AlN-assisted internal oxidation behavior in Al-containing high Mn steels

Abstract

The role of AlN on the internal oxidation behavior was investigated in Al-containing high Mn steels. Accelerated internal oxidation behavior was confirmed as Al contents increased. The sequential formation of internal oxidation and AlN + γ-matrix layers on the γ-matrix was observed in Al-containing steel after the heat-treatment in air. The former AlN + γ-matrix layer was replaced with the internal oxidation layer as the oxidation progressed. The heterogeneous nucleation of MnAl 2 O 4 on the AlN was identified in between the internal oxidation and AlN + γ-matrix layers. MnAl 2 O 4 shows the 10 1 ¯ 0 AlN / / 112 MnAl 2 O 4 and 0001 AlN / / 11 1 ¯ MnAl 2 O 4 orientation relationship with the pre-existing AlN by sharing Al atoms. The coherency between MnAl 2 O 4 and AlN and the evolution of oxides in Al-containing high Mn steels were further discussed. • The sequential oxidation behavior in Al-containing high Mn steels is clarified. • The orientation relationship between AlN precipitates and γ-matrix is determined. • Heterogeneous nucleation of MnAl 2 O 4 on AlN is identified. • HAADF-STEM analysis reveals the share of Al at the AlN/MnAl 2 O 4 interface.