Damage and Crack Initiation Behavior of Duplex Stainless Steel during Cyclic Loading

2006 ◽  
Vol 324-325 ◽  
pp. 1117-1122 ◽  
Author(s):  
Guo Cai Chai ◽  
Robert Lillbacka
Keyword(s):  
Stainless Steel ◽  
Cyclic Loading ◽  
Crack Initiation ◽  
Duplex Stainless Steel ◽  
Fatigue Damage ◽  
Plastic Anisotropy ◽  
Experimental Investigations ◽  
Two Phase ◽  
Multi Scale ◽  
Deformation Hardening

Two phase metals during cyclic loading can suffer from non-uniform load or strain sharing between the phases due to elastic/plastic anisotropy. This can strongly influence the fatigue damage and crack initiation behavior. In this study, the fatigue damage and crack initiation behavior of an austenitic-ferritic duplex stainless steel with anneal/quenched and aged conditions has been studied by both experimental investigations and simulation using multi-scale material modeling. It was found, both experimentally and via simulations, that the material damage and crack initiation start in the ferrite phase in the material with the anneal/quenched condition and in either the ferrite or austenite phase in the material with the aged condition, mainly in the weakest phase if the deformation hardening is considered.

Modeling the Fatigue Damage Evolution in Welded Joints

2017 ◽  
Author(s):  
Zbigniew Mikulski ◽  
Vidar Hellum ◽  
Tom Lassen
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Damage Evolution ◽  
Threshold Value ◽  
Phase Model ◽  
Two Phase ◽  
Initiation Phase ◽  
Weld Toe ◽  
Small Cracks

The present paper presents a two-phase model for the fatigue damage evolution in welded steel joints. The argument for choosing a two-phase model is that crack initiation and subsequent crack propagation involve different damage mechanisms and should be treated separately. The crack initiation phase is defined as the number of cycles to reach a crack depth of 0.1 mm. This phase is modelled based on the Dang Van multiaxial stress approach. Both a multiaxial stress situation introduced by the acting loads and the presence of the multiaxial welding residual stresses are accounted for. The local notch effect at the weld toe becomes very important and the irregular weld toe geometry is characterized by extreme value statistics for the weld toe angle and radius. The subsequent crack growth is based in classical fracture based on the Paris law including the effect of the Stress Intensity Factor Range (SIFR) threshold value. The unique fatigue crack growth rate curve suggested by Huang, Moan and Cui is adopted. This approach keeps the growth rate parameters C and m constant whereas an effective SIFR is calculated for the actual stress range and loading ratio. The model is developed and verified based on fatigue crack growth data from fillet welded joints where cracks are emanating from the weld toe. For this test series measured crack depths below 0.1 mm are available. The two-phase model was in addition calibrated to fit the life prediction in the rule based S-N curve designated category 71 (or class F). A supplementary S-N curve is obtained by the Random Fatigue Limit Method (RFLM). The test results and the fitted model demonstrated that the crack initiation phase in welded joins is significant and cannot be ignored. The results obtained by the Dang Van approach for the initiation phase are promising but the modelling is not yet completed. The fracture mechanics model for the propagation phase gives good agreement with measured crack growth. However, it seems that the prediction of crack retardation based on a threshold value for the SIFR gives a fatigue limit that is overly optimistic for small cracks at the weld toe. The threshold value has been determined based on tests with rather large central cracks in plates. The validity for applying this threshold value for small cracks at the weld toe is questioned. As the present two-phase model is based on applied mechanics for both phases the parameters that have an influence on the fatigue damage evolution are directly entering into the model. Any change in these parameters can then be explicitly taken into account in logical and rational manner for fatigue life predictions. This not the case with the rule based S-N curves that are based on pure statistical treatment of the bulk fatigue life.

