Influence of Carbon Content on the Microstructure and Precipitates of the V-N Microalloyed Steels

2011 ◽  
Vol 335-336 ◽  
pp. 645-649
Author(s):  
Jia Yan Ma ◽  
Xian Zhong Zhang ◽  
Yun Guan ◽  
Zhao Jun Deng
Keyword(s):  
Electron Microscope ◽  
Carbon Content ◽  
Driving Force ◽  
Local Area ◽  
Microalloyed Steels ◽  
Cooling Process ◽  
Intragranular Ferrite ◽  
Transmission Electron ◽  
Ferrite Nucleation ◽  
Strength Effect

The microstructure and precipitates of the V-N microalloyed steels whose carbon content were respectively 0.27% and 0.35%, were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). It is shown that the microstructures of the test steels are all composed of ferrite and pearlite, the area percent of ferrite decreases from 49% to 40% and the grain size also descends from 8.96μm to 8.61μm with the increase of carbon content. TEM results show that the precipitates in two kinds of steels all include a large amount of 10~20nm dispersion distribution irregular flake VC, the part of fibrous VC that grows toward to intragranular ferrite along the grain boundary in the local area, and only a small amount of spherical VN or V (C, N). When the carbon content increases from 0.27% to 0.35%, the number of the spherical VN or V(C,N) increases obviously and the size of it varies from 20~100nm to 45~105nm, while the number of flake VC and fibrous VC decreases significantly and the length of fibrous VC shortens from several micrometers to nanometer size. Experimental results indicate that most of the spherical VN or V (C, N) firstly appear in austenite, then the flake VN and fibrous VN with precipitation strength effect emerge in ferrite during the following γ→α transformation and cooling process. The increase of carbon content can lead to the increase of driving force that VN or V (C, N) firstly appear in austenite, which results in the significant increase of ferrite nucleation rate and the refinement of microstructure.

Nucleation Mechanism of IGF in the HAZs of Ti-Killed HSLA Steel

2014 ◽  
Vol 898 ◽  
pp. 161-163
Author(s):  
Dong Ming Duan ◽  
Meng Xia Tang ◽  
Run Wu ◽  
Yong Bu ◽  
Xiao Chen
Keyword(s):  
Electron Microscope ◽  
Driving Force ◽  
Hsla Steel ◽  
High Strength ◽  
Nucleation Mechanism ◽  
Titanium Oxides ◽  
Lattice Matching ◽  
Transmission Electron ◽  
Thermodynamic Driving Force ◽  
Inert Substrate

The weldability of the steel can be improved by formation of intra-granular ferrite (IGF) in heat affected zones (HAZs) on the edge of weld bead. The nucleation mechanism of IGF of Ti-killed high strength low alloyed (HSLA) steel has already been investigated with the aid of transmission electron microscope. Titanium oxides (Ti2O3) particles with the diameter of 0.4μm and Si-rich complex inclusions (Ti3O5+MnS) with that of 0.5μm can serve as the nuclei of IGF. The nucleation mechanism of IGF is proposed as follows: (1) inclusions are inert substrate. (2) The depletion of the austenite former Mn local to the inclusion increases the thermodynamic driving force of γα for transformation. (3) Lattice matching between inclusion and ferrite reduces the interfacial energy of opposing nucleation.

scholarly journals Detection and Determination of Solute Carbon in Grain Interior to Correlate with the Overall Carbon Content and Grain Size in Ultra-Low-Carbon Steel

2013 ◽  
Vol 19 (S5) ◽  
pp. 66-68 ◽  
Author(s):  
Jiling Dong ◽  
Yinsheng He ◽  
Chan-Gyu Lee ◽  
Byungho Lee ◽  
Jeongbong Yoon ◽  
...  
Keyword(s):  
Grain Size ◽  
Electron Microscope ◽  
Carbon Content ◽  
Three Dimensional ◽  
Low Carbon Steel ◽  
Atom Probe ◽  
Optical Microscope ◽  
Low Carbon ◽  
Transmission Electron ◽  
Solute Carbon

