Nitrogen solution in molten Fe_1−yM_y (M≡Al Mn) analysed using statistical thermodynamics

Abstract

The behaviour of N in solution in molten Fe_1−y M _y (M≡Al, Mn) was analysed using statistical thermodynamics. According to available experimental evidence, N solubility tends to be enhanced with increasing Mn content in molten Fe_1−y Mn _y N _x , but tends to be suppressed with increasing Al content in molten Fe_1−y Al _y N _x in the regime where Sieverts' rule is obeyed and no MnN or AlN precipitation takes place. Enhanced N solubility in molten Fe_1−y Mn _y N _x with increasing Mn content was concluded to be attributable to the formation of Mn–N dipoles. On the other hand, the observed suppression of N solubility with increasing Al content in molten Fe_1−y Al _y N _x was ascribed to lattice strain in the Fe_1−y Al _y sublattice induced by alloying with Al. In contrast to direct pairing between Mn and N atoms in molten Fe_1−y Mn _y N _x , no direct chemical (electronic) interaction between Al and N appeared to occur in molten Fe_1−y Al _y N _x .

MST/1257