In-situ tensile study of annealed bimodal nano/micro grained medical 316L stainless steel

Abstract

The tensile fracture behavior of the annealed 316L austenitic stainless steel at room temperature was studied by in-situ tensile platform loaded on the field emission scanning electron microscope with 4.2e−4 s−1 of initial strain rate. The results showed that tensile strength and yield strength of annealed specimens of 316L for annealing treatment for 28 h at 800 °C were higher than those of as-cast specimens. After annealing, microstructures of the specimens were mainly micron crystals. When the applied loading was 162 MPa, initiation source appeared. Loading reached 380 MPa, main cracks continued to expand and became deeply, and specimen yielded at this time. When loading reached up to 533 MPa, specimens reached the maximum stress value. After breaking completely, included angle was approximately 70° between fracture surface and direction of tensile axis. The composition of the fracture was more pure and continuity of the matrix was good. This showed that micro/nanostructure stainless steel prepared by aluminothermic reaction casting, which could improve the mechanical properties through controlling size of nanocrystalline and microcrystalline austenite grains and their volume fraction.