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논문 : 기계적 성질 ; Cu-9Ni-6Sn 합금의 기계적 성질에 미치는 Al, Ti, Si, Sb의 첨가효과
정윤철 ( Yun Chul Jung ),한승전 ( Seung Zeon Han ),이정무 ( Jung Moo Lee ),김창주 ( Chang Joo Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.6
The effects of additions of Al, Ti, Si and Sb on the mechanical properties, electrical resistivity and formation of discontinuous precipitate in Cu-9Ni-6Sn(wt%) alloy have been investigated. The physical and mechanical properties of the Cu-9Ni-6Sn alloy were strongly dependent on aging conditions. This alloy was much strengthened by aging at temperatures below 350℃ where the spinodal decomposition occurs, but the specimen does not be strengthened by aging at temperatures above 400℃ where the discontinuous precipitate forms. Al suppressed the formation of discontinuous precipitation and increased the electrical resistivity. The nucleation of discontinuous precipitate was significantly retarded by the small additions of Ti and Si and the discontinuous product has never formed up to 5h even at 450℃. The addition of Sb. on the other hand, was not affected markedly. In all of the alloys examined, the electrical resistivity was decreased by aging and the degree of reduction increased with increasing aging temperature and aging time.
논문 : 기계적 성질 ; Cu-9Ni-xSn 합금의 기계적 성질에 미치는 Sn 함량 및 Sn의 역활
정윤철 ( Yun Chul Jung ),김창주 ( Chang Joo Kim ),한승전 ( Seung Zeon Han ),이정무 ( Jung Moo Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.7
The effects of Sn contents on the mechanical properties and the role of Sn in the Cu-9Ni-xSn alloys have been investigated and the following results have been obtained. The mechanical properties such as tensile strength, elongation and electrical resisitivity of Cu-9Ni-xSn alloys are strongly dependent on aging temperature, aging time and Sn contents. With increasing Sn contents, the tensile strength is increased and the temperature where the spinodal decomposition occurs and the incubation time to start spinodal decomposition are lowered and reduced, respectively. By aging treatment at temperatures below 350℃, the 5%<Sn alloys are much strengthen but the aging effect does not be observed in the 3%>Sn alloys. In the case of the 5%<Sn alloys, the electrical resisitivity is significantly reduced by aging treatment and the degree of reduction increases with increasing the Sn contents and aging temperature. These results obtained in this examination indicate that the strengthening mechanisms of the Cu-9Ni-xSn alloys can be changed by the Sn contents and aging temperature. Considering the results obtained in the present study and the equilibrium phase diagram of Cu-Ni-Sn, the minimum Sn contents to occur spinodal decomposition in the Cu-9Ni--xSn alloys are thought to be about 4wt%.
Cu-Ni-Sn 합금의 상변태거동 및 기계적 성질에 미치는 Mn 첨가효과
김창주,이정무,한승전,정윤철 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.8
The effects of Mn addition on phase transformation behavior and mechanical properties of Cu-(9-x)Ni-xMn-6Sn alloys were investigated. The microstructure and transformation behavior changed with increasing Mn content and heating temperature. The Mn free alloy decomposed spinodally by aging at 350℃ and followed by formation of a metastable γ′ phase which accompanies the increase of mechanical characteristics with increasing Mn content, however, the γ′ phase disappeared and a stable γ phase was dominantly precipitated. When the specimens were aged above 450℃, equilibrium γ phase formed from the initial stage of transformation without any reaction such as spinodal decomposition and transformation of a metastable phase. Therefore, addition of Mn and increasing heating temperature suppressed the hardening effect of alloy in the early stage of aging, and decreased the tensile strength.
