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

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.

Superior Yield Strength and High‐Tensile‐Toughness Matching of Medium‐Mn Steel with Gradient Structure Developed by Cyclic Torsion

“…The cyclic‐torsion treatment is referred to as a repeatedly imposed gradient plastic deformation process, where the one end of sample is fixed, and the other end is rotated for a few cycles at a specific angle. [ 47 ] In this study, rotating forward by 20° and then reverse movement at 20° was defined as one cycle. Torsion numbers of 20, 60, and 80 cycles at a torsional rate of 0.25 rpm were imposed to introduce different sample‐level gradient structure, which were designated as CT20, CT60, and CT80, respectively.…”

The Influence of Tempering Parameters on the Microstructure, Mechanical Property, and the Corresponding Strengthening Mechanism of Metastable 301 Austenitic Stainless Steel

“…There are roughly two methods for refining grains, including crystal self‐growth [ 7 ] and severe plastic deformation (SPD), [ 8 ] and SPD is commonly used. Pan et al [ 9 ] used the cyclic torsion treatment to obtain austenitic steel with gradient dislocation structure, enhancing the yield strength to 500 MPa. Karavaeva et al [ 10 ] obtained a uniform ultrafine‐grain austenitic steel though equal‐channel angular pressing and rolling, and the 1700 MPa yield strength and 11% fracture elongation were obtained.…”

Synthesis and deformation mechanics of gradient nanostructured materials

“…Recently, a simple, yet efficient cyclic-torsion (CT) treatment without any surface tooling was successfully developed to introduce novel sample-level gradient nanoscale stable dislocation structures with low-angle boundary misorientations (GDS, Figs. 1c and 1g) with a length scale spanning 6 magnitudes from millimeter to nano scale in engineering materials, such as 304 stainless steel (15) and high entropy alloy (HEA) (11). In particular, the initial grain structure, including grain size and morphology, is unchanged from the surface to the core, which is fundamentally distinct from the GNG structure with severely-refined grain size.…”