Effect of grain size and intergranular oxides at prior powder-particle boundaries on the mechanical properties of 316 stainless steels by powder metallurgy hot isostatic pressing: strengthening versus embrittlement

Abstract The mechanical performance of powder metallurgy metallic materials is closely tied to their microstructures, particularly grain size and precipitation. In this study, the microstructure and mechanical properties of AISI 316 stainless steels with oxide precipitation manufactured by powder metallurgy hot isostatic pressing (HIP) were investigated. The results show that the ball milling, as a pre-processing step for metallic powders, significantly influences the final microstructure and mechanical response. Steels consolidated from the ball-milled powders exhibit finer grains (average size $$\overline{d }$$ = ~6 μm) and micron-scale oxide precipitates, while those from mixed powders show coarser grains ($$\overline{d }$$ = ~14 μm) and finer nano- to submicron-scale oxides. The fine-grained steel displays higher yield strength (276 MPa vs 238 MPa) but lower tensile elongation (11% vs 51%) compared to the coarse-grained counterpart. The significantly low tensile ductility of the fine-grained steel is attributed to strain localization caused by dislocation interactions with coarse oxide precipitates. In contrast, the finer precipitates in the coarse-grained steel promote sustainable strain hardening and homogeneous deformation, enhancing ductility. These findings demonstrate a promising strategy to overcome the strength–ductility trade-off in HIP-processed alloys by tailoring oxide precipitate size and grain structure for improved strain hardening and ductility.