Abstract
Ultrafine-grained (UFG) materials show increased strength and hardness, but usually exhibit limited ductility. It is imperative to improve the mechanical properties in terms of ductility and toughness. Bimodal grain size distribution is an effective way to retain high strength, while improving ductility. SUS304L water-atomized powders were mechanically milled (MM) and consolidated by hot isostatic pressing (HIP). A bimodal structure could be observed in the sintered compacts. After sintering of the water-atomized powders, many silicon oxide particles disperse uniformly in the ultrafine-grained regions and at the UFG/CG interface. The ultrafine-grained regions improve the strength and hardness, while the coarse-grained regions provide work-hardening to maintain significant uniform plastic deformation. However, compared with bulk materials without silicon oxide particles, the silicon oxide particles existing in bimodal structure compacts lead to impaired inter-particle bonding, as reflected in markedly-worsened elongation. The effects of silicon oxide particles on deformation and fracture behavior of bimodal structure compacts are investigated. To obtain enhanced mechanical properties, the surface silicon oxide must be reduced.
