scholarly journals The Effect of Electroslag Remelting on the Microstructure and Mechanical Properties of CrNiMoWMnV Ultrahigh-Strength Steels

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 262
Author(s):  
Mohammed Ali ◽  
David Porter ◽  
Jukka Kömi ◽  
Mamdouh Eissa ◽  
Hoda El Faramawy ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Laser Scanning ◽  
Electron Backscatter Diffraction ◽  
Laser Scanning Confocal Microscopy ◽  
Electroslag Remelting ◽  
Scanning Confocal Microscopy ◽  
Ultrahigh Strength ◽  
Microstructure And Mechanical Properties ◽  
Considerable Impact ◽  
Ultrahigh Strength Steels

The effect of electroslag remelting (ESR) with CaF2-based synthetic slag on the microstructure and mechanical properties of three as-quenched martensitic/martensitic-bainitic ultrahigh-strength steels with tensile strengths in the range of 1250–2000 MPa was investigated. Ingots were produced both without ESR, using induction furnace melting and casting, and with subsequent ESR. The cast ingots were forged at temperatures between 1100 and 950 °C and air cooled. Final microstructures were investigated using laser scanning confocal microscopy, field emission scanning electron microscopy, electron backscatter diffraction, electron probe microanalysis, X-ray diffraction, color etching, and micro-hardness measurements. Mechanical properties were investigated through measurement of hardness, tensile properties and Charpy-V impact toughness. The microstructures of the investigated steels were mainly auto-tempered martensite in addition to small fractions of retained austenite and bainite. Due to the consequences of subtle modifications in chemical composition, ESR had a considerable impact on the final microstructural features: Prior austenite grain, effective martensite grain, and lath sizes were refined by up to 52%, 38%, and 28%, respectively. Moreover, the 95th percentiles in the cumulative size distribution of the precipitates decreased by up to 18%. However, ESR had little, if any, the effect on microsegregation. The variable effects of ESR on mechanical properties and how they depend on the initial steel composition are discussed.

scholarly journals The effect of electroslag remelting on the cleanliness of CrNiMoWMnV ultrahigh-strength steels

2019 ◽  
Vol 55 (3) ◽  
pp. 381-395 ◽  
Author(s):  
M. Ali ◽  
D. Porter ◽  
J. Kömi ◽  
E.P. Heikkinen ◽  
M. Eissa ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Laser Scanning Confocal Microscopy ◽  
Electroslag Remelting ◽  
Chemical Compositions ◽  
Free Energies ◽  
Scanning Confocal Microscopy ◽  
Ultrahigh Strength ◽  
Metallic Inclusions ◽  
Ultrahigh Strength Steels ◽  
Hsc Chemistry

The cleanliness of ultrahigh-strength steels (UHSSs) without and with electroslag remelting (ESR) using a slag with the composition of 70% CaF2, 15% Al2O3, and 15% CaO was studied. Three experimental heats of UHSSs with different chemical compositions were designed, melted in an induction furnace, and refined using ESR. Cast ingots were forged at temperatures between 1100 and 950?C, air cooled, and their non-metallic inclusions (NMIs) were characterized using field emission scanning electron microscopy and laser scanning confocal microscopy. Thermodynamic calculations for the expected NMIs formed in the investigated steels with and without ESR were performed using FactSage 7.2 software while HSC Chemistry version 9.6.1 was used to calculate the standard Gibbs free energies (?G?). As a result of ESR the total impurity levels (TIL% = O% + N% + S%) and NMI contents decreased by as much as 46 % and 62 %, respectively. The NMIs were classified into four major classes: oxides, sulphides, nitrides, and complex multiphase inclusions. ESR brings about large changes in the area percentages, number densities, maximum equivalent circle diameters, and the chemical composition of the various NMIs. Most MnS inclusions were removed although some were re-precipitated on oxide or nitride inclusions leading to multiphase inclusions with an oxide or nitride core surrounded by sulphide, e.g. (MnS.Al2O3) and (MnS. TiN). Also, some sulphides are modified by Ca forming (CaMn)S and CaS.Al2O3. Some nitrides like TiN and (TiV)N are nucleated and precipitated during the solidification phase. Al2O3 inclusions were formed as a result of the addition of Al as a deoxidant to the ESR slag to prevent penetration of oxygen to the molten steel.

