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7075 Al합금의 RRA처리에서 저온 퇴화처리의 효과
김창주,이정무,Kim, Chang-Joo,Lee, Jung-Moo 한국재료학회 1994 한국재료학회지 Vol.4 No.1
가공열처리한 7075Al합금을 $170^{\circ}C$에서 퇴화처리하여도 GP대는 완전히 분해되지 않았으며 초기의경도저하는 부분적인 GP대의 분해에 기인하고 $\mu '$의 생성으로 강도는 증가하다가 $\mu '$의 성장 및 $\mu$의 생성으로 강도는 다시 저하한다. 퇴화처리시 경도 곡선의 극소점이나 2차 피크점(극대점)에서 RRA처리한 시편의 응력부식 특성은 T6재에 비하여 상당히 개선되며 강도의 저하를 수반하지 않는다. 또한 저온인 $170^{\circ}C$에서 퇴화처리시 기지조직의 변화가 크지 않아 퇴화처리시 경도곡도의 극소점과 2차 피크점에서의 특성차이는 거의 없었다. Effect of low temperature retrogression on RRA treatment were investigated in the thermomechanically treated 7075 Al alloy. The complete dissolution of GP zones did not occur during retrogression at $170^{\circ}C$ in T6 material. llrop in strength during initial stage of retrogression was due to the partial dissolution of GP zones. And the strength increased with the formation of $\mu '$ and decreased again with the growth of $\mu '$ and/or formation of $\mu '$ When RRA treatment was applied at the minimum or the secondary peak (maximum) in the hardness curve of retrogression treatment, SCC property was improved markedly without reduction of the strength in comparision with that of T6 materials. And the rhanges in the matrix were not sensitive with time during retrogression at low temperature of $170^{\circ}C$ that the strength and SCC properties were similar at both points in the hardness curve of retrogression treatment.
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%.
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.
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.
Cu-6Ni-3Mn-6Sn 합금의 미세조직변화에 미치는 첨가원소의 영향
김창주,박영구,한승전,서승필,이정무 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.6
The physical and mechanical properties of the Cu-6%Ni-3%Mn-6%Sn-0.5%X(Al,Ti,Si)alloys and Cu-6Ni-3Mn-6Sn alloy were strongly dependent on aging condition. The effects of additions of Al, Si and Ti on the mechanical properties and formation of discontinuous precipitate in the alloy have been investigated. In this alloy discontinuous precipitation occurs during aging at 350℃ for 405 min. But addition of Si and Ti in this alloy, discontinuous precipitation occurs much less than the Cu-6Ni-3Mn-6Sn alloy and grain size is decreased. For Cu-6Ni-3Mn-6Sn-X alloy system, spinodal decomposition and transition of metastable phase does not occur but discontinuous precipitation decreased with addition of 0.5% Si, Ti and Al respectively. Also grain size is reduced by addition of 0.5% Si and Ti on Cu-6Ni-3Mn-6Sn alloy because of forming interphase in grain boundary.
Cu-(9-X)Ni-XMn-6Sn 합금의 미세조직과 경도에 미치는 시효의 영향
김창주,박영구,한승전,서승필,이정무 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.12
Decomposition precess of α phage in Cu-(9-X)Ni-XMn-6Sn alloy has been investigated by means of side band observation around (200)_α X-ray diffraction peak, hardness, and microstructural observations. When the specimens are aged below 400℃ after solution treatment, the supersaturated solid solution α' is decomposed by three stages. When the specimens are aged above about 500℃, however, the equilibrium cellular structure consisting of α phase and DO_3 type superlattice forms from the initial stage of transformation without any reactions such as spinodal decomposition and transition of metastable phase. In Cu-8Ni-1Mn-6Sn and Cu-7Ni-2Mn-6Sn alloys, the first stage and the second stage in the decomposition of supersaturated solid solution are occurred at the same time. And all stages are occurred earlier than Cu-9Ni-6Sn alloy.
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.
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-6Ni-4Sn 합금에 있어서 α 과포화 고용체의 분해거동에 미치는 Mm(Ce, La, etc) 의 미량첨가 효과
김창주,이정무,한승전,정윤철,변상섭 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.6
The Effect of very small addition of misch metals (La, Ce, etc) on the decomposition behavior of the supersaturated solid solution a in Cu-6%Ni-4%Sn(wt.%) alloy was investigated by means of microstructural observations such as optical, scanning and transmission electron microscopies. In the case of Cu-6Ni-4Sn alloy which does not contain Mm, the supersaturated solid solution α was not decomposed into other phases such as spinodal decomposition, γ′ (D0_(22) and y (D0₃) by aging after solution treatment. The small addition of Mm to the Cu-6%Ni-4%Sn alloy, on the other hand, affected markedly the decomposition behaviors of the supersaturated solid solution α. In addition, the grain growth was significantly retarded by the small addition of Mm. In this alloy containing Mm, the supersaturated solid solution α was decomposed into γ′ and γ phases with aging time, indicating that the supersaturated solid solution α was decomposed by the spinodal decomposition in the first stage.