Characterization of M₂₃C₆ Carbides Precipitating at Grain Boundaries in 100Mn13 Steel

Characteristics of the formation, the interfacial structure, and the defects of M₂₃C₆ carbides in 100Mn13 steel after 1323 K (1050 °C) solution treatment and subsequent aging treatment were investigated by transmission electron microscope (TEM). The results show that M₂₃C₆ carbides precipitated on both sides of the grain boundaries. Each M₂₃C₆ carbide particle possesses a coherent interface and the cube–cube orientation relationship with the one austenite grain which M₂₃C₆ precipitated from. The orientation relationships between the M₂₃C₆ carbides and the austenite matrix were determined as follows: (1) [211]_γ \( \parallel \)[211]_M23C6, (\( 1\bar{1}\bar{1} \))_γ \( \parallel \)(\( 1\bar{1}\bar{1} \))_M23C6, (02\( \bar{2} \))_γ \( \parallel \)(02\( \bar{2} \))_M23C6, (2) [110]_γ \( \parallel \)[110]_M23C6, (\( \bar{1}1\bar{1} \))_γ \( \parallel \)(\( \bar{1}1\bar{1} \))_M23C6, (\( \bar{1} \)11)_γ \( \parallel \)(\( \bar{1} \)11)_M23C6. The M₂₃C₆ carbide also possesses an incoherent interface with the other austenite grain which the M₂₃C₆ carbide grew into by ledge mechanism. The precipitation of the M₂₃C₆ carbides along the boundaries can improve the hardness of the high-manganese steel to some extent. Besides, twinning and stacking faults were observed in M₂₃C₆ carbides. The reports about twinning and stacking faults in the M₂₃C₆ carbides have not been found.