Effect of Electroslag Refining on Cleanness, Microstructure and Mechanical Properties of a Newly Developed CrNiMoWMnV Ultrahigh-Strength Steel

2018 ◽  
Vol 786 ◽  
pp. 10-22 ◽  
Author(s):  
Mohammed Ali ◽  
David A. Porter ◽  
Jukka I. Kömi ◽  
Mamdouh Eissa ◽  
Hoda El Faramawy ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Laser Scanning ◽  
Laser Scanning Confocal Microscopy ◽  
Impurity Level ◽  
Scanning Confocal Microscopy ◽  
Ultrahigh Strength ◽  
Ultrahigh Strength Steel ◽  
Microstructure And Mechanical Properties ◽  
Marginal Improvement ◽  
Electroslag Refining

The cleanness, microstructure and mechanical properties of a newly developed CrNiMoWMnV ultrahigh-strength steel with and without electroslag refining (ESR) with 70% CaF2, 15% Al2O3 and 15% CaO have been studied. This steel was designed and melted in an air induction furnace followed by refining using ESR. Cast ingots with and without ESR were forged at temperatures in the range 1100 - 950 °C. Laser scanning confocal microscopy, field emission scanning electron microscopy electron back scattering diffraction, electron probe microanalysis and X-ray diffraction have been used to investigate the microstructure and non-metallic inclusions (NMIs) of forged ingots produced with and without ESR. Hardness, tensile and Charpy-V impact tests were performed. ESR reduced the total impurity level i.e. O%+ N%+ S% by 26 % and the area fractions and numbers of NMIs by 17% and 7% respectively. The NMIs are classified into four major classes: oxides, sulphides, nitrides and complex multiphase inclusions. The microstructure of the forged and air-cooled bars consisted of martensite with a small fraction of distributed retained austenite, a very small fraction of bainite and finely distributed precipitates. The reduction of impurity levels combined with the microstructural changes brought about by the changes in the chemical composition meant that ESR resulted in a significant improvement in some mechanical properties and a marginal improvement in others.

Bendability of Shot Blasted Ultrahigh-Strength Steels

2018 ◽  
Vol 941 ◽  
pp. 510-515
Author(s):  
Antti J. Kaijalainen ◽  
Vili Kesti ◽  
Jouko Heikkala ◽  
Raimo Ruoppa ◽  
David A. Porter ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Laser Scanning ◽  
Rolling Direction ◽  
Laser Scanning Confocal Microscopy ◽  
Shot Blasting ◽  
Scanning Confocal Microscopy ◽  
Ultrahigh Strength ◽  
Axis Parallel ◽  
Ultrahigh Strength Steels ◽  
Normal Scale

The effect of shot blasting on the bendability of two tempered trial ultrahigh-strength steels has been studied by comparing the bending behaviour of otherwise identical plates with and without shot blasting. The yield strength of the studied 10 mm thick trial steel was 700 MPa and 7.5 mm trial steel 1100 MPa. The local microstructures below the different surfaces were characterized using laser scanning confocal microscopy and FESEM. Microhardness profiles and surface roughness (Raand Rz) were measured and bendability was determined using three-point brake press bending. Shot blasting was found to decrease the bendability of both steels. For the 700 MPa steel shot blasting increased the surface roughness metric Rasubstantially from 7.4 μm with the normal scale surface to 12.6 μm, and for the 1100 MPa steel from 2.8 μm to 6.8 μm. For the 700 MPa steel with the bend axis parallel to rolling direction, the minimum usable punch radius for defect-free bends with normal scale surfaces was 13 mm (1.3 x thickness) and for the 1100 MPa steel, 14 mm (1.9 x thickness), while for shot blasted surfaces corresponding values were respectively 20 mm (2.0 x thickness) and 18 mm (2.4 x thickness). All of these values are excellent considering the strength levels involved. Shot blasting increased the subsurface hardness and introduced work hardening of surface layers. Possible explanations for the observed effects of shot blasting on the bendability are discussed.

scholarly journals Characteristics and Kinetics of Bainite Transformation Behaviour in a High-Silicon Medium-Carbon Steel above and below the Ms Temperature

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 539
Author(s):  
Shima Pashangeh ◽  
Seyed Sadegh Ghasemi Banadkouki ◽  
Mahesh Somani ◽  
Jukka Kömi
Keyword(s):  
Laser Scanning ◽  
Electron Backscatter Diffraction ◽  
Isothermal Holding ◽  
Laser Scanning Confocal Microscopy ◽  
Medium Carbon Steel ◽  
Bainitic Transformation ◽  
Transformation Rate ◽  
Transformation Behaviour ◽  
Scanning Confocal Microscopy ◽  
High Silicon

This work deals with the kinetic aspects of bainite formation during isothermal holding above and below the martensite start (Ms~275 °C) temperature using a low-alloy, high-silicon DIN 1.5025 steel in a range suitable for achieving ultrafine/nanostructured bainite. Dilatation measurements were conducted to study transformation behaviour and kinetics, while the microstructural features were examined using laser scanning confocal microscopy and electron backscatter diffraction (EBSD) techniques combined with hardness measurements. The results showed that for isothermal holding above the Ms temperature, the maximum bainitic transformation rate decreased with the decrease in isothermal holding temperature between 450 and 300 °C. On the other hand, for isothermal holding below the Ms temperature at 250 and 200 °C, the maximum rate of transformation was achieved corresponding to region I due to the partitioning of carbon and also possibly because of the ledged growth of isothermal martensite soon after the start of isothermal holding. In addition, a second peak was obvious at about 100 and 500 s, respectively, during holding at 250 and 200 °C due to the occurrence of bainitic transformation, marking the beginning of region II.

