한국주조공학회

The effect of interlamellar spacing on microstructural stability at high temperature was studied for unidirectionally solidified ternary Ni\;/\;Ni_3Al-Ni_3 Nb and binary Ni-Ni_3Nb eutectic composite. The interlamellar spacing of both alloy systems were varied with the growth rate according to λ^2R=constant relationship. As a result of isothermal heat treatments at high temperature it was considered that coarsening of lamellar structure was due to concentration gradient between the tip with a relatively small radius of curvature and the side of the thick lamellae with a larger radius of the opposite sign. Fault density was increased as the interlamellar spacing decreased. Therefore it is also considered that the higher coarsening rate of the specimen with the smaller interlamellar spacing was due to higher fault density. And the diference of coarsening rate between Ni\;/\;Ni_3Al-Ni_3Nb and Ni-Ni_3Nb eutectic composites was not observed when the interlamellar spacing was similar in size. This means that the presence of γ in γ\;/\;γ eutectic had no b arrier effect to diffusion through the γ matrix.