The occurrence of grain boundary serration and its effect on the M 23C 6 carbide characteristics in an AISI 316 stainless steel

Abstract

M 23C 6 precipitation behaviors at the grain boundaries have been systematically investigated in an AISI 316 stainless steel. It is found that the grain boundary serration occurs at the early stage of aging treatment, before the M 23C 6 carbides precipitate. The occurrence of grain boundary serration is directly dependent on heat treatment condition, which is responsible for carbide characteristics. Planar carbides (low density) are observed at the serrated grain boundaries while triangular carbides (high density) are observed at the flat grain boundaries. Additionally, grain boundary serration leads to the development of an array of carbide particles. Some of these carbide particles are in parallel orientation with one grain and some with the other grain constituting the boundary. High-resolution transmission electron microscope (HRTEM) investigations reveal the interfacial plane of planar carbide formed at the serrated grain boundary to be (11 1 ̄ ). These carbides probably possess low interfacial energy.