Cu-6wt%Ni-4wt%Sn 합금의 기계적 전기적 성질에 미치는 Mm (Ce, La, etc) 의 미량 첨가 효과
김창주,이정무,한승전,정윤철,변상섭 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.10
The effect of small addition of Mm(Ce, La, etc) on the mechanical properties and electrical resistivity of Cu-6Ni-4Sn(wt%) alloy has been investigated by means of microstructural observation as well as the tensile and electrical resistivity tests. The Cu-6Ni-4Sn alloy was found not to strengthen by an aging treatment after cold working but the tensile strength of this alloy was decreased with increasing the aging temperature, indicating that the spinodal decomposition didn't occur in the α supersaturated solid solution. The grain growth was significantly suppressed by the small addition of Mm, resulting into the substantially enhanced mechanical properties. The tensile strength and elongation of the Cu-6Ni-4Sn-0.05Mm alloy was found to increase with increasing aging temperature at low temperature range possibly due to the spinodal decomposition and CeNi₄Sn₂ precipitation. The electrical resisitivity was significantly reduced by the small addition of Mm. In all of the alloys examined, the electrical resistivity was reduced by raising the aging temperature. The Mm addition is found to reduce the electrical resistivity more rapidly as the aging temperature increases.
연속 주조한 Cu-9Ni-6Sn 합금의 열처리에 따른 가공성 및 미세조직변화
김창주,이정무,한승전,정윤철,김홍일 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.7
The effects of Heat-treatment on the mechanical workability of continuously cast Cu-9Ni-6Sn alloys have been investigated and the following results were obtained. The mechanical workability of Cu-9Ni-6Sn alloys are strongly dependent on the temperature of heating. The surface cracks of specimen were not produced over the temperature of 650℃ but occurred below 650℃. Sn-rich inclusion formed during solidification influenced the mechanical workability. Especially Sn-rich inclusion at grain-boundary induced crack initiation. Over the holding temperature of 650℃, the grain boundary pore made by removing inclusion initiated crack because the pores acted as defect at the grain boundary. Below 650℃, Sn-rich inclusions were still remained at the grain boundary, therefore workability improved due to reduction of defects at the grain boundary.
Cu-6Ni-6Sn 합금에서 시효경화 거동에 미치는 Mn 첨가의 효과
김창주,이정무,정윤철,한승전 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.8
The effects of addition of Mn on age hardening behaviors of Cu-6wt.%Ni-6wt.%Sn were investigated. The microstructural and hardness changes of alloys aged at 350 to 550℃ were studied by optical microscopy and X-ray diffraction techniques. The Mn free alloy decomposed spinodally by aging at 350℃ followed by the formation of metastable γ' phase which accompanies the increase of hardness. Further aging transformed metastable γ' phase to cellular structure of α+γ. When the specimens were aged at 450℃ and above, cellular structure of α+γ formed without spinodal decomposition and transition of metastable phase. The additions of Mn affected the sequences of precipitation. Additions of Mn suppressed spinodal decomposition of the alloy in the early stage of aging and exhibited a incubation period in hardness change. Hardening was accompanied by the formation of MnNi₂Sn phase.
Ti-3Al-8V-6Cr-4Mo-4Zr (β-C) 합금의 기계적 성질과 피로한도에 미치는 용체화처리 온도와 미세조직의 영향
김창주,손성만,정윤철 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.3
Effects of solution treatment(ST) and aging temperatures on the behavior of β decomposition and the mechanical properties of β-C alloy have been investigated mainly by means of TEM observations. In the initial stage of transformation at temperatures below 480℃, a modulated(or tweed) structure forms on a {110}_β and aligns <111>_β. And then a metastable β′ nucleates along the modulated structure. At the later stage of transformation, the equilibrium a phase nucleates at the β/β′interface and grows preferentially to <111>_β with Burgers relationship to β matrix. The β grain size and the fatigue limit are strongly dependent on ST temperature. The elongation, the yield and tensile strengths, however, are approximately constant independently of the ST temperature. Aging at 480℃ after ST at 800℃ gives the highest tensile strength but shows the lowest ductility in the present study. This result is considered to occurred by the large amounts of β′ and extremely fine needlelike α precipitates, which induce much elastic strains in the β matrix. Aging at 530℃ after ST at 800℃ gives improved tensile strength and ductility combination and represents the fatigue strength as high as 605㎫ with the high endurance ratio of 0.536. The mechanical properties of the specimens solution treated at 800℃ followed by aging treatment are better than those of the specimens solution treated at 900℃ followed by aging treatment. Therefore, it is indispensable for obtaining a better combination of strength, ductility and fatigue limit in the β-C alloy to select an adequate ST and aging temperatures.