Residual stresses in a welded superalloy disc: Characterization using synchrotron diffraction and numerical process mode
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I. INTRODUCTION
DURING a fusion welding process, the workpiece receives a considerable heat input from the heat source, which might be an electric arc or an electron beam. Localized melting of the weld pool occurs, and the surrounding region undergoes thermal expansion. The surrounding material remains cool and this, together with the fixturing arrangement, provides considerable constraint, particularly as cooling begins, and thermal contraction starts to set in. For most alloys and processes, the conditions are such as to induce plastic deformation in the weld and the surrounding heataffected zone. Consequently, a residual-stress field is set up, and weld-induced distortions occur. Shrinkage, warping, and buckling are commonplace. M.V.R.S. JENSEN, formerly with the Department of Materials Science and Metallurgy/Rolls-Royce University Technology Centre, University of Cambridge, Cambridge, United Kingdom, carried out this research while on leave from the Department of Production, Aalborg University, Fibigerstraede 16, 9220 Aalborg, Denmark. D. DYE, formerly with the Department of Materials Science and Metallurgy/Rolls-Royce University Technology Centre, University of Cambridge, is Postdoctoral Fellow, Neutron Program for Materials Research, National Research Council, Chalk River, ON, Canada K0J 1J0. Contact e-mail: [email protected] K.E. JAMES, Postdoctoral Research Associate, and A.M. KORSUNSKY, Lecturer, are with the Department of Engineering Science/Rolls-Royce University Technology Centre, University of Oxford, Oxford, OX1 3PJ United Kingdom. S.M. ROBERTS was formerly with the Department of Materials Science and Metallurgy/Rolls-Royce University Technology Centre, University of Cambridge, Cambridge CB2 3QZ United Kingdom. R.C. REED, formerly with the Department of Materials Science and Metallurgy/Rolls-Royce University Technology Centre, University of Cambridge, is Professor and Canada Research Chair, is with the Department of Metals and Materials Engineering, University of British Columbia, BC, VGT 1Z4 Canada. Manuscript submitted August 31, 2001. METALLURGICAL AND MATERIALS TRANSACTIONS A
From a practical point of view, it is important to have an appreciation of the residual-stress field, which is induced in welded joints, for a number of reasons. First, the structural integrity of a welded component is very strongly affected by the presence of residual stresses; this is particularly the case for the mechanical performance in fatigue. Second, the residual stresses can cause defects, such as microfissuring and cracking, such that a weld may not be of sufficient quality for entry into service. Finally, the residual stresses might induce distortions that are so severe that dimensional tolerances are exceeded and component reworking is required. Ideally, one would like a good understanding of the manner in which the residual-stress state is induced and a quantitative estimate of it. The present article is concerned with the analysis of the residual-stress state induced in a welded assembly of the superalloy IN718
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