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급냉응고법에 의한 Al-9Zn-2.5Mg-1Cu-X P/M재의 제조 및 성질
임수근 慶尙大學校生産技術硏究所 1990 生産技術硏究所論文集 Vol.6 No.-
Rapidly solidified flakes of 7090 based aluminum alloys containing transition metals were produced by atomizing the alloy melt and subsequent splat quenching onto a water-cooled copper single roll. Consolidation of these flakes was done by cold pressing, degassing and hot extrusion at a reduction ratio of 25 to 1. As splat-quenched flakes showed cellular structure, consisting of primary phase and eutectic. The hardness of flakes and P/M materials increased with the addition of transition metals due to fine dispersion of their eutectic compounds. Mn was most effective for strengthening 7090 based alloy by the addition of transition metals. Tensile strength of T6 materials with 6 wt% Mn addition was 817MPa, and that of 2 wt% Mn addition was 787 Mpa. Furthermore, Mn bearing materials showed appreciably higher specific strength and specific elastic modulus than Ti alloy in room temperature.
Composite Materials-: SiC 휘스커강화 2024 및 7075 알루미늄합금기 복합재료의 제조와 기계적 특성
임수근,김준수 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.2
Unidirectionally reinforced Al 2024 and Al 7075 composites with SiC whiskers were fabricated by high pressure infiltration technique and subsequent hot extrusion. The microstructure, age hardening behavior and mechanical properties of the composites were examined. Hot extrusion enabled the unidirectional alignment of whiskers, but substantial amount of whiskers was broken during extrusion. The whisker reinforcement tends to accelerate the age hardening, and decrease the amount of aging, due to the inhomogeneous precipitation of stable phases at the lattice defects in the matrix. The beneficial effect of whisker reinforcement was observed up to 473K. Above 573K, however, the mechanical properties of the composite were comparable to those of the unreinforced alloys, attributable to the enhanced grain boundary sliding due to the fine grain structure formed during hot extrusion.
임수근,김권섭 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.4
Semi-solid metal was obtained by semi-solid continuous casting apparatus which consisted of melting furnace, cooling plate and continuous casting part. Primary α size, aspect ratio and hardness of an A356 Al alloy have been investigated. Crystal seeds of the primary α were nucleated on a cooling plate. The seed of primary crystals existing in the molten alloy grew granular grain. The minimum size of primary α at pouring temperature 700℃ were 65 ㎛ in BN coated cooling plate, 53 ㎛ in BN uncoated cooling plate. BN coated cooling plate prevented molten metal from becoming hard. The primary α size increases from 53 ㎛ to 61 ㎛ as casting temperature increase from 630℃ to 650℃. The aspect ratio was increased with increasing primary α size. To investigate the effect of addition of Al-5Ti-1B master alloy is added to A356 Al alloy. The primary α size and aspect ratio are about 42 ㎛ and 1.3 at the content of additional 0.5% grain refiner. The solid fraction of the α phase are about 60∼70%.