Effects of section sizes on microstructure of a nickel-base single crystal superalloy have been studied by making directly thin-wall specimens whose wall thicknesses are 0.8,1.5mm and 2.5mm by using the Bridgmen procedure.The results show that,with the decrease of section size,the primary dendritic arm spacing of thin-wall specimen decreases,and the secondary dendritic arm spacing increases firstly and then decreases;comparing with the standard specimen(φ15mm),the size of γ′phase particles in the dendritic core decreases but that of interdendritic changes slightly,the volume fraction of γ/γ′eutectic also decreases obviously.EDS analysis shows that microsegregation of thin-wall specimens has been suppressed comparing with the standard specimen,but the microsegregation of specimens with different thickness isn’t obvious.Furthermore,γ/γ′ eutectic of thin-wall specimens was ruled out basically after vacuum solid-solution treatment,but for φ15mm specimen there remains a small amount γ/γ′eutectic.
Key words
section size /
nickel-base single crystal superalloy /
microstructure /
microsegregation
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References
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