Microscopic Observation of Inclusions related to Acicular Ferrite Formation in Steel Weld Metal

Abstract

To clarify the microstructural evolution in low carbon low alloy steel weld metal, the inclusions related to acicular ferrite formation were investigated from the crystallographic points of view.
The inclusions of each sample were prepared by focused ion beam and observed by transmission electron microscope. Further more, compositions of inclusions were analyzed by energy dispersive spectroscopy.
The inclusions related to acicular ferrite formation were multi-phase and they consisted of MnS, MnAl₂O₄ and amorphous. It was observed that these inclusions were enclosed by Ti concentrated area.
Thus it could be concluded that the Ti concentrated area of the inclusion surface would play a role for the heterogeneous nucleation of acicular ferrite.