TEM analysis of 2205 duplex stainless steel to determine orientation relationship between M23C6 carbide and austenite matrix at 950 °C

Microstructures of 2205 duplex stainless steel were examined using transmission electron microscopy. During isothermal heating at 950 °C, M23C6 carbide was formed on the austenite grain boundaries with two types of morphologies: “larva” and “triangle”. The orientation relationship between the M23C6 carbide and the austenite matrix is cubic-to-cubic. In addition, these two types of precipitates have a twin relationship with each other. Based on the STEM-EDS data, the silicon content of triangle M23C6 carbide is higher than that of the larva M23C6 carbide, revealing that the silicon content in the M23C6 carbide plays an important role in determining the orientation relationship between the M23C6 carbide and the austenite matrix.