Study on the microstructural evolution of different component alloys consisting of B2-NiSc intermetallics

Zhipeng Yuan, HongBao Cui, Yatao Chang, XueFeng Guo

Abstract


Ni-50%Sc and Ni-51%Sc alloy were prepared with a vacuum arc smelting and water cooled copper mold suction-casting machine. The results showed that the two component alloys consisted of the primary phase B2-NiSc and lamellar (Ni2Sc+NiSc)eutectic due to the loss of Sc during
melting. Two groups of alloys underwent (970 ℃, 72 h) homogenization heat treatment, and spherical or plate shape Ni2Sc particles were dispersed on the B2-NiSc matrix. With the increase of Sc content from
50% to 51%, the amount of the second phase in the alloy decreases, the microstructure becomes uniform, and the grain gradually changes from long bar to a spherical particle. According to the Jackson boundary theory, the Jackson factor α of B2-NiSc =0.5 < 2, so the interface is rough, which explains that the growth pattern of the B2-NiSc phase is a
non-faceted growth. It is consistent with the dendritic growth pattern of the B2-NiSc phase, which is observed from the experiment. After a long
heat treatment, the number of vacancies decreases and the microstructure became uniform. The loss rate of Sc in rapidly quenched solidification was higher than that after the heat treatment.

Keywords


intermetallics; microstructural evolution; second phase; rapid solidification, (Ni2Sc+NiSc) eutectic

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ISSN 1330-9587 (Print), ISSN 1849-0433 (Online)

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