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High manganese austenitic steel, for example Hadfield steel (13%Mn-1%C), exhibit ductile-to-brittle transition behavior related to intergranular fracture at low temperature. In this study, the influence of manganese content on low temperature toughness and fracture behavior has been investigated in high carbon and high manganese austenitic steel by means of electron microscopy, Charpy impact test and tensile test. Optimum manganese content for 0.9%C steel is 18 to 22 % to suppress the intergranular fracture and keep excellent toughness even at 77K. TEM observations of tensile-tested pieces have revealed that twin deformation, which causes stress concentration at grain boundaries, occurs also in 22%Mn-0.9%C steel as same as in Hadfield steel. This result suggests that the suppression of the intergranular fracture in 22% Mn-0.9% steel is due to the higher grain-boundary fracture strength of 22% Mn-0.9% steel than that of Hadfield steel.
