Gradient Microstructure Design in Stainless Steel: A Strategy for Uniting Strength-Ductility Synergy and Corrosion Resistance.

Qiong He,Yu Zhai,Ming-Sai Wang,Chong-Xiang Huang,Feng-Jiao Guo,Wei Wei,Yan-Fei Wang

doi:10.3390/nano11092356

Qiong He, Yu Zhai + Show 5 more

Open Access

https://doi.org/10.3390/nano11092356

Copy DOI

Abstract

Martensite transformation and grain refinement can make austenitic stainless steel stronger, but this comes at a dramatic loss of both ductility and corrosion resistance. Here we report a novel gradient structure in 301 stainless steel sheets, which enables an unprecedented combination of high strength, improved ductility and good corrosion resistance. After producing inter-layer microstructure gradient by surface mechanical attrition treatment, the sheet was annealed at high temperature for a short duration, during which partial reverse transformation occurred to form recrystallized austenitic nano-grains in the surface layer, i.e., introducing extra intra-layer heterogeneity. Such 3D microstructure heterogeneity activates inter-layer and inter-phase interactions during deformation, thereby producing back stress for high yield strength and hetero-deformation induced (HDI) hardening for high ductility. Importantly, the recrystallized austenitic nano-grains significantly ameliorates the corrosion resistance. These findings suggest an effective route for evading the strength–ductility and strength–corrosion tradeoffs in stainless steels simultaneously.

Highlights

Austenitic stainless steels are the most common workhorse material for structural applications in corrosive circumstances [1,2,3]
When the annealing time is increased to 20 s, i.e., for the SA20s gradient structure, the yield strength is still twice that of the homogeneous coarse-grains (Figure 5a), but their corrosionresistance resistance is almost comparable. These results suggest that the un corrosion is almost comparable
The challenge challenge can can be be overcome overcome by by designing designing gradient gradient microstructure with partial austenitic nano-grains in the surface layer. Such gradient structure be syntheaustenitic in the surface layer

Summary

Introduction

Austenitic stainless steels are the most common workhorse material for structural applications in corrosive circumstances [1,2,3]. In practical engineering, the available stainless steels are generally composed of homogeneous austenitic coarse-grains (CG) and display limited yield strength. The yield strength of hot forged commercial 301 stainless steel is only about 205–380 MPa, which is far weaker than the highstrength steels strengthened by precipitates and/or heterogeneous phases [4]. To minimize material cost and improve engineering safety in extreme service conditions, advanced high-strength stainless steels with promising ductility and corrosion resistance are highly desirable. This presents a new challenge for material developers. Recent advances in microstructure design frequently found that this tradeoff can be largely overcome by purposely deploying trans-scale heterogeneous microstructure, such as designing multimodal [6,7], harmonic [8,9], gradient [10,11,12,13,14], laminate and lamella structures [15,16,17,18,19]

Methods

Results

Conclusion