Abstract
Influence of 2-6% Re additions has been investigated on the solidification phenomenon of a Ni base superalloy, In718. The solidification of each alloy proceeds in the order of primary γ, eutectic (γ+NbC) and eutectic (γ+Ni 2 Nb). Higher additions of Re increase the volume fraction of primary y and enlarge the secondary dendrite arm spacing. The influence of cooling rates at I, 10 and lOOK/min has also been studied on the solidification process of the alloy containing 3.5% Re. With increasing cooling rate, the crystallization start temperatures of primary y and eutectic phases decrease and the volume fraction of NbC and Ni 2 Nb increase. EPMA analysis revealed that the distribution of alloy elements in microstructure also changed depending on cooling rate. The redistribution of alloy elements during solidification was evaluated by Clyne-Kurz and Ohnaka theories.
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