Investigation of mechanical and corrosion behavior of laser hybrid weld joint of 2205 duplex stainless steel

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Chuanbo Zheng ◽  
Cheng Zhang ◽  
Xiao Yong Wang ◽  
Jie Gu
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Duplex Stainless Steel ◽  
Base Metal ◽  
Corrosion Behavior ◽  
Welded Joints ◽  
Two Phase ◽  
Content Type ◽  
2205 Duplex Stainless Steel ◽  
Laser Hybrid

Purpose Duplex stainless steel is composed of equal amounts of austenite and ferrite, which has excellent corrosion resistance and strength. However, after the metal was welded, the ratio of austenite and ferrite in the joint is unbalanced, and secondary phase precipitates are produced, which is also an important cause of pitting corrosion in the joint. Design/methodology/approach This paper aims to study the mechanical and corrosion behavior of welded joints, by adjusting the welding parameters of laser hybrid welding, dual heat sources are used to weld 2205 duplex stainless steel. The two-phase content of different parts of the welded joint is measured to study the influence of the ratio of the two-phase on the mechanical and corrosion properties of the joint. Findings The ratio of austenite and ferrite in different welded joints has an obvious difference, and from top to bottom, the austenite content decreased gradually, and the ferrite content increased gradually. The harmful phases are precipitated in the middle and lower part of the joint. The strength of welded joints is slightly lower than that of base metal. At the same time, the fracture analysis shows that some ferrite phases are affected by the precipitate in the grain and produce quasi-cleavage fracture. The corrosion results show that the corrosion resistance of the welded joints is lower than that of the base metal, and the concentration of chloride ions affects the corrosion resistance. Originality/value In this paper, the authors use the influence of different welding processes on the two-phase ratio of the joint to further study the influence of the microstructure on the corrosion resistance and mechanical properties of the weld.

Effect of rolling deformation on microstructure and mechanical properties of 2205 duplex stainless steel with micro-nano structure

2020 ◽  
Vol 34 (25) ◽  
pp. 2050269
Author(s):  
Yuqi Mao ◽  
Yuehong Zheng ◽  
Yu Shi ◽  
Min Zhu ◽  
Saitejin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Volume Fraction ◽  
Two Phase ◽  
Corrosion Properties ◽  
Nano Structure ◽  
2205 Duplex Stainless Steel ◽  
Microstructure And Mechanical Properties ◽  
Rolling Deformation

In order to further expand the application scope of 2205 duplex stainless steel (DSS), its microstructure and mechanical properties require as much attention as its corrosion properties. In this study, 2205DSSs were prepared by aluminothermic reaction and the microstructures and mechanical behavior of the rolled alloys were analyzed. The micro-nanocrystals composite structure appears in the alloys after rough rolling with deformation of 40% at [Formula: see text]C followed by finishing rolling with deformation of 30%, 50% and 70% at [Formula: see text]C. With the increase of rolling deformation, the two-phase structure is gradually elongated, the average size of the two-phase grains is gradually increased, and some [Formula: see text] phase will change to [Formula: see text] phase, the volume fraction of [Formula: see text] phase is gradually increased, and the distribution of nanocrystals is gradually uniform. Meanwhile, the fracture mode of alloy is gradually changed from ductile fracture to brittle fracture. The strength and hardness of the alloy increase gradually.

scholarly journals Phase-Specific Strain Hardening and Load Partitioning of Cold Rolled Duplex Stainless Steel X2CrNiN23-4

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 976
Author(s):  
Nicola Simon ◽  
Maximilian Krause ◽  
Paul Heinemann ◽  
Hannes Erdle ◽  
Thomas Böhlke ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Residual Stresses ◽  
Duplex Stainless Steel ◽  
Strain Hardening ◽  
Plastic Anisotropy ◽  
Mean Field ◽  
Numerical Approach ◽  
Specific Strain ◽  
Cold Rolled ◽  
Anisotropic Phase

