Deformation behavior of thermal aged duplex stainless steels studied by nanoindentation, EBSD and TEM

Liu, G.; Wang, Yihuan; Li, S.; Du, Kaiping; Wang, X.

doi:10.1179/1878641315y.0000000014

Cited by 12 publications

(21 citation statements)

References 13 publications

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“…The nanoindentation results very well coincide with measurements of other reports on bulk iron samples . The measured hardness of the ferritic matrix strongly depends on the maximum force.…”

Section: Discussionsupporting

confidence: 88%

Foams of Gray Cast Iron as Efficient Energy Absorption Structures: A Feasibility Study

et al. 2019

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Gray cast iron foams are produced using a reticulated polyurethane by using a modified investment casting process. To evaluate the attributes of the produced micro-geometries, foam segments and single struts are investigated by light and electron microscopy in 2D, and synchrotron micro-computed tomography in 3D. Mechanical properties are determined by macro/micromechanical testing and nanoindentation. In the microstructure of the gray cast iron struts, both flake-like coarse type A and locally fine undercooled type D graphite particles are observed. The distribution of the two graphite types is heterogeneous and is the likely cause for the large scatter of the mechanical properties of the single struts. The high graphite content and the resulting brittle behavior of the struts lead to strong serrations in the stressstrain curve of the foams with a negative effect on energy absorption. We found a relatively low energy absorption efficiency of below 50% as compared to 75% in 316L austenitic steel struts. The small specimen size results in scale effects which strongly influence the mechanical properties of the foams. Further improvement in the fabrication of gray cast iron foams is needed to tailor graphite distributions and optimize performance of cast iron-based foams.

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Section: Discussionsupporting

confidence: 88%

Foams of Gray Cast Iron as Efficient Energy Absorption Structures: A Feasibility Study

et al. 2019

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“…Such phenomenon was also found in the real in-situ tensile experiments of this steel [9]. As the mechanical properties of the austenite phase remain the same after long-term thermal aging [8,34,36], such an increase seen in bulk behavior can be explained by the hardening of ferrite phase during the aging process [8,34]. Former nanoindentation tests have proved that after aging at 475 • C for 2000 h, the nanohardness of ferrite increases by 65% from 3.7 to 6.1 GPa [8].…”

Section: Stress-strain Behaviorsupporting

confidence: 74%

Three-Dimensional (3D) Microstructure-Based Modeling of a Thermally-Aged Cast Duplex Stainless Steel Based on X-ray Microtomography, Nanoindentation and Micropillar Compression

Zhang

Zhu

Singaravelu

et al. 2019

Metals

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Finite element analysis was conducted on a thermally-aged cast duplex stainless steel based on the true three-dimensional (3D) microstructure obtained from X-ray microtomography experiments and using the constitutive behavior of each individual phase extracted from nanoindentation on single-crystal and bicrystal micropillar compression tests. The evolution of the phase morphology, the mechanical properties and the boundary deformation behavior during the aging process are highlighted. Quantitative analysis in terms of the distribution and evolution of the stress and strain in both the as received and aged conditions was performed. The experimental results show that aging at an intermediate temperature has a negligible influence on the morphology of the two phases in cast duplex stainless steel (CDSS). Results from simulations reveal that the mechanical behavior of this material were seriously affected by the microstructure and the mechanical properties of the individual phase and the necking deformation tend to form in the area with less large ferrite grains after aging. In addition, stress localization tends to form at the austenite/ferrite interface, in the narrow region of ferrite grains and in the small ferrite grains.

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“…The ductility was measured by the point when the specimens fractured, although the ferrite phase has the problem of thermal aging embrittlement, the volume fraction is only about 20% [34], so the fracture is mainly controlled by the austenite phase. Based on other research [11,14,32], the mechanical properties of austenite phase remain the same after the long-term thermal aging and further annealing. Thus, the ductility is similar among different aging conditions.…”

Section: Stress-strain Behaviormentioning

confidence: 79%

“…Many researchers have found that the ferrite phase shows a significant hardening through the formation of spinodal decomposition and the precipitation hardening caused by the G-phases [11,[13][14][15] during long-term thermal aging. Then after annealing at 550 • C for a short time, the mechanical properties of ferrite phase recovered to almost the same level as the unaged condition due to the dissolution of spinodal decomposition [11,14], while the mechanical properties of austenite phase remain the same with different aging conditions [11,32]. Thus, such differences on tensile stress can be explained by the evolution of ferrite hardness during the aging process.…”

Section: Stress-strain Behaviormentioning

confidence: 89%

Mechanical Properties of a Thermally-aged Cast Duplex Stainless Steel by in Situ Tensile Test at the Service Temperature

Zhang

Jing

2019

Metals

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Z3CN20.09M cast duplex stainless steel (CDSS) has been used for primary coolant water pipes in pressurized water reactors due to its excellent mechanical properties. Such pipes operate at an elevated service temperature (~320 °C) and experience issues of thermal aging embrittlement. In situ tensile tests were conducted to investigate the deformation mechanisms of Z3CN20.09M CDSS after long-term thermal aging at 475 °C for up to 2000 h in both optical microscope and scanning electron microscope at 320 °C. For the 320 °C tests, the tensile stress and other mechanical properties, e.g. the yield stress and the ultimate tensile strength, increase during the thermal aging process and recover to almost the same level as the unaged condition after annealing heat-treatment, which is caused by the formation and dissolution of precipitation during aging and anneal heat-treatment, respectively. For the slip mechanism, straight slip lines form first in the austenite phase. When these slip lines reach the austenite/ferrite interface, three kinds of slip systems are found in the ferrite phase. During the fracture process, the austenite phase is torn apart and the ferrite phase shows a significant elongation. The role of the ferrite phase is to hold the austenite matrix, thus increasing the tensile strength of this steel.

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Deformation behavior of thermal aged duplex stainless steels studied by nanoindentation, EBSD and TEM

Cited by 12 publications

References 13 publications

Foams of Gray Cast Iron as Efficient Energy Absorption Structures: A Feasibility Study

Foams of Gray Cast Iron as Efficient Energy Absorption Structures: A Feasibility Study

Three-Dimensional (3D) Microstructure-Based Modeling of a Thermally-Aged Cast Duplex Stainless Steel Based on X-ray Microtomography, Nanoindentation and Micropillar Compression

Mechanical Properties of a Thermally-aged Cast Duplex Stainless Steel by in Situ Tensile Test at the Service Temperature

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