Effect of heat treatment and mechanical deformation on the structure and properties of iron-manganese alloys (10-40% Mn).

Alloys in the lower part of the range under investigation have been reported as being brittle by some authors while others find them to be as ductile as steels of the same tensile strength and suggested that the brittleness was due to high carbon and phosphorus contents. With this possibility in mind, the impurity content of the alloys used in this investigation was kept to as low a level as was practicable. The investigation has shown that although duplex structures composed of alpha plus epsilon martensite are the strongest of the series they experienced a ductile to brittle transition under impact conditions at about room temperature (20°C). With the appearance of the gamma phase in the structure at room temperature the ductility of the material improved with some loss in strength. Deformation during cold rolling was seen to aid the transformation of gamma → epsilon → alpha martensite. The ductile epsilon plus gamma structures would seem to be capable of forming the basis for high strength precipitation hardenable alloys.