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

Abstract

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 °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° deviation of [001] direction, respectively, were measured for comparison. As samples were heated to 500 °C, the lattice stress of both samples gradually relaxes. With 760 MPa tension applied, the response of reflections of γ and γ’ phases were anisotropic. Compared with 0° sample, 18° 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, γ phase is divided into two conditions. The tetragonal distortion with c/a of γ⊥ channel is largest, while that of γ’ phase is small. The distortions at γ/γ’ phase boundary result in broadening the boundary of γ’ phase. In this work, a new elastic-induced lattice distortion model that enhances apprehensions to the constraint effect between γ and γ’ phases is built, which might provide the directly experimental evidence to the origin of rafting.