Application of electromechanical impedance technique in the monitoring of sigma phase embrittlement in duplex stainless steel

Silva, David D.S.; Sobrinho, José Marques Basílio; Souto, Cícero da Rocha; Gomes, Rodinei Medeiros

doi:10.1016/j.msea.2020.139457

Cited by 26 publications

(16 citation statements)

References 30 publications

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“…The precipitation of the σ phase led to the formation of γ 2 in a process defined as eutectoid decomposition (α → σ + γ 2 ); as seen in Figure 2c. These results are in agreement with previously studies [29,30].…”

Section: Structural Morphological and Mechanical Characterizationsupporting

confidence: 94%

“…The solubilized specimen had a large %RA, about 57%, while the specimen aged for 180 min exhibited a %RA below 15%, showing a brittle behavior. This is due to the increased amount of the σ phase [27,29].…”

Section: Structural Morphological and Mechanical Characterizationmentioning

confidence: 99%

“…The effect of the sigma phase on mechanical properties deserves to be studied, since a small fraction of this phase affects ductility and toughness [27,28]. Recently, Silva et al [29,30] investigated the use of an electromechanical impedance (EMI) technique and low-field magnetic analysis (LFMA) in the monitoring of sigma phase embrittlement in DSS, in order to assess modifications in the microstructure of thermally degraded 2205 DSS at 800 • C for different time intervals. The authors confirmed that small σ contents (about 6%) promoted a considerable decrease of approximately 63% of toughness in DSS.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Microstructural Changes on Mechanical and Electrochemical Corrosion Properties of Duplex Stainless Steel Aged for Short Periods

et al. 2020

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This work reports the effects of crystallographic changes due to the secondary phases, in particular sigma (σ), on the mechanical properties and electrochemical behavior of thermally aged duplex stainless steel (DSS). Structural, morphological, mechanical, and electrochemical characterizations were performed. Sigma phase content increased with increasing aging treatment time. It had a lamellar-like shape, as observed by electron backscatter diffractometry (EBSD). Its presence directly damaged mechanical properties. The corrosion assessment included electrochemical impedance spectroscopy (EIS) in 1 M NaCl solution at temperatures of 25, 40, and 65 °C. EIS results demonstrate that an increase in the σ phase content decreased the corrosion resistance (21.1–0.8, 3.5–0.3, and 3.1–0.2 kΩ cm2 at 25, 40, and 60 °C, respectively).

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Section: Structural Morphological and Mechanical Characterizationsupporting

confidence: 94%

Section: Structural Morphological and Mechanical Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Effect of Microstructural Changes on Mechanical and Electrochemical Corrosion Properties of Duplex Stainless Steel Aged for Short Periods

et al. 2020

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“…Carbides M 7 C 3 (M=metal) precipitate between 950 ºC and 1,050 ºC in grain boundaries, and M 23 C 6 is formed below 950 ºC 10 . Sigma is an intermetallic, non-magnetic, and very hard phase (σ), which causes embrittlement when precipitated in solid state between 600 and 950 ºC with loss of toughness [10][11][12] . In DSS, it preferably nucleates at the α/γ interface, which is incoherent with the matrix duplex; precipitation occurs in raw double-cast stainless steels and can consume the entire ferrite phase, represented by reaction α = σ + γ* (eutectoid), where γ* is a secondary austenite containing less Mo and Cr than untransformed austenite [11][12][13][14] .…”

Section: Introductionmentioning

confidence: 99%

Dilatometric Cycles in the Study of Precipitation of Intermetallic Phases in Duplex Stainless Steels

et al. 2020

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Duplex stainless steels (DSS) are used in offshore platforms due to their good properties resulting from the combination of two phases, namely austenite and ferrite. Secondary intermetallic phases, such as alpha prime (α´) and sigma (σ), which are harmful, can be formed at temperatures above 400 °C, or by a casting process. This study investigates the formation of sigma phase by thermal cycles running in a dilatometer (800 °C, 850 °C, 900 °C and 1,000 °C) for 1h, and at 850 °C for 3h and 7h. The optical microscopy of the DSS microstructure subjected to 800, 850 and 900 °C for one hour revealed a small fraction of σ phase with nucleation in the contour of ferrite/austenite phases, and tests by ferritoscope indicated a decrease (~4%) in a magnetic fraction (ferrite). However, samples subjected to dilatometric cycles at 850 °C for 3 hours showed an 18% decrease in the magnetic phase and quantitative metallography revealed a 33% fraction of σ phase precipitated in the ferrite phase. Tests conducted at 850 ºC for 7 hours indicated a high fraction of σ phase precipitated (approximately 50%), starting in the grain boundary, austenite/ferrite, and advancing in ferrite grain.

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“…Their research well validates the effectiveness and applicability of the EMI method in real-time monitoring of cement stiffness degradation under compression loadings. Silva et al [ 12 ] applied the EMI technique in the monitoring of sigma phase embrittlement in duplex stainless steel. This method is considered as a nondestructive test, presents accurate results with high sensitivity and reliability providing a capacity of determining sigma phase embrittlement, and has promising application potential in this and other materials.…”

Section: Introductionmentioning

confidence: 99%

Electromechanical Impedance Model for Free 1D Thin-Walled Piezoelectric Ceramics with a Novel Derivation

et al. 2020

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The electromechanical impedance model of the piezoelectric ceramics in a free state can be used for screening and quality control in the structural health monitoring community, but the derivation process of the existing model is usually complicated. This paper describes a novel theoretical derivation methodology based on the assumption of zero-stress on the free boundary of the one-dimensional transducer, which can simplify the derivation of the model to a large extent. To assess the accuracy of the model, a signal processing method based on frequency shifting transformation and the Pearson correlation coefficient is also proposed to calculate the similarity between theoretically predicted and experimentally measured data. Two different piezoelectric ceramics were used in experiments to verify the effectiveness of the model. Experimental results convincingly demonstrate that the assumption proposed in this paper possesses good feasibility for one-dimensional thin-walled piezoelectric ceramics and the model has excellent precision.

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Application of electromechanical impedance technique in the monitoring of sigma phase embrittlement in duplex stainless steel

Cited by 26 publications

References 30 publications

The Effect of Microstructural Changes on Mechanical and Electrochemical Corrosion Properties of Duplex Stainless Steel Aged for Short Periods

The Effect of Microstructural Changes on Mechanical and Electrochemical Corrosion Properties of Duplex Stainless Steel Aged for Short Periods

Dilatometric Cycles in the Study of Precipitation of Intermetallic Phases in Duplex Stainless Steels

Electromechanical Impedance Model for Free 1D Thin-Walled Piezoelectric Ceramics with a Novel Derivation

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