Effects of Withdrawal Rate on Microstructure and Segregation Behavior of Directionally Solidified Column Crystal DZ4125 Superalloy
The directionally solidified column crystal DZ4125 superalloy was prepared by means of Bridgman directional solidification.The influences of withdrawal rate on the microstructure and segregation behavior were studied.The results show that with increase of withdrawal rate,the primary and secondary dendrite spacing in the alloy gradually decreases;the γ'phase size gradually decreases,and the morphology changes from irregular cube and butterfly to regular cube;the size and amount of γ'phase in the interdendrite are higher than those of dendritic arm.The γ+γ'eutectics and carbides are mostly distributed in the interdendritic areas.With the increase of withdrawal rate,the morphology of carbides gradually changes from skeleton form into strip or small block,and the distribution is more dispersed and uniform.In directionally solidified DZ4125 superalloy,the Co and W are positive segregation elements and Al,Ti,Ta and Mo are negative segregation elements.With the increase of withdrawal rate,the segregation degree of positive segregation elements decreases,and the segregation degree of negative segregation elements increases.
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