Thermodynamics formation of oxides in laser powder bed fusion processed aluminum-deoxidized maraging steel and their effects on toughness

• PREP powder with lower oxygen content (0.016wt%) produced finer and more dispersed Al2O3 inclusions than VIGA powder (0.034wt%), leading to improved toughness. • Impact toughness of PREP specimens was 138 J at 23°C and 65 J at −196°C, representing increases of 53.3% and 47.8% over VIGA specimens, respectively. • Lower oxygen content reduces the nucleation barrier, promoting lower-temperature nucleation and finer oxide distribution in L-PBF maraging steels. • A thermodynamic model was developed to predict the size and number density evolution of oxide inclusions under different oxygen levels, aiding powder design and process control.