Initial Deformation Behaviors in Lean Duplex Stainless Steel

Rosa Kim,Cheoljun Bae,Jongryoul Kim

doi:10.3390/met10070936

Abstract

The deformation behaviors of the austenite phase in lean duplex stainless steels were investigated through uniaxial tension tests with different amounts of deformation. Microstructural analysis showed that in the initial deformation stage the deformation in austenite grains had a predominant effect on the strain hardening behavior of the LDX-2101 steel. The initial deformation in the austenite grains was found to be mainly accommodated by the formation of stacking faults. As the deformation increased further, mechanical twins were generated by the initial stacking faults and sequentially interacted with dislocations to accommodate the strain. The analysis of dislocation behavior revealed that the deformation twinning process followed the three-layer twin formation mechanism.

Highlights

Duplex stainless steel (DSS) is a type of stainless steel that usually consists of a mixed microstructure of austenite and ferrite phases in approximately equal proportions
It should be noted that the mechanical properties of DSSs cannot be explained by analyzing the simple average properties of single-phase austenite or ferrite steels because that would not take into account the residual or interaction stress between the ferrite and austenite phases [6]
The results suggest that the twinning mechanism in austenite has an important role in the deformation mechanism of steels with austenite

Summary

Introduction

Duplex stainless steel (DSS) is a type of stainless steel that usually consists of a mixed microstructure of austenite and ferrite phases in approximately equal proportions. The ferrite (body centered cubic (bcc) structure) primarily deforms by dislocation slip involving various slip systems, driven by high stacking fault energy (SFE) [1,2,3]. The austenite (face centered cubic (fcc) structure) has multiple deformation modes, including dislocation slip, mechanical twinning, and ε/α’ martensitic transformation [1,2,3,4,5,6,7,8,9,10,11,12]. Because the austenite tends to have more deformation structures than the ferrite, the deformation behaviors of DSSs can be strongly dependent on the deformation mode of the austenite. It should be noted that the mechanical properties of DSSs cannot be explained by analyzing the simple average properties of single-phase austenite or ferrite steels because that would not take into account the residual or interaction stress between the ferrite and austenite phases [6]

Methods

Results

Conclusion