On the Formation of Coarse Niobium Particles in Microalloyed HSLA Steels

摘要

Coarse particles containing Nb and Ti were observed in microalloyed HSLA steels. The coarse particles in HSLA steels have been shown to be the source of various discontinuities and initiate premature failure. Previous studies have speculated that the coarse particles observed in HSLA steels are undissolved phases originating from ferroalloy additions such as FeNb. In this study, the chemical composition and crystal structure of thermodynamically stable phases in FeNb are characterized using EDS, EBSD, EELS, and SAD. These phases are shown to have a different chemistry and structure as compared to the coarse particles observed in microalloyed HSLA steels.