On the origin of sliver defects in single crystal investment castings

被引：102

作者：

Aveson, J. W. ^{[1
]}

Tennant, P. A. ^{[2
]}

Foss, B. J. ^{[3
]}

Shollock, B. A. ^{[3
]}

Stone, H. J. ^{[1
]}

D'Souza, N. ^{[2
]}

机构：

[1] Univ Cambridge, Dept Mat Sci & Met, Cambridge CB2 3QZ, England

[2] Rolls Royce Plc, Derby DE24 8BJ, England

[3] Univ London Imperial Coll Sci Technol & Med, Dept Mat, London SW7 2AZ, England

来源：

ACTA MATERIALIA | 2013年 / 61卷 / 14期

基金：

英国工程与自然科学研究理事会;

关键词：

Nickel alloys; Electron backscattering diffraction (EBSD); Directional solidification; Finite element analysis; STRAY GRAIN FORMATION; SEED MELT-BACK; DIRECTIONAL SOLIDIFICATION; DENDRITE FRAGMENTATION; FRECKLE FORMATION; IN-SITU; SUPERALLOYS; RECRYSTALLIZATION; MICROSTRUCTURE; ORIENTATION;

D O I：

10.1016/j.actamat.2013.04.071

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

The origin of sliver defects in seeded single crystal castings has been determined to be the deformation of dendrites in the mushy zone through microstructural characterization of a series of castings with a geometry sensitive to these defects. The extent of bending and torsion of the dendrites in the as-cast microstructure and the net misorientation was quantified from electron backscattered diffraction data using a bespoke data analysis method. At the point of initiation of the sliver defects, deformation was localized at the mould wall, indicating that these defects arise as a result of the bending moments generated by differential thermal contraction between the mould and the dendrites. The comparative susceptibilities of dendrites to deformation under converging and diverging growth with respect to the mould wall were distinguished. The experimental observations were supported by continuum finite element simulations using ProCAST (TM), which confirmed the occurrence of high stresses in the constricted channel where sliver defects form. Contrary to foundry wisdom, ancillary observations demonstrated that the oxide at the seed melt-back interface played no role. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

引用

页码：5162 / 5171

页数：10

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