Preferred orientations in the superalloy IN738LC after different aging heat treatments

Preferred orientations (POs) found in IN738LC superalloy after solutionizin g and various aging heat treatments, with different size gamma' precipitate s, were analyzed using X-ray diffraction patterns. The alloy shows a strong tendency to acquire specific preferred orientations in the different micro structures. The single phase supersaturated solid solution shows a strong { 131} PO, which changes to {111} as the solid solution is aged. Precipitates form with the cube textures. The microstructure with the fine "cooling" pr ecipitates shows the {110} PO right after the formation of the fine precipt ates and the orientation changes to the {100} cube texture with coarsening of these precipitates. Concurrent with precipitation, the matrix is found t o abandon its specific PO and acquire similar texture as the precipitate du e to its coherency with the precipitates. Only in the duplex-size precipita te microstructure the matrix and the precipitates have their individual POs , the matrix the {111} and the precipitate the {100}. This is envisioned as due to the start of dissolution of the coarsened precipitates leading to p ossible removal of any misfit strain energy at the precipitate-matrix inter face and the attendant loss of coherency. With the coarsening of the partic les through par tide agglomeration in the duplex-size precipitate microstru cture, slow development of random orientation is indicated by the XRD patte rns. The misfit between the precipitate and the matrix is found to be small , generally <0.36%, oftentimes close to zero in the case of well-developed precipitated microstructures with single PO for both the matrix and the pre cipitate phase.