scholarly journals Effect of Tempering Treatment on Microstructural Evolution and Mechanical Behavior of Heavy-Wall Heat Induction Seamless Bend Pipe

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 259
Author(s):  
Juntai Hu ◽  
Yu Liu ◽  
Ge Wang ◽  
Qiang Li ◽  
Jianyang Wen ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Dislocation Density ◽  
Uniform Elongation ◽  
Cell Structure ◽  
Optical Microscope ◽  
Dislocation Cell ◽  
Granular Bainite ◽  
Tempering Temperature ◽  
Bend Pipe ◽  
Tempering Treatment

In this paper, the microstructure and mechanical properties of heavy-wall seamless bend pipe after quenching at different tempering temperatures, including 550 °C, 600 °C, 650 °C, and 700 °C, were studied. Microstructure and dislocations observations were characterized by means of an optical microscope, a scanning electron microscope, a transmission electron microscope, and X-ray diffraction. As the tempering temperature increases, the dislocation density in the test steel gradually decreases, and the precipitation behavior of (Nb, V)(C, N) increases. The sample tempered at 650 °C exhibits a granular bainite structure with a dislocation cell structure and a large number of smaller precipitates. The yield platforms of tempered samples at 650 °C and 700 °C are attributed to the pinning effect of the Cottrell atmosphere on dislocations. The sample tempered at 650 °C not only presents the highest strength, but also the highest uniform elongation, which is attributed to the higher strain-hardening rate and instantaneous work-hardening index. This is closely related to the multiplication of dislocations, the interaction between dislocations and dislocations, and the interaction between dislocations and precipitates during plastic deformation of the 650 °C-tempered samples with low dislocation density, which delays the occurrence of necking.

Laser Irradiation of Nickel: Defect Structures and Surface Alloying

1980 ◽  
Vol 1 ◽  
Author(s):  
L. Buene ◽  
D.C. Jacobson ◽  
S. Nakahara ◽  
J.M. Poate ◽  
C.W. Draper ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Dislocation Density ◽  
Single Crystals ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Dislocation Network ◽  
Defect Structures ◽  
Surface Alloying ◽  
Surface Layers ◽  
Laser Melting

ABSTRACTSurface layers of Ni crystals have been melted with Q-switched Nd-YAG laser radiation. The epitaxially regrown surface layers show significant differences between 〈100〉 and 〈111〉 crystals cut from the same boule. The 〈100〉 crystals exhibit a dislocation cell structure with a dislocation density of l011 - 1012 cm-2. The 〈111〉 crystals contain a laterally uniform dislocation network resulting in a much higher dislocation density for the 〈111〉 surface. The elements Ag, Au, Pd, Sn and Ta have been implanted into Ni single crystals at surface concentrations of up to 20 at %. All the as- implanted systems demonstrate solid solubility. We have used these implanted systems to study the alloys formed by laser melting of Ni. In all systems, with the exception of Ag, 100% of the atoms are trapped on lattice sites.

The Ultra-Fine Bainitic Steels and Refinement Technology

2007 ◽  
Vol 539-543 ◽  
pp. 4566-4571
Author(s):  
Xue Min Wang ◽  
Xin Lai He ◽  
Shan Wu Yang ◽  
Cheng Jia Shang
Keyword(s):  
Electron Microscope ◽  
Acicular Ferrite ◽  
Large Scale ◽  
Optical Microscope ◽  
Dislocation Cell ◽  
Scale Production ◽  
Bainite Transformation ◽  
Dislocation Configuration ◽  
Bainitic Steels ◽  
Refinement Mechanism

By employing the new developed relaxation-precipitation-controlling phase transformation (RPC) technique in large scale production the bainitic steels with ultra fine bainite has been obtained. These bainitic steels have good synergistic properties. With the aid of thermal simulation the refinement mechanism of RPC technique has also been investigated. The optical microscope, scanning electron microscope, transmission electron microscope and Electron back scattering diffraction technique were employed to study the features of microstructure produced by RPC technique, precipitation and the evolution of dislocation configuration during the relaxation. The results show that when produced by RPC technique the microstructure of the steel is mainly ultra-fine lath bainite packets, and these bainite packets block each other. It is also found that during the relaxation the dislocation cells form and strain induced precipitation occurs, the dislocation cell pinned by the precipitates can confine the bainite transformation. After the relaxation during the cooling the acicular ferrite forms at first and in succeeding the bainite transformation is blocked by the acicular ferrite and the bainite is refined effectively.

