Microstructural evolution and its impact on mechanical and corrosion performance of 316L ODS steels processed by mechanical alloying and pulse plasma sintering

In this study, austenitic oxide dispersion-strengthened (ODS) steels were fabricated by mechanical alloying (MA) of 316L stainless steel with 1 wt.% of either nano- or micro-sized Y 2 O 3 particles, followed by pulse plasma sintering (PPS). The effects of MA duration (5, 10, and 50 hours) and Y 2 O 3 particle size on the microstructure, mechanical properties, and corrosion resistance were systematically investigated. The morphology and size of the alloyed powder particles were strongly influenced by MA parameters: longer milling times produced finer, though more irregularly shaped, particles. Increasing the milling duration led to a higher fraction of fine grains and elevated dislocation densities, indicating grain refinement driven by discontinuous recrystallization. Mechanical testing revealed that strength was primarily controlled by the MA duration. Samples milled for 50 h reached the highest strength regardless of Y 2 O 3 particle size, owing to the combined effects of grain refinement and Orowan strengthening. This strength gain, however, was accompanied by a loss in ductility. Corrosion behavior, assessed via electrochemical methods and salt spray tests, was strongly dependent on internal strain and grain boundary characteristics. The best corrosion resistance was observed in samples milled for 5 h, which had lower dislocation densities and smaller grain boundary areas. In contrast, prolonged milling (50 h) increased grain boundary density and misorientations, accelerating corrosion—particularly in steels reinforced with micro-sized Y 2 O 3 particles.