In-situ observation of inclusion agglomeration characteristics in high-manganese and high-aluminum steels with different Mn and Al contents

• In-situ observation is applied to directly reveal the agglomeration behavior and evolution of inclusions in high-manganese and high-aluminum steels, realizing the visualized characterization of inclusion agglomeration. • The in-situ observational results are combined with theoretical modeling of inclusion capillary forces, revealing the effect of the changes in interface properties caused by variation of Mn and Al contents on agglomeration of inclusions. • A quantitative critical relationship between Mn and Al contents was established, which dominates the sequence of competitive agglomeration of inclusions. Elucidating the agglomeration behavior of inclusions is critical for optimizing the quality of high-manganese and high-aluminum steels. This study predicted the precipitation behavior of inclusions using thermodynamic modeling. Six experimental groups with different Mn and Al contents were designed to obtain specific inclusions, and their agglomeration was observed in situ via confocal laser scanning microscopy (CLSM). Capillary forces were quantified using a theoretical model. The results showed the agglomeration tendency order: AlN (in Fe-30Mn-6Al melt) > AlN (in Fe-30Mn-3Al melt) > AlN (in Fe-10Mn-3Al melt) > Al 2 O 3 (in Fe-10Mn-0.2Al melt) > Al 2 O 3 (in Fe-30Mn-0.2Al melt) > Al 2 O 3 (in Fe-30Mn-0.5Al melt). With increasing Al content, the capillary force of Al 2 O 3 inclusions first increased from 5.75 × 10 -19 N to 6.22 × 10 -19 N and then decreased to 1.34 × 10 -19 N. A similar trend occurred with rising Mn content: from 5.75 × 10 -19 N to 6.52 × 10 -19 N, then to 6.01 × 10 -19 N. In contrast, the capillary force of AlN inclusions continuously increased from 4.1 × 10 -19 N to 8.29 × 10 -19 N with higher Mn and Al contents. A critical relationship between Mn and Al contents, which determines the transition in dominant capillary force, was established: y ( M n , mass % ) = - 31.38 x ( A l , mass % ) + 97.27 . This study provides theoretical guidance for regulating inclusion size distributions in high-manganese and high-aluminum steels.