Dendritic segregation in heat-resistant nickel alloys
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Hafnium has the highest segregation coefficient in the nickel alloys investigated. In the presence of hafnium, molybdenum reverses the sign of segregation. Vanadium is evenly distributed in axial and interaxial areas and segregation is negligible.
Raising the rate of directional solidification from 0.4 to 4 mm/min leads to a substantial increase in the dendritic heterogeneity of the alloys.
Changing the rate of directional solidification in the range of 4–80 mm/min leads to a negligible change in the segregation coefficient of the alloys, but leads to refining of the dendritic structure, which has a positive effect on the fatigue strength.
Uneven solidification conditions and segregation of alloying elements affect the formation and composition of the eutectic precipitated in interaxial areas. Because of this, the eutectic is enriched in elements concentrating in interaxial areas and impoverished in elements concentrating in the axes of dendrites.
KeywordsFatigue Nickel Vanadium Molybdenum Fatigue Strength
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