Characterization of the Acicular Ferrite in Al‐Deoxidized Low‐Carbon Steel Combined with Zr and Mg Additions. Issue 11 (4th February 2016) - Min, Yi
Abstract : The influences of Mg and Zr simultaneously addition on nucleation of acicular ferrite (AF) in Al‐deoxidized low‐carbon steel have been investigated based on four steels with different Mg and Zr contents. The typical inclusions are characterized by scanning electron microscopy (SEM) and the chemical composition of the inclusions is determined by energy dispersive spectroscopy (EDS). The microstructure characteristics are examined by means of optical microscope (OM), SEM, and transmission electron microscopy (TEM). The formation of AF is demonstrated to be enhanced by the additions of Mg and Zr in the steels, and the highest volume fraction of AF is obtained in 0.0024% Mg–0.030% Zr steel. The nuclei inclusions are identified as Al2 O3 –MgO–MnS and Al2 O3 –MgO–ZrO2 –MnS multiphase particles with size in the range of 1.5–3.0 µm. Due to the number density of inclusions for 1.5–3.0 µm is relatively low, thus the volume fraction of AF is low as 18% even in 0.0024% Mg–0.030% Zr steel. Nevertheless, it is observed that these compounds are followed by Al2 O3 –MgO–ZrO2, Al2 O3 –MgO, and Al2 O3 in decreasing order of effectiveness for acicular ferrite. Abstract : The formation of acicular ferrite in the as‐casted microstructures is investigated by adding Zr and Mg into Al‐killed low‐carbon steel. The nuclei inclusions are identified as Al2 O3 –MgO–MnS and Al2 O3 –MgO–ZrO2 –MnS multiphase particles with size in the range of 1.5–3.0 μm. These compounds are followed by Al2 O3 –MgO–ZrO2, Al2 O3 –MgO, and Al2 O3 in decreasing order of effectiveness for acicular ferrite.