A Fretting Damage Analysis of Railway Axle

2013 ◽  
Vol 652-654 ◽  
pp. 1393-1398 ◽  
Author(s):  
Yue Jun Zhang ◽  
Jin Fang Peng ◽  
Zhen Bing Cai ◽  
Min Hao Zhu
Keyword(s):  
Electron Microscope ◽  
Dislocation Density ◽  
Cellular Structure ◽  
Optical Microscope ◽  
Hardness Tester ◽  
Press Fit ◽  
Railway Axle ◽  
Transmission Electron ◽  
Leeb Hardness ◽  
Fretting Damage

A railway axle operated over 6×105 km has been detected by varied micro-examination methods in detail. The examination of Leeb hardness tester results showed that the hardness of the press-fit seats presented higher hardness than that of other sites. According to the micro morphological analyses by optical microscope (OM), scanning electron microscope (SEM), energy dispersive X-ray spectrum (EDX), and profilometer on the surface at different press-fit seats, the most severe damage band was occurred at the inner edge of wheel seat near the gear seat. The transmission electron microscope (TEM) results indicated that the dislocation density of subsurface, beneath the axle surface about 20 μm, was much higher with a great deal of dislocation tangles, pile-ups and cellular structure formation. However, when the examination depth increased to 100 μm, no cellular structure can be founded, the dislocation density was very low, so the damage depth was less than 100 μm.

Effect of Interpass Temperature on Microstructure and Mechanical Properties of Weld Metal of 690 MPa HSLA Steel

2012 ◽  
Vol 706-709 ◽  
pp. 2246-2252 ◽  
Author(s):  
Yun Peng ◽  
Ai Hua Wang ◽  
Hong Jun Xiao ◽  
Zhi Ling Tian
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Weld Metal ◽  
Hsla Steel ◽  
Plate Thickness ◽  
Optical Microscope ◽  
Granular Bainite ◽  
Mechanical Equipment ◽  
Microstructure And Mechanical Properties ◽  
Interpass Temperature

690 MPa grade HSLA steel has wide application in engineering, such as mechanical equipment and oceanographic platform. Qualified joint is crucial for structure safety. Many factors, such as preheating temperature and interpass temperature, welding heat input and plate thickness, may influence the welding thermal cycle so that microstructure and mechanical properties of weld metal are changed. In this paper, the effect of interpass temperature on microstructure and mechanical properties of weld metal of 690 MPa grade steel are studied. Gas metal arc welding method was used to weld the joint. Four interpass temperatures, 80°C, 120°C, 160°C and 200°C are adopted during welding. Optical microscope, scanning electron microscope, transmission electron microscope and electron back-scattered diffraction (EBSD) were used to analyze the microstructure of weld metal. Tensile test and impact test were used to measure its mechanical properties. Research results show that the weld metal are composed of lath bainite and granular bainite. M-A constituents are found on grain boundary and inside grains. The shape and size of bainite structure and M-A constituent are detailed. The distribution and quantity of residual austenite are also detected. The relationship between microstructure and mechanical properties is discussed. Experiment results show that when interpass temperature is 80°C the yield strength and impact toughness are higher than the other three cases.

