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Residual Stresses, Thermomechanical Behavior and Interfaces in the Weld Joint of Ni-based Superalloys
|Oleg Barabash , Rozaliya I. Barabash , S. A. David , G E. Ice 1|
1. Oak Ridge National Laboratory (ORNL), One bethel Valley Road, Oak Ridge, TN 37932, United States
The quasi single crystalline structure formation in the Ni-based superalloy welds was characterized by means of X-ray polychromatic microdiffraction together with orientation imaging microscopy, scanning electron microscopy, and optical microscopy. Two Ni-based superalloys with different crystallographic orientations, Rene N5 and CMSX-4, were studied. Periodic dislocation structure is formed during continuous movement of the melt zone in a thin Ni-based superalloy sheet. We observed oscillations in the dislocation structure formed under such conditions at both macro and micro scales. Depending on the temperature, the formation of dislocations is accompanied by the partial or complete dissolution of ' particles in the matrix. The distribution of the dislocation density at the macroscale is due to a symmetric temperature gradient perpendicular to the direction of melt zone movement. Maximal dislocation density correlates with the interface between the heat affected and fusion zones. Within the same macro regions, oscillations of dislocation density due to grouping at the micro scale were also observed. The typical micro scale length of dislocation density oscillations is related to the dendrite size and the conditions of local melting and solidification. It is possible to decrease the probability of stray grain formation in the fusion zone and to improve the quality of the weld by applying a special thermal treatment to the base material.
Presentation: oral at E-MRS Fall Meeting 2005, Symposium H, by Oleg Barabash
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-26 21:00 Revised: 2009-06-07 00:44