Effect of Plastic Deformation on the Isothermal FCC/HCP Phase Transformation during Aging of Co-27Cr-5Mo-0.05C Alloy

2007 ◽  
Vol 560 ◽  
pp. 23-28
Author(s):  
A. Mani-Medrano ◽  
Armando Salinas-Rodríguez
Keyword(s):  
Plastic Deformation ◽  
Martensitic Transformation ◽  
Tensile Deformation ◽  
Internal Stresses ◽  
X Ray Diffraction ◽  
Thermally Activated ◽  
Prior Plastic Deformation ◽  
Last Stage ◽  
Isothermal Martensitic Transformation

The effects of tensile deformation on the amount of hcp phase formed during a 3 hour isothermal aging at 800 °C is studied using in-situ X-ray diffraction and scanning electron microscopy. It is shown that the start of the isothermal martensitic transformation during aging of this material is delayed by prior plastic deformation. Nevertheless, the total amount of hcp phase present in the microstructure at the beginning of aging increases at a continuously decreasing rate due to stress-assisted transformation. This behavior is attributed to the relieving of internal stresses produced by plastic deformation prior to aging. Finally, during the last stage of aging, the amount of hcp phase in the microstructure increases as a result of isothermal martensitic transformation. It is suggested that the presence of mechanically-induced hcp phase during aging inhibits the thermally activated nucleation process that leads to the isothermal martensitic transformation.

Probing the isothermal δ→α' martensitic transformation in Pu-Ga with in situ x-ray diffraction

2010 ◽  
Vol 1264 ◽  
Author(s):  
Jason R. Jeffries ◽  
Kerri J.M. Blobaum ◽  
Adam J. Schwartz ◽  
Hyunchae Cynn ◽  
Wenge Yang ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Intermediate Phase ◽  
X Ray Diffraction ◽  
Thermally Induced ◽  
X Ray ◽  
Conditioning Treatment ◽  
Temperature Transformation ◽  
Isothermal Martensitic Transformation ◽  
Photon Source

AbstractThe time-temperature-transformation (TTT) curve for the δ → α′ isothermal martensitic transformation in a Pu-1.9 at. % Ga alloy exhibits an anomalous double-C curve. Recent work suggests that an ambient temperature conditioning treatment enables the lower-C curve. However, the mechanisms responsible for the double-C are still not fully understood. When the δ → α′ transformation is induced by pressure, an intermediate γ′ phase is observed in some alloys. It has been suggested that transformation at upper-C temperatures may proceed via this intermediate phase, while lower-C transformation progresses directly from δ to α′. To investigate the possibility of thermally induced transformation via the intermediate γ′ phase, in situ x-ray diffraction at the Advanced Photon Source was performed. Using transmission x-ray diffraction, the δ → α′ transformation was observed as a function of time and temperature in samples as thin as 30 μm. The intermediate γ′ phase was not observed at -120°C (upper-C curve) or -155 °C (lower-C curve). Results indicate that the bulk of the α′ phase forms relatively rapidly at -120 and -155 °C.

In-situ EBSD study of the degradation behavior in a type 316 Austenitic Stainless Steel during plastic deformation

2021 ◽  
pp. 030932472098493
Author(s):  
Xiao Wang ◽  
Yuetao Zhang ◽  
Huaying Li ◽  
Ming-yu Huang
Keyword(s):  
Plastic Deformation ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Tensile Deformation ◽  
Target Surface ◽  
Local Orientation ◽  
Deformation Degree ◽  
Band Contrast

Type 316 steels have been heavily utilized as the structural material in many construction equipment and infrastructures. This paper reports the characterization of degradation in 316 austenitic stainless steel during the plastic deformation. The in-situ EBSD results revealed that, with the increase of plastic strain, the band contrast (BC) value progressively decreased in both grain and grain boundaries, and the target surface becomes uneven after the plastic tensile, which indicates that the increase of surface roughness. Meanwhile, the KAM and ρGND values are low in the origin specimen but increased significantly after the in-situ tensile. The results indicated that the KAM and ρGND are closely related to the deformation degree of the materials, which can be used as the indicator for assessing the degradation of 316 steel. Besides, the re-orientation of grain occurred after the tensile deformation, which can be recognized from the lattice orientation and local orientation maps.