AbstractIn this study, every effort was exerted to determine and accumulate data to correlate microstructural and compositional elements in ultra-low-carbon (ULC) steels to variation of carbon content (12–44 ppm), manganese (0.18–0.36%), and sulfur (0.0066–0.001%). Quantitative analysis of the ULC steel using optical microscope, scanning electron microscope, transmission electron microscope, and three-dimensional atom probe revealed the decrease of grain size and dislocation density with the increase of carbon contents and/or increase of the final delivery temperature. For a given carbon content, the grain interior carbon concentration increases as the grain size increases.

scholarly journals Characterization by Electron Diffraction of Two Thermodynamical Phases of Precipitation in Nb-Microalloyed Steels

2005 ◽  
Vol 480-481 ◽  
pp. 489-494 ◽  
Author(s):  
Manuel Gómez ◽  
S.F. Medina ◽  
Pilar Valles ◽  
Alberto Quispe
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Electron Diffraction Study ◽  
High Strength ◽  
Lattice Parameters ◽  
Microalloyed Steels ◽  
Mean Values ◽  
Transmission Electron ◽  
Analytical System

Excellent mechanical properties (high strength and toughness) of microalloyed steels are mainly caused by induced precipitation during thermomechanical treatment (TMT) and grain refinement. It has been recently found that TMT of Nb-microalloyed steels can give rise to two different kinds of precipitates, manifested by the double plateau in the statically recrystallised fraction (Xa) against time curves. This work presents an electron diffraction study performed in a transmission electron microscope, equipped with an EDS analytical system. Lattice parameters of a great deal of particles, smaller than 200 nm and with face cubic centred structure, have been measured. Frequency distribution of the values of lattice parameters shows that these are grouped in two sets whose mean values are close. Comparison of these values with those found in the literature for carbides, nitrides and carbonitrides usually present in microalloyed steels demonstrates that they are Nb carbonitrides with slight stoichiometric differences (NbCxNy).

scholarly journals Experimental Investigation of the Blanked Surface of C5191 Phosphor Bronze Sheet over a Wide Range of Blanking Speeds

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3335 ◽  
Author(s):  
Lei Wang ◽  
Daochun Hu ◽  
Minghe Chen ◽  
Hongjun Wang
Keyword(s):  
Electron Microscope ◽  
High Speed ◽  
Electron Backscatter Diffraction ◽  
Local Area ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Wide Range ◽  
Backscatter Diffraction

The influence of blanking speed on the blanked surface quality of C5191 bronze phosphorus sheets, with a thickness of 0.12 mm, was systematically studied to demonstrate the mechanism under high speed blanking. The morphology and microstructure of the blanked edge were observed by using a variety of techniques, including optical microscopy (OM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM). The results revealed that the local temperature and microhardness of the shear zone increased with the increase in blanking speed. Moreover, the quality of blanked edge significantly improved with the increase in blanking speed due to the combined influence of strain rate hardening and thermal softening. In addition, the blanked edge grains were elongated along the blanking direction and formed dislocation cells and sub-grains in some areas. The blanked edge is dominated by {000} <100> cubic texture at higher blanking speeds, and {112} <111> texture at lower blanking speeds. When punched at an ultra-high speed of 3000 strokes per minute (SPM 3000), the local area of the blanked edge exhibited distinct microstructural features, including low dislocation density, nanocrystals with high-angle grain boundaries, and significant differences in grain orientation. Additionally, the selected area electron diffraction (SAED) pattern exhibited a discontinuous ring-like structure, indicating the occurrence of adiabatic shearing with dynamic recrystallization.

A Reproducible Selective Stain for Cardiac Sarcoplasmic Reticulum

1974 ◽  
Vol 32 ◽  
pp. 214-215
Author(s):  
R. A. Waugh ◽  
J. R. Sommer
Keyword(s):  
Complex System ◽  
Electron Microscope ◽  
Sarcoplasmic Reticulum ◽  
Transmission Electron Microscope ◽  
Electron Microscopic ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Transmission Electron

Cardiac sarcoplasmic reticulum (SR) is a complex system of intracellular tubules that, due to their small size and juxtaposition to such electron-dense structures as mitochondria and myofibrils, are often inconspicuous in conventionally prepared electron microscopic material. This study reports a method with which the SR is selectively “stained” which facilitates visualizationwith the transmission electron microscope.

