[en] This paper presents a study of the thermal transport properties of extra-light MgB₂/Ti/Al + Al₂O₃ composite wires. The longitudinal thermal conductivity has been investigated as a function of temperature and magnetic field on wires differing only by an outer Al + Al₂O₃ sheath. The correlation between the thermal transport properties, the microstructure of the Al + Al₂O₃ sheath and the Al/Ti interface reactions provide important information for these thermally stabilized extra-light superconductors. The thermal runaways observed by the current–voltage characteristics of MgB₂/Ti/Al + Al₂O₃ wires correlate well with the conductor’s temperature affected by the thermal conductivity and the resistance of the outer sheath. (paper)