Effect of withdrawal rate transition on microstructural features of a single crystal Ni‐based superalloy. Issue 6 (18th May 2017)

• Record Type: Journal Article
• Authors: Sadeghi, Fazlollah; Kermanpur, Ahmad; Heydari, Davoud; Bahmani, Majid
• Is Part Of: Crystal research and technology. Volume 52:Issue 6(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-05-18
• Subjects: Single crystal solidification -- Ni‐based superalloys -- Withdrawal rate -- Dendrite arm spacing -- Crystal orientation; Crystallography -- Periodicals; 548
• DOI: 10.1002/crat.201700012
• Languages: English
• ISSNs: 0232-1300

Abstract

Abstract : The effect of the withdrawal rate transition on various microstructural features of a single crystal Ni‐based superalloy was investigated. The dendrite morphology, spacing and orientation were studied using optical microscopy, EBSD and RO‐XRD techniques. The results showed a gradual decreasing trend in PDAS and SDAS by a sudden increase of the withdrawal rate. The dendritic growth was found to be history‐dependent and its dependency is related to the solidification condition. The withdrawal rate transition was shown to be influential on crystallographic misorientation such that, a more severe transition would result in a higher misorientation change. Abstract : The effect of withdrawal rate transition during Bridgman directional solidification on microstructural aspects of a single crystal Ni‐based superalloy was investigated under both constant and changing withdrawal regimes. Variations of primary and secondary dendrite arm spacing (PDAS and SDAS, respectively) and crystal orientation were investigated using optical microscopy and electron backscattered diffraction (EBSD) techniques. The results showed a gradual decreasing trend in PDAS and SDAS by sudden increasing of withdrawal rate. Changes on PDAS was quantified as history‐dependent such that for a given secondary withdrawal rate, a higher PDAS was found for a lower initial withdrawal rate. The withdrawal rate transition showed a direct influence on crystal orientation.