In-situ neutron diffraction study of a heating treatment for Nb ₃Sn ITER superconducting wires

In-situ powder neutron diffraction studies have been performed during the heating treatment of a set of Nb₃Sn wires obtained by the internal tin process. The different phases appearing during the process have been evidenced. A strong reorientation of the deformed copper and niobium metals induces an orientation on the Nb₃Sn formed. Among the phases formed, the δ-CuSn phase is decomposed at 890K to form the γ-CuSn and Nb₃Sn phases. The kinetics of these phases is in agreement with a diffusion-growth mechanism.