Experimental study on tensile deformation process of graphitized high carbon steel sheet

2021 ◽  
Vol 4 ◽  
pp. 74-80
Author(s):  
Zhang Yong Jun ◽  
◽  
Li Xin Peng ◽  
Wang Jiu Hua ◽  
Han Jing Tao ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Carbon Steel ◽  
Steel Sheet ◽  
Tensile Deformation ◽  
High Carbon Steel ◽  
Ferrite Matrix ◽  
High Carbon ◽  
Graphite Inclusion ◽  
Carbon Steel Sheet

As the object for the study, graphitized high-carbon steel sheet with a carbon content of 0.66 % was used, the tensile test of this sheet using a universal testing (breaking) machine was performed; as well as in-situ observation of the microstructure in the process of tensile deformation of this sheet using in-situ technology of scanning electron microscopy (SEM) was made. The test results show that the main mechanical properties in different directions of tested graphitized high-carbon steel sheet are relatively the same, that is, for a tensile sample of different directions, the ratio of the yield strength σ0,2 to the tensile strength σв is approximately 0.73; the strain hardening index n is approximately 0.24; the plastic deformation coefficient r is approximately 0.83. This indicates that this sheet did not exhibit significant anisotropy. In the process of tensile, deformation of the specimen is mainly developed from local plastic deformation of the graphite inclusions to the total deformation in the deformation zone of the sample; with the increase of displacement, micro-gap between the graphite inclusion and ferrite grain along the direction of the axis of tensile gradually formed and propagated along the direction perpendicular to the axis of tensile; number of slip lines in the ferrite matrix gradually increased, and the distance between them gradually decreases; when the sample breaks, in the fracture large dimple with the core of graphite inclusion and small dimples in the ferrite appears. And the ferrite matrix near the fracture is covered with slip lines, this shows that the ferritic matrix underwent severe plastic deformation before breaking.

Evolution of texture and internal stresses within polycrystalline rock salt using in situ 3D synchrotron computed tomography and 3D X-ray diffraction

2021 ◽  
Vol 54 (5) ◽  
pp. 1379-1393
Author(s):  
Amirsalar Moslehy ◽  
Khalid A. Alshibli ◽  
Timothy J. Truster ◽  
Peter Kenesei ◽  
Wadi H. Imseeh ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Slip System ◽  
Rock Salt ◽  
Small Scale ◽  
Internal Stresses ◽  
X Ray Diffraction ◽  
Crack Network ◽  
X Ray ◽  
Fully Connected

Rock salt caverns have been extensively used as reliable repositories for hazardous waste such as nuclear waste, oil or compressed gases. Undisturbed rock salt deposits in nature are usually impermeable and have very low porosity. However, rock salt formations under excavation stresses can develop crack networks, which increase their porosities; and in the case of a connected crack network within the media, rock salt may become permeable. Although the relationship between the permeability of rock salt and the applied stresses has been reported in the literature, a microscopic study that investigates the properties influencing this relationship, such as the evolution of texture and internal stresses, has yet to be conducted. This study employs in situ 3D synchrotron micro-computed tomography and 3D X-ray diffraction (3DXRD) on two small-scale polycrystalline rock salt specimens to investigate the evolution of the texture and internal stresses within the specimens. The 3DXRD technique measures the 3D crystal structure and lattice strains within rock salt grains. The specimens were prepared under 1D compression conditions and have shown an initial {111} preferred texture, a dominant {110}〈110〉 slip system and no fully connected crack network. The {111} preferred texture under the unconfined compression experiment became stronger, while the {111}〈110〉 slip system became more prominent. The specimens did not have a fully connected crack network until applied axial stresses reached about 30 MPa, at a point where the impermeability of the material becomes compromised due to the development of multiple major cracks.

scholarly journals Microscale residual stresses in additively manufactured stainless steel

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Wen Chen ◽  
Thomas Voisin ◽  
Yin Zhang ◽  
Jean-Baptiste Florien ◽  
Christopher M. Spadaccini ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Residual Stresses ◽  
Mechanical Behaviour ◽  
Work Hardening ◽  
Computational Modelling ◽  
Internal Stresses ◽  
X Ray Diffraction ◽  
Lattice Strains ◽  
The Impact

Abstract Additively manufactured (AM) metallic materials commonly possess substantial microscale internal stresses that manifest as intergranular and intragranular residual stresses. However, the impact of these residual stresses on the mechanical behaviour of AM materials remains unexplored. Here we combine in situ synchrotron X-ray diffraction experiments and computational modelling to quantify the lattice strains in different families of grains with specific orientations and associated intergranular residual stresses in an AM 316L stainless steel under uniaxial tension. We measure pronounced tension–compression asymmetries in yield strength and work hardening for as-printed stainless steel, and show they are associated with back stresses originating from heterogeneous dislocation distributions and resultant intragranular residual stresses. We further report that heat treatment relieves microscale residual stresses, thereby reducing the tension–compression asymmetries and altering work-hardening behaviour. This work establishes the mechanistic connections between the microscale residual stresses and mechanical behaviour of AM stainless steel.

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