SEGREGATION OF BORON TO GRAIN BOUNDARIES IN IRON AND A STAINLESS STEEL

1975 ◽  
Vol 36 (C4) ◽  
pp. C4-137-C4-140 ◽  
Author(s):  
D. A. MORTIMER
Keyword(s):  
Stainless Steel ◽  
Grain Boundaries

Precipitation formation on ∑5 and ∑7 grain boundaries in 316L stainless steel and their roles on intergranular corrosion

2021 ◽  
pp. 116822
Author(s):  
Shao-Pu Tsai ◽  
Surendra Kumar Makineni ◽  
Baptiste Gault ◽  
Kaori Kawano-Miyata ◽  
Akira Taniyama ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Grain Boundaries ◽  
Intergranular Corrosion ◽  
316L Stainless Steel ◽  
Precipitation Formation

scholarly journals Imaging Hydrogen in Stainless Steel Alloys by Kelvin Probe Force Microscopy

2018 ◽  
Author(s):  
J. D. McNamara ◽  
A. J. Duncan ◽  
M. J. Morgan ◽  
P. S. Korinko
Keyword(s):  
Stainless Steel ◽  
Grain Boundaries ◽  
Contact Potential Difference ◽  
Kelvin Probe Force Microscopy ◽  
Grain Structure ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Steel Alloys ◽  
Force Microscopy ◽  
Net Shaping

Kelvin probe force microscopy (KPFM) was used to image austenitic stainless steel (SS) samples (Type 304L) fabricated by the laser engineered net shaping (LENS®) process. The samples were hydrogen charged (H-charged) and subsequently cut and polished. The surface contact potential difference (CPD) of the samples was measured using the KPFM technique, a form of atomic force microscopy. A set of uncharged samples was also studied for reference and changes in the CPD were on the noise level. For H-charged samples fabricated by the LENS® process, the resulting surface potential images show a change in CPD of about 10 – 20mV around cell-like boundaries (5–10 μm in size) and grain boundaries (50–100 μm in size). The significant change in the CPD is affected by variation of the local work function, which indicates the presence of hydrogen. The elemental composition of the LENS® samples was studied using energy dispersive spectroscopy (EDS) which showed an increase in the atomic percentage of Cr and a decrease in Ni around the cell-like boundaries. The existence of intercellular ferrite on the sub-grain boundaries may explain the propensity of hydrogen to segregate around these regions. The finer grain structure of LENS® samples compared to that of forged or welded samples suggests that the hydrogen can be dispersed differently throughout this material than in traditionally forged austenitic SS. This study is conducted to elucidate the behavior of hydrogen with respect to the microstructure of additively manufactured stainless steel alloys.

Dislocations and stacking faults in stainless steel

1957 ◽  
Vol 240 (1223) ◽  
pp. 524-538 ◽  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stainless Steel ◽  
Grain Boundaries ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Thin Sections ◽  
Partial Dislocations ◽  
Transmission Electron

Further experiments by transmission electron microscopy on thin sections of stainless steel deformed by small amounts have enabled extended dislocations to be observed directly. The arrangement and motion of whole and partial dislocations have been followed in detail. Many of the dislocations are found to have piled up against grain boundaries. Other observations include the formation of wide stacking faults, the interaction of dislocations with twin boundaries, and the formation of dislocations at thin edges of the foils. An estimate is made of the stacking-fault energy from a consideration of the stresses present, and the properties of the dislocations are found to be in agreement with those expected from a metal of low stacking-fault energy.

scholarly journals Investigation on the Corrosion Behavior of Lean Duplex Stainless Steel 2404 after Aging within the 650–850 °C Temperature Range

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 529 ◽  
Author(s):  
Federica Zanotto ◽  
Vincenzo Grassi ◽  
Andrea Balbo ◽  
Fabrizio Zucchi ◽  
Cecilia Monticelli
Keyword(s):  
Stainless Steel ◽  
Grain Boundaries ◽  
Duplex Stainless Steel ◽  
Corrosion Behavior ◽  
Thermal Aging ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Localized Corrosion ◽  
Fast Diffusion ◽  
Lean Duplex Stainless Steel

This paper reports the effects of thermal aging between 650 and 850 °C on the localized corrosion behavior of lean duplex stainless steel (LDSS 2404). Critical pitting temperature (CPT) and double loop electrochemical potentiokinetic reactivation (DL-EPR) tests were performed. The localization of pitting attack and intergranular corrosion (IGC) attack after DL-EPR was investigated by optical (OM) and scanning electron microscopy (SEM) and by focused ion beam (FIB) coupled to SEM. Thermal aging caused the precipitation of mainly chromium nitrides at grain boundaries. Aging at 650 °C or short aging times (5 min) at 750 °C caused nitride precipitation mainly at α/α grain boundaries as a result of fast diffusion of chromium in this phase. Aging at 850 °C or aging times from 10 to 60 min at 750 °C also allowed the precipitation at the α/γ interface. Nitrides at γ/γ grain boundaries were observed rarely and only after long aging times (60 min) at 850 °C. Electrochemical tests showed that in as-received samples, pitting attack only affected the α phase. Conversely, in aged samples, pitting and IGC attack were detected close to nitrides in correspondence of α/α and α/γ grain boundaries depending on aging temperatures and times.

Finite Element Modeling of Selective Laser Melting 316L Stainless Steel Parts for Evaluating the Mechanical Properties

2016 ◽  
Author(s):  
Arman Ahmadi ◽  
Narges Shayesteh Moghaddam ◽  
Mohammad Elahinia ◽  
Haluk E. Karaca ◽  
Reza Mirzaeifar
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Stainless Steel ◽  
Finite Element Model ◽  
Grain Boundaries ◽  
Mechanical Response ◽  
Element Model ◽  
Polycrystalline Materials ◽  
Microstructural Properties ◽  
Laser Melting

Selective laser melting (SLM) is an additive manufacturing technique in which complex parts can be fabricated directly by melting layers of powder from a CAD model. SLM has a wide range of application in biomedicine and other engineering areas and it has a series of advantages over traditional processing techniques. A large number of variables including laser power, scanning speed, scanning line spacing, layer thickness, material based input parameters, etc. have a considerable effect on SLM process materials. The interaction between these parameters is not completely studied. Limited studies on balling effect in SLM, densifications under different processing conditions, and laser re-melting, have been conducted that involved microstructural investigation. Grain boundaries are amongst the most important microstructural properties in polycrystalline materials with a significant effect on the fracture and plastic deformation. In SLM samples, in addition to the grain boundaries, the microstructure has another set of connecting surfaces between the melt pools. In this study, a computational framework is developed to model the mechanical response of SLM processed materials by considering both the grain boundaries and melt pool boundaries in the material. To this end, a 3D finite element model is developed to investigate the effect of various microstructural properties including the grains size, melt pools size, and pool connectivity on the macroscopic mechanical response of the SLM manufactured materials. A conventional microstructural model for studying polycrystalline materials is modified to incorporate the effect of connecting melt pools beside the grain boundaries. In this model, individual melt pools are approximated as overlapped cylinders each containing several grains and grain boundaries, which are modeled to be attached together by the cohesive zone method. This method has been used in modeling adhesives, bonded interfaces, gaskets, and rock fracture. A traction-separation description of the interface is used as the constitutive response of this model. Anisotropic elasticity and crystal plasticity are used as constitutive laws for the material inside the grains. For the experimental verification, stainless steel 316L flat dog bone samples are fabricated by SLM and tested in tension. During fabrication, the power of laser is constant, and the scan speed is changed to study the effect of fabrication parameters on the mechanical properties of the parts and to compare the result with the finite element model.

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