Superior Strength and Ductility of 304 Austenitic Stainless Steel with Gradient Dislocations.

Qingsong Pan,Lijun Jing,Song Guo,Lei Lu,Fang Cui

doi:10.3390/nano11102613

Abstract

Materials with designed gradient nanograins exhibit unprecedented mechanical properties, such as superior strength and ductility. In this study, a heterostructured 304 stainless steel with solely gradient dislocation structure (GDS) in micron-sized grains produced by cyclic-torsion processing was demonstrated to exhibit a substantially improved yield strength with slightly reduced uniform elongation, compared with its coarse grained counterparts. Microstructural observations reveal that multiple deformation mechanisms, associated with the formation of dense dislocation patterns, deformation twins and martensitic phase, are activated upon straining and contribute to the delocalized plastic deformation and the superior mechanical performance of the GDS 304 stainless steel.

Highlights

Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of School of Materials Science and Engineering, University of Science and Technology of China, These authors contributed to this work
Traditional strengthening methodologies are generally based on the generation of various volume or planar defects, such as conventional high-angle grain boundaries (HAGBs, with misorientation angles larger than 15◦ ), and coherent twin boundaries (TBs) to resist the motion and transmission of the intra-grain dislocations [3,4]
The average size of dislocation cells or being punched, the transmission electron microscope (TEM) foils were fixed to 3 mm diameter Cu rings with a hole of diameter walls at different depths of gradient dislocation structure (GDS) was determined from TEM images on at least 700 meas0.5 mm and thinned by twin-jet polishing in an electrolyte of perchloric acid (8%), alcohol urements

Summary

Introduction

Heterostructured metals with the built-in spatially graded distribution of structural features, such as grain size [8,10], or twin thickness [11,12], spanning from nanometer at surface to microscale at core, exhibit a desirable combination of high strength and considerable ductility, which is not achieved in the non-gradient counterparts [4,7] Such superior ductility primarily originates from the progressive plastic yielding from the core to surface of the gradient nanostructures, which induces the activation of nano11102613. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations

Methods

Results

Conclusion