Surface Structure of the Spores of Glugea Weissenbergi

1969 ◽  
Vol 27 ◽  
pp. 238-239
Author(s):  
Sanford H. Vernick ◽  
Anastasios Tousimis ◽  
Victor Sprague
Keyword(s):  
Electron Microscope ◽  
Surface Structure ◽  
Transmission Electron Microscope ◽  
Mature Spore ◽  
Spore Surface ◽  
Sectioned Material ◽  
Transmission Electron ◽  
Surface Detail

Recent electron microscope studies have greatly expanded our knowledge of the structure of the Microsporida, particularly of the developing and mature spore. Since these studies involved mainly sectioned material, they have revealed much internal detail of the spores but relatively little surface detail. This report concerns observations on the spore surface by means of the transmission electron microscope.

The High Resolution Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 316-317
Author(s):  
A. V. Crewe
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Vacuum ◽  
Scanning Transmission Electron Microscope ◽  
Ultra High Vacuum ◽  
Resolving Power ◽  
Imaging Characteristics ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Moment

The high resolution STEM is now a fact of life. I think that we have, in the last few years, demonstrated that this instrument is capable of the same resolving power as a CEM but is sufficiently different in its imaging characteristics to offer some real advantages.It seems possible to prove in a quite general way that only a field emission source can give adequate intensity for the highest resolution^ and at the moment this means operating at ultra high vacuum levels. Our experience, however, is that neither the source nor the vacuum are difficult to manage and indeed are simpler than many other systems and substantially trouble-free.

S.E.M.-T.E.M. Image Comparison

1971 ◽  
Vol 29 ◽  
pp. 132-133
Author(s):  
G. M. Greene ◽  
J. W. Sprys
Keyword(s):  
Electron Microscope ◽  
Low Carbon Steel ◽  
Secondary Emission ◽  
Low Carbon ◽  
Preparation Time ◽  
Actual Surface ◽  
Fine Detail ◽  
Transmission Electron ◽  
Transmission Study ◽  
Large Sections

The present study demonstrates that fracture surfaces appear strikingly different when observed in the transmission electron microscope by replication and in the scanning electron microscope by backscattering and secondary emission. It is important to know what form these differences take because of the limitations of each instrument. Replication is useful for study of surfaces too large for insertion into the S.E.M. and for resolution of fine detail at high magnification with the T.E.M. Scanning microscopy reduces sample preparation time and allows large sections of the actual surface to be viewed.In the present investigation various modes of the S.E.M. along with the transmission mode in the T.E.M. were used to study one area of a fatigue surface of a low carbon steel. Following transmission study of a platinum carbon replica in the T.E.M. and S.E.M. the replica was coated with a gold layer approximately 200A° in thickness to improve electron emission.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

Application of Scanning Electron Microscopy to Medical Research

1969 ◽  
Vol 27 ◽  
pp. 12-13
Author(s):  
J. D. Hutchison
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Medical Research ◽  
Prosthetic Heart Valve ◽  
School Of Medicine ◽  
Transmission Electron ◽  
Definition Of ◽  
Mechanism Of Failure ◽  
The Brain ◽  
Scanning Electron

When the transmission electron microscope was commercially introduced a few years ago, it was heralded as one of the most significant aids to medical research of the century. It continues to occupy that niche; however, the scanning electron microscope is gaining rapidly in relative importance as it fills the gap between conventional optical microscopy and transmission electron microscopy.IBM Boulder is conducting three major programs in cooperation with the Colorado School of Medicine. These are the study of the mechanism of failure of the prosthetic heart valve, the study of the ultrastructure of lung tissue, and the definition of the function of the cilia of the ventricular ependyma of the brain.

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