deposition (DED) was adopted as a metal additive manufacturing method to develop a mold for the hot stamping process. The test piece was machined from Heatvar laminate material, and results were obtained through microstructure and defect observations, as well as hardness, tensile strength, and joint strength tests. 1) Spherical pores and irregular-shaped cavities were observed as lamination defects, and columnar dendrites formed in the structure, which tended to become coarse upon heat treatment. 2) The hardness of the heat-treated material (480HV) was slightly lower than that of the non-heat-treated material (500HV). 3) In the tensile test, the maximum tensile stress and strain of the heat-treated material were 1392 MPa and 15%, respectively, which were slightly higher than the values of 1381 MPa and 13%, respectively, for the non-heat-treated material. 4) In the case of the early final fracture in the tensile test, in most cases, pores or irregularly shaped cavities were observed at the fracture surface or near the surface. 5) In the joint strength test, most of the specimens finally fractured in the laminated metal area, and the fracture surface was intragranular. In addition, dimples formed over the entire area on the fracture surface of the fractured specimen after sufficient elongation.

Al-Si이원계 합금의 응고현상에 미치는 정수압의 영향(I);금속 조직적 연구 (Effects of Hydrostatic Pressure on Solidification Phenomena of Al-Si binary alloys(I);Metallurgical Study)

  • 한요섭;김도향;이호인
    • 한국주조공학회지
    • /
    • 제6권2호
    • /
    • pp.116-121
    • /
    • 1986
  • The effects of pressure during solidification on macro-and micro-structures have been studied in pure aluminium and Al-Si alloys. The application of pressure during solidifcation accelerated both equiaxed and columnar dendritic-growth due to stimulating of equiaxed survival and faster preferential growth of primary dendrites against the parallel direction of heat flow. Burden-Hunt model was modified to express the significant changes of CET behaviours under pressure. A further point to be noted was that greatly fine eutectic silicon flakes ($0.5\;{\times}\;13{\mu}m$) with the decrease of halo layers ($7{\mu}m$) of aluminium riched phases in the periphery of primary silicon particles were observed when pressure was applied during solidification.

  • PDF

전자기 듀오캐스팅으로 제조한 Al-Mn/Al-Si 하이브리드 알루미늄합금의 미세조직과 인장 특성 (Microstructure and Tensile Properties of Al-Mn/Al-Si Hybrid Aluminum Alloy Prepared by Electromagnetic Duo-Casting)

  • 박성진;;김종호;박준표;장시영
    • 한국재료학회지
    • /
    • 제22권2호
    • /
    • pp.97-102
    • /
    • 2012
  • The microstructure and tensile properties of Al-Mn/Al-Si hybrid aluminum alloys prepared by electromagnetic duocasting were investigated. Only the Al-Mn alloy showed the typical cast microstructure of columnar and equiaxed crystals. The primary dendrites and eutectic structure were clearly observed in the Al-Si alloy. There existed a macro-interface of Al-Mn/Al-Si alloys in the hybrid aluminum alloys. The macro-interface was well bonded, and the growth of primary dendrites in Al-Si alloy occurred from the macro-interface. The Al-Mn/Al-Si hybrid aluminum alloys with a well-bonded macro-interface showed excellent tensile strength and 0.2% proof stress, both of which are comparable to those values for binary Al-Mn alloy, indicating that the strength is preferentially dominated by the deformation of the Al-Mn alloy side. However, the degree of elongation was between that of binary Al-Mn and Al-Si alloys. The Al-Mn/Al-Si hybrid aluminum alloys were fractured on the Al-Mn alloy side. This was considered to have resulted from the limited deformation in the Al-Mn alloy side, which led to relatively low elongation compared to the binary Al-Mn alloy.