Multiple Interface Structures of M₂₃C₆ carbides at Grain Boundary in an Aged 100Mn13 High Carbon High Manganese Steel

Multiple interface structures of M₂₃C₆ carbides precipitated at grain boundary in 100Mn13 high carbon high manganese steel, including the interface between the carbide particle and the matrix together with the interface between two adjacent carbides, were studied after 1050 °C solution treatment and subsequently after 475 °C aging treatment by high resolution transmission electron microscope (HRTEM) based on traditional transmission electron microscope (TEM). A growth model describing the adjacent M₂₃C₆ precipitations was proposed. The results show that precipitated carbide type is M₂₃C₆, which grows into both sides of austenite by a step growth mechanism. When two adjacent carbides precipitate along grain boundary, there are two cases as follows: If the two carbides have the same orientation relationship with the same austenite grain, they would grow independently to contact with each other to coalesce into a larger size carbide with the same orientation relationship. If the two carbides have different orientation relationships with the same austenite grain, and there is an original twinning in one carbide, they would grow independently to contact with each other to form a precipitated twinning.