Elastic tension induced lattice distortions in DD10 single crystal nickel-based superalloy at 500 ℃/760 MPa using in situ neutron diffraction

摘要

A newly-developed in situ neutron diffraction method has been employed to search elastic tension induced lattice distortions in DD10 single crystal nickel-based superalloy under tensile condition of 500 degrees C/760 MPa. Multiple lattice reflections, viz., {002}, {003}, {220}, {311} were in situ measured. Two samples which were stretched along [001] direction and 18 degrees deviation of [001] direction, respectively, were measured for comparison. As samples were heated to 500 degrees C, the lattice stress of both samples gradually relaxes. With 760 MPa tension applied, the response of reflections of gamma and gamma' phases were anisotropic. Compared with 0 degrees sample, 18 degrees sample resulted in distinguishable results. Due to the large extra stress, the mismatch along [001] direction is much negative, whereas that perpendicular to [001] get slightly positive. Owing to the different stress states, gamma phase is divided into two conditions. The tetragonal distortion with c/a of gamma(perpendicular to) channel is largest, while that of gamma' phase is small. The distortions at gamma/gamma' phase boundary result in broadening the boundary of gamma' phase. In this work, a new elastic-induced lattice distortion model that enhances apprehensions to the constraint effect between gamma and gamma' phases is built, which might provide the directly experimental evidence to the origin of rafting.