DENDRITE ARM SPACINGS AND MICROSEGREGATIONS IN AND ORIENTATED SINGLE CRYSTAL SUPERALLOYS DD407

Abstract

Single crystal superalloys DD407 with〈001〉and〈011〉orientations were produced with seeding technique by using the liquid metal cooling Bridgman furnace.The dendrite arm spacings (DAS) and microsegregations in the single crystal superalloys with〈001〉and〈011〉orientations were investigated.The results indicated that increasing the deviation angle from〈001〉orientation or decreasing the deviation angle from〈011〉would increase the dendrite arm spacing.In addition,DAS of single crystal grown along〈011〉orientation is obviously greater than that of〈001〉orientation for side-branching.EMPA results showed that the positive segregation elements Al,Ti and Ta enriched in the interdendritic region,and the negative segregation element W enriched in the dendrite core.The microsegregation in the single crystal with〈011〉orientation paralleled to the sample axis is the lightest. It is found that not only the DAS but the mechanism of dendrite evolution and arrayed pattern of dendrite affect the degree of microsegregation.