Abstract Encapsulated microstructures of austenite and co-precipitates were formed using a designed tempering and double partitioning (TDP) heat treatment based on the precipitation-induced localized austenite reversion in a medium manganese (Mn) steel. The retained austenite in TDP steel showed better mechanical stability due to the preferable coherency of austenite/ferrite interfaces and a greater capability of geometrically necessary dislocations (GNDs) accommodation. The outstanding cryogenic tensile mechanical properties were attributed to the heterogeneous capsule structure of the austenite in the TDP steel, in which the e-martensite transformation has been suppressed and the austenite were segmented by the α’-martensite during deformation.