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RISS 인기검색어
- 검색키워드
- 저자 : Abbaschian Reza (검색결과 5 건)
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김동익,Abbaschian, Reza 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.9
The effect of cooling rate on the metastable liquid phase separation(MLPS) in Cu-Fe binary and Cu-Fe-Co ternary alloys was investigated using an electromagnetic levitation technique. The cooling rate during phase separation was controlled by dropping the specimens to copper substrate which was in 15 ㎝ apart from levitation coil. The cooling rate in levitation state was 5-20 K/sec, and those of free falling and after splash were 130 K/sec and 2300 K/sec respectively. In the specimen solidified at medium cooling rate(about 130 K/sec), secondary phase separation was observed in both L1(Fe- or Fe, Co-rich phase) and L2(Cu-rich phase) phases that have been formed by primary phase separation. In this case the phase separation occured by nucleation and growth. Spinodal decomposition is considered as a dominent phase separation mechanism in L1 droplets solidified at fast cooling rate (about 2300 K/sec). There was no evidence of spinodal decomposition in L2 phase.
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김동익,Abbaschian, Reza 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.12
Metastable liquid phase separation(MLPS) in Cu-Fe binary system was investigated using an electromagnetic levitation technique. The temperature of the MLPS(Tsep) was measured directly from the time-temperature profile during cooling in the levitated state. The metastable liquid miscibility boundary of Cu-Fe binary system was illustrated using these measured Tsep. In Fe-rich alloys, phase separation generally appeared as dispersed L2(Cu-rich) droplets in a L1(Fe-rich) matrix, whereas for alloys containing Fe less than 53 wt%, L1 droplets formed in a L2 matrix. Secondary MLPS was occured in the primary separated L1 droplets by increasing the cooling rate during phase separation.
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Cu-Co 2 원계 합금에서 준안정 액상의 상분리와 미세조직
김동익,Abbaschian, Reza 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.1
Metastable liquid phase separation(MLPS) in Cu-Co binary system was investigated using an electromagnetic levitation technique. In Co-rich alloys, Phase separation generally appeared as dispersed L2(Cu-rich) droplets in a L1(Co-rich) matrix, whereas for alloys containing Co less than 55 wt%, L1 droplets formed in a L2 matrix. Secondary MLPS was occurred in the primary separated L1 droplets by increasing the cooling rate during phase separation. The effect of undercooling and cooling rate on the microstructure of L1 phase was investigated. The microstructure of L1 phase was found to fall into three categories of dendrite, spherical and mixed (dendritic plus spherical) morphology. As the undercooling and/or cooling rate was increased the spherical morphology became a dominent structure.
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Cu-Co-Fe 3 원계 합금의 준안정 액상 상분리 및 응고조직
김동익,Abbaschian, Reza 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.2
Metastable liquid phase separation(MLPS) in Cu-Co-Fe ternary system was investigated using an electromagnetic levitation technique. The temperature of the metastable liquid phase separation(Tsep) was measured directly from the time-temperature profile during the cooling in levitated state. The metastable liquid miscibility boundary of the Cu-Co-Fe ternary was determined using the measured Tsep and the compositional analysis of the separated phases. Metastable liquid phase separated structures of Cu-Co-Fe system were found to be consistent with (Co, Fe)-Cu quasi binary phase diagram. In Cu-rich alloys, phase separation generally appeared as dispersed L1(Co, Fe rich phase) droplets in a L2(Cu rich phase) matrix, whereas for alloys containing Cu less than 45-47 wt%(depending on the alloy composition), L2 droplets formed in a L1 matrix. Secondary metastable liquid phase separation were observed in specimens which were cooled rapidly against a copper substrate.
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On the control of structural/compositional ratio of coherent order-disorder interfaces
Forghani, Farsad,Han, Jong Chan,Moon, Jongun,Abbaschian, Reza,Park, Chan Gyung,Kim, Hyoung Seop,Nili-Ahmadabadi, Mahmoud Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.777 No.-
<P><B>Abstract</B></P> <P>Order-disorder coherent interfaces determine the microstructure and mechanical properties of precipitation-hardened high-temperature alloys. The characteristics of these interfaces can be defined by a compositional width, δ, and structural width, δ′. The latter, which can be considered as the width of the ordered part of the interface, can play an important role in high-temperature mechanical behavior of precipitation-hardened alloys. This is due to the fact that diffusion in the ordered part of the interface is generally much slower than diffusion in the disordered phase, thus hindering the solid-state diffusion-based phenomena. Here, we investigate the order-disorder interface in a Ni-19Al (at.%) alloy as a model alloy for Ni-based superalloys using atomic-resolution scanning transmission electron microscopy and three-dimensional atom probe tomography. Then, we employ thermodynamic modeling to describe the interplay between the structural and compositional interface widths in binary Ni-Al and in ternary Ni-Al-Cr and Co-Al-W systems. We introduce the δ′/δ ratio as a critical parameter that varies significantly in different alloys. Our findings offer a general pathway to control the δ′/δ ratio of interfaces, which in turn affect the high-temperature properties of precipitation-hardened alloys.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Characterization of the order-disorder coherent interface in a Ni-19Al model alloy. </LI> <LI> Describing the dual nature of order-disorder coherent interfaces. </LI> <LI> Prediction of the structural interface width δ′ based on the thermodynamic modeling. </LI> <LI> Introducing the δ′/δ ratio as a critical parameter that varies in different alloys. </LI> </UL> </P>
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