scholarly journals Mechanical Properties and Fractographical Analysis by Laser Scanning Confocal Microscopy (LSCM) of Laser Textured Bi(Pb)-2212 Superconducting Materials

2006 ◽  
Vol 47 ◽  
pp. 82-87 ◽  
Author(s):  
F. Capel ◽  
M.A. Madre ◽  
A. Sotelo ◽  
M. Mora ◽  
J.C. Diez ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Confocal Microscopy ◽  
Laser Scanning ◽  
Fracture Process ◽  
Young Modulus ◽  
Laser Scanning Confocal Microscopy ◽  
Zone Melting ◽  
Floating Zone ◽  
Melting Method ◽  
Scanning Confocal Microscopy

Vitreous cylinders with compositions Bi2-xPbxSr2CaCu2Oy, (x = 0 and 0.4) were prepared and used as precursors to fabricate textured bars through a Laser Floating Zone melting method (LFZ). The resulting textured cylindrical bars were annealed and were mechanically characterized through mechanical strength, σ, Young modulus, E, Vickers hardness, H, and Weibull parameters, S0 and m. The study of the mechanisms controlling the fracture process was made by means of the fractographical analysis using Laser Scanning Confocal Microscopy (LSCM). Finally, the microstructure was determined and correlated with the mechanical properties.

Correlating Nanoparticle Dispersion to Surface Mechanical Properties of TiO2/Polymer Composites

2009 ◽  
Vol 1224 ◽  
Author(s):  
Yongyan Pang ◽  
Stephanie S. Watson ◽  
Aaron M. Forster ◽  
Lipiin Sung
Keyword(s):  
Mechanical Properties ◽  
Laser Scanning ◽  
Laser Scanning Confocal Microscopy ◽  
Nanoparticle Dispersion ◽  
Depth Sensing ◽  
Near Surface ◽  
Scanning Confocal Microscopy ◽  
Latex Coatings ◽  
Nanoparticle Clusters ◽  
Better Than

AbstractThe objective of this study is to characterize the nanoparticle dispersion and to investigate its effect on the surface mechanical properties of nanoparticle-polymer systems. Two types of TiO2 nanoparticles were chosen to mix in two polymeric matrices: solvent-borne acrylic urethane (AU) and water-borne butyl-acrylic styrene latex (latex) coatings. Nanoparticle dispersion was characterized using laser scanning confocal microscopy. Overall, Particle A (PA, without surface treatment) dispersed better than Particle B (PB, organic treatment) in both systems. The AU-PA system exhibited the best dispersion of the four systems, however PB forms big clusters in both of the matrices. Surface mechanical properties, such as surface modulus at micron and sub-micron length scales were determined from depth sensing indentation equipped with a pyramidal tip or a conical tip. The surface mechanical properties were strongly affected by the dispersion of nanoparticle clusters, and a good correlation was found between dispersion of nanoparticle clusters near surface and the modulus-depth mapping using a pyramid tip.

Laser Scanning Confocal Microscopy and Three-Dimesnsional Reconstruction of the Mitotic Spindles of Unequally Dividing Embryonic Cells

1990 ◽  
Vol 48 (3) ◽  
pp. 166-167
Author(s):  
J. Holy ◽  
G. Schatten
Keyword(s):  
Confocal Microscopy ◽  
Mitotic Spindle ◽  
Laser Scanning ◽  
Three Dimensional ◽  
Laser Scanning Confocal Microscopy ◽  
Two Dimensions ◽  
Embryonic Cells ◽  
Mitotic Spindles ◽  
Cleavage Division ◽  
Scanning Confocal Microscopy

One of the classic limitations of light microscopy has been the fact that three dimensional biological events could only be visualized in two dimensions. Recently, this shortcoming has been overcome by combining the technologies of laser scanning confocal microscopy (LSCM) and computer processing of microscopical data by volume rendering methods. We have employed these techniques to examine morphogenetic events characterizing early development of sea urchin embryos. Specifically, the fourth cleavage division was examined because it is at this point that the first morphological signs of cell differentiation appear, manifested in the production of macromeres and micromeres by unequally dividing vegetal blastomeres.The mitotic spindle within vegetal blastomeres undergoing unequal cleavage are highly polarized and develop specialized, flattened asters toward the micromere pole. In order to reconstruct the three-dimensional features of these spindles, both isolated spindles and intact, extracted embryos were fluorescently labeled with antibodies directed against either centrosomes or tubulin.

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