Multi-phase materials often times consist of constituents with high contrasts in phase-specific mechanical properties. Here, even after homogeneous plastic deformation phase-specific residual stresses develop that may affect the components behaviour in service. For numerical simulation of phase-specific residual stresses, knowledge of the particular phase-specific strain hardening behaviour is essential. In this study, the strain hardening of ferrite and austenite in cold rolled duplex stainless steel of type X2CrNiN23-4 is investigated. By means of X-ray diffraction, the phase-specific load partitioning and residual stress evolution are analysed for uniaxial load application in three directions within the sheets plane, taking into account the sheet metals phase specific anisotropy. In order to assess the necessity for experimental determination of anisotropic phase specific behaviour, the strain hardening parameters, derived from only one loading direction, are implemented in a mean-field approach for prediction of phase-specific stresses. A simplified simulation approach is applied that only considers macroscopic plastic anisotropy and results are compared to experimental findings. For all investigated loading directions, it was observed that austenite is the high-strength phase. This load partitioning behaviour was confirmed by the evolution of phase-specific residual stresses as a result of uniaxial elasto-plastic loading. With the simplified and fast numerical approach, satisfying results for prediction of anisotropic phase-specific (residual) stresses are obtained.

Dislocation Structures of Duplex Stainless Steel in Uniaxial and Biaxial Cyclic Loading

2005 ◽  
Vol 482 ◽  
pp. 179-182 ◽  
Author(s):  
Martin Petrenec ◽  
Veronique Aubin ◽  
Jaroslav Polák ◽  
Suzanne Degallaix
Keyword(s):  
Stainless Steel ◽  
Stress Response ◽  
Cyclic Loading ◽  
Slip System ◽  
Duplex Stainless Steel ◽  
Strain Amplitude ◽  
Equivalent Strain ◽  
Wall Structures ◽  
Equivalent Strain Amplitude

Austenitic-ferritic duplex stainless steel has been subjected to uniaxial and biaxial nonproportional cyclic loading with the same equivalent strain amplitude. The dislocation structures in specimens fatigued to fracture using both types of loadings were studied and compared. Uniaxial cyclic loading, both in austenitic and in ferritic grains, produces simple structures due to activation of predominantly one slip system. Non-proportional cyclic loading results in formation of cell and wall structures and thus in higher stress response of the material.

Electroplastic effect in specimens of duplex stainless steel under tension

2020 ◽  
Vol 86 (10) ◽  
pp. 41-45
Author(s):  
C. Gennari ◽  
I. Calliari ◽  
V. Stolyarov
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Pulse Duration ◽  
Direct Interaction ◽  
Electrical Current ◽  
High Energy ◽  
Secondary Phases ◽  
Electroplastic Effect ◽  
Two Phase ◽  
Corrosion Properties

Duplex stainless steels (DSSs) possess a typical biphasic microstructure consisting of equal amount of ferrite and austenite, which provides better combination of the mechanical and corrosion properties compared to the austenitic grade. Despite their good processability, they suffer from embrittlement of secondary phases in a very specific temperature range 450 – 1000°C depending on the composition. Solubilizing treatment after processing is required to obtain a perfect balance between austenite and ferrite and moreover, to dissolve any secondary phases that could have been formed during processing. This implies very high energy consumption of forming processes due to a high temperature (above 1000°C) or high power needed for the forming machines. The electroplastic effect could be used to reduce the force needed to form the material and extend the forming limits. The effect consists in direct interaction between the electrons of the electrical current and the ions of the material. The current mode (e.g., continuous current, pulsed current, pulse duration and duty cycle) plays an important role in the occurrence and the extent of the electroplastic effect. The electroplastic effect is investigated under tension in two-phase duplex stainless steel UNS S32205. Tensile tests under different current conditions (current density and frequency) are compared to room temperature tests. The best effect in terms of reduction of the ultimate tensile strength and increase in the fracture strain is achieved by introducing a multi-pulse current with the maximum density and pulse duration.

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