This research was conducted to determine the effect of the double solution heat treatment process on the hardness and microstructures of austenitic manganese steel. In the first stage of the process, the material was heated at 630°C for 25 minutes. Subsequently, the temperature was increased to 1050°C, and the material was then quenched in water. In the second stage, the material was heated at 1050°C for 60 minutes and then quenched in different quenching media, such as water, water ice, 1.5% Brine, and 3% Brine. Heat treatment improved the mechanical properties of the austenitic manganese steel. The mechanical properties were evaluated with the Brinell method as well as tensile and elongation tests. An optical microscope was utilized to observe the grain boundaries, while the fracture shape of the material was examined with an SEM. The results indicated that the quenching method was favorable in dissolving carbide and producing a more dominant austenitic phase. The highest hardness value of 219.26 BHN was achieved by the specimen quenched in water. Meanwhile, the lowest hardness value of 186.64 BHN occurred in the 1.5% Brine quenched specimen. [ABSTRACT FROM AUTHOR]