Effect of the chemical composition on the structure and mechanical properties of alloys of the system Mn-Al-C in the magnetic region

Alloys of the Mn-Al-C system become ferromagnetic after certain heat treatments. The effect of excess phases of alloy with constant carbon content on the structure, thermal stability, and deformability of the alloy was studied. Castings were homogenized at 1150°C 2 h with subsequent cooling in air. The stability of the τ-phase forming upon cooling was evaluated from measurement of saturation magnetization, in the initial state and after annealing. An increase in the manganese content of the alloys from 68.9% to 73.5% increases the stability of the high-temperature Ε-phase, and the temperatures of the beginning and end of the Ε-τ-transformation are lowered. Enrichment with aluminum or manganese relative to the optimum leads to appearance of excess nonmagnetic η- and β-phases, lowering the level of magnetization.