Size Effects of the Micro-Sized Polycrystalline SUS304 Tensile Specimen Fabricated by Electrolytic Polishing Technique

Abstract

The tensile specimens with diameters less than 100 micro m were fabricated from a 0.5 mm diameter wire of polycrystalline austenitic stainless steel (SUS304) with average grain size of 166 ~m using electrolytic polishing technique. Optical, laser and scanning electron microscope observations revealed a smooth and mirrored specimen surface. Tensile tests of these specimens were carried out by the testing machine for micro-sized materials. In this study, tensile properties of the specimens with diameters smaller than average grain size of the sample were investigated. Tensile tests showed the clear yield points and gradual work hardening behaviors on the stress-displacement curves. All specimens exhibited strengths like a single crystal. The yield and tensile strengths were about 100 and 180~240 MPa, respectively. These specimens exhibited anisotropic fracture surfaces after tensile tests. Scanning electron microscope observations revealed the deformations of these specimens mainly occurred at grains placed between grain boundaries. The specimen with diameter less than or equal to about maximum grain size of the sample exhibited strength like a single crystal.