An investigation into the room temperature mechanical properties of nanocrystalline austenitic stainless steels

The present work has been conducted to evaluate the mechanical properties of nanostructured 316L and 301 austenitic stainless steels. The nanocrystalline structures were produced through martensite treatment which includes cold rolling followed by annealing treatment. The effect of equivalent rolling strain and annealing parameters on the room temperature mechanical behavior of the experimental alloys have been studied using the shear punch testing technique. The standard uniaxial tension tests were also carried out to adapt the related correlation factors. The microstructures and the volume fraction of phases were characterized by transmission electron microscopy and feritscopy methods, respectively. The results indicate that the strength of nanocrystalline specimens remarkably increases, but the ductility in comparison to the coarse-grained one slightly decreases. In addition the strength of nanocrystalline specimens has been increased by decreasing the annealing temperature and increasing the equivalent rolling strain. The analysis of the load–displacement data has also disclosed that the universal correlation of linear type (UTS = mτmax) between shear punch test data and the tensile strength is somehow unreliable for the nanocrystalline materials. The results suggest that the actual relation between the maximum shear strength and ultimate tensile strength follows a second order equation of type UTS=aτmax2-bτmax+c.

► Strength of nanocrystalline specimens follows a trend of a remarkable rise along with a small drop in ductility in comparison to the coarse-grained one.
► Universal correlation of linear type (UTS = mτmax) between shear punch test data and the tensile strength may be unreliable for the nanocrystalline materials.
► Actual relation between the maximum shear and ultimate tensile strength follows an empirical formula of UTS=0.013τmax2-25.62τmax+13049.