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Directional Solidification Processing on CET in Al-Based Alloys
정혜진,N. Mangelinck-Noël,H. Nguyen-Thi,B. Billia,G. Reinhart,A. Buffet 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.1
The control of the transition from columnar to equiaxed (CET) dendrite microstructure is an important point to obtain desired final properties of industrial products. The objective is to understand how the formation and the evolution of the CET are influenced by the processing parameters and natural convection with Al - 3.5 wt.% Ni and Al - 7.0 wt.% Si alloys. Various experiments are carried out in a Bridgman furnace for which the thermal gradient and pulling velocity can be independently controlled. We concentrate our interest on the CET tendency, added particle effects and the evolution of dendrite grain structures under different test conditions. On the other hand, in-situ and real time observation of the solid-liquid interface is used to reveal the dynamics of the phenomena that occur, thus deepening our understanding. To achieve this objective, Synchrotron X-ray Radiography has been designed and performed at the European Synchrotron Radiation Facility. The control of the transition from columnar to equiaxed (CET) dendrite microstructure is an important point to obtain desired final properties of industrial products. The objective is to understand how the formation and the evolution of the CET are influenced by the processing parameters and natural convection with Al - 3.5 wt.% Ni and Al - 7.0 wt.% Si alloys. Various experiments are carried out in a Bridgman furnace for which the thermal gradient and pulling velocity can be independently controlled. We concentrate our interest on the CET tendency, added particle effects and the evolution of dendrite grain structures under different test conditions. On the other hand, in-situ and real time observation of the solid-liquid interface is used to reveal the dynamics of the phenomena that occur, thus deepening our understanding. To achieve this objective, Synchrotron X-ray Radiography has been designed and performed at the European Synchrotron Radiation Facility.
Variation of microstructure by Ru additions in a single crystal Ni based superalloy
Tan, X.P.,Liu, J.L.,Jin, T.,Hu, Z.Q.,Hong, H.U.,Choi, B.G.,Kim, I.S.,Jo, C.Y.,Mangelinck, D. Maney Publishing 2014 Materials Science and Technology Vol.30 No.3
The microstructural variation of three single crystal Ni based superalloys with various Ru contents has been investigated. The as cast, solid solution and fully heat treated microstructures were quantitatively analysed. The size of gamma' phase was decreased both in dendrite core and interdendritic regions with Ru additions after a solid solution heat treatment. Appropriate heat treatment schemes of three alloys were determined in terms of quantitative and qualitative microstructural characterisation. It was found that the size and volume fraction of gamma' phase were decreased, and the width of c matrix channels was reduced in the dendrite core regions of fully heat treated microstructure with the additions of Ru. Moreover, the well known reverse partitioning occurred with increasing Ru content. The gamma/gamma' lattice misfits changed from positive to negative and became more negative with Ru additions. The variation of gamma/gamma' lattice misfit was caused by the changes of partitioning ratios of alloying elements via Ru additions.
Tan, X.P.,Liu, J.L.,Jin, T.,Hu, Z.Q.,Hong, H.U.,Choi, B.G.,Kim, I.S.,Jo, C.Y.,Mangelinck, D. Elsevier Sequoia 2013 Materials science & engineering. properties, micro Vol.580 No.-
The creep deformation of three single crystal Ni-based superalloys with various Ru contents has been investigated to clarify the effect of Ru additions at very high temperatures and low stresses conditions. The creep properties were significantly improved by Ru additions under the conditions of 1150<SUP>o</SUP>C/100MPa and 1180<SUP>o</SUP>C/70MPa. It is noted that obvious γ' phase dissolution occurs during the entire creep deformation at very high temperatures. It differs from the typical high-temperature creep curves that a short incubation period occurs before the primary creep stage during the creep deformation at very high temperatures. Ru additions are able to produce denser interfacial dislocation networks and improve the stability and homogeneous configuration of interfacial dislocations; and promote the high-temperature stability of γ' phase and formation of perfect γ' rafting. It is thus shown that Ru additions reduce the minimum creep rate, and prolong the secondary creep stage accordingly. The topological inversion of γ/γ' microstructure did not occur under both conditions. The origin of the rapid increase of creep rate is closely relevant to the unstable propagation of micro-cracks in the vicinity of porosity in necked regions.