X-ray determination of dislocation density and arrangement in plastically deformed copper

2000 ◽  
Vol 33 (5) ◽  
pp. 1284-1294 ◽  
Author(s):  
D. Breuer ◽  
P. Klimanek ◽  
W. Pantleon
Keyword(s):  
Dislocation Density ◽  
Profile Analysis ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Double Crystal ◽  
Mean Values ◽  
X Ray ◽  
Dislocation Cell Structure ◽  
X Ray Scattering

Using the kinematical theory of X-ray scattering by crystals with dislocations as developed by Krivoglazet al.and Wilkens, the dislocation content of compressed copper single and polycrystals was investigated by means of profile analysis of selected diffraction peaks. Measurements of radial intensity distributionsI(2θ) were performed with a double-crystal spectrometer in the case of the single crystals and with conventional polycrystal diffractometers in the case of the polycrystals. Additionally, the misorientations Θ occurring within the dislocation cell structure because of the accumulation of excess dislocations of one sign were investigated by means of rocking curves of the single-crystal reflections and by evaluation of electron backscattering patterns (EBSPs). Within a wide deformation range, the mean total dislocation density ρdcan be related well to the flow stressviathe Taylor relationship. Assuming a random distribution of the misorientations Θ between adjacent dislocation cells, the evaluation of the rocking curves gives mean values 〈|Θ|〉 much smaller than those determined by EBSP analysis. For this reason, a model of a dislocation cell structure with restrictedly correlated misorientations, which leads to better agreement of the X-ray and the EBSP data, is proposed.

Asymmetric X-ray line broadening of plastically deformed crystals. II. Evaluation procedure and application to [001]-Cu crystals

1989 ◽  
Vol 22 (1) ◽  
pp. 26-34 ◽  
Author(s):  
T. Ungár ◽  
I. Groma ◽  
M. Wilkens
Keyword(s):  
Dislocation Density ◽  
Dislocation Structure ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Line Profiles ◽  
Line Broadening ◽  
Spatial Fluctuation ◽  
X Ray ◽  
Dislocation Cell Structure ◽  
Dipole Polarization

In paper I [Groma, Ungár & Wilkens (1988). J. Appl. Cryst. 21, 47–53] a theory was developed to interpret the asymmetric X-ray line broadening of plastically deformed crystals. It was shown that the dislocation structure can be described by five distinct parameters, namely the dislocation density, the mean quadratic spatial fluctuation of the dislocation density, the effective outer cut-off radius, the dipole polarization and the spatial fluctuation of the dipole polarization of the dislocation structure. In this paper a procedure is developed to evaluate these parameters from the Fourier transform of the line profiles. The theory and this procedure are tested by applying it to the asymmetric line profiles of tensile-deformed Cu single crystals orientated for ideal multiple slip. The asymmetry of these profiles is assigned to the dipole polarization of the dislocation cell structure and is directly correlated to residual long-range internal stresses. It is shown that the data can be interpreted in terms of the quasi-composite model of the dislocation cell structure developed earlier for the same material.

Bake Precipitation Behavior in AA5182 Sheet for Can End Stock

2018 ◽  
Vol 913 ◽  
pp. 37-42
Author(s):  
Yang Yang ◽  
Pi Zhi Zhao ◽  
Li Ying Zou ◽  
Rong Hui Fan
Keyword(s):  
Electron Microscope ◽  
Dislocation Density ◽  
Shear Bands ◽  
Optical Microscope ◽  
X Ray Diffraction ◽  
Precipitation Behavior ◽  
X Ray ◽  
Hardness Tester ◽  
Softening Curve ◽  
Scanning Electron

By means of Vickers hardness tester, optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and high resolution transmitted electron microscope (HRTEM), the bake softening and precipitation behaviors of AA5182 H19 sheet for can end stock at 205°C and 249°C were investigated. All specimens at both temperatures showed recovery and bake softening phenomenon, which meaning the dislocation density and HV decreased. However, the specimens baked at 205°C showed higher recovery impediment, because the bake softening curve departed from the dynamic laws when it had less amount of recovery than the specimens baked at 249°C. The hardness was higher for the specimen baked at 205°C compared with the specimen baked at 249°C, even both specimens had the same dislocation density measured by XRD. Further observations revealed that the precipitated particles in the specimens baked at 205°C distributed along the shear bands. The precipitates were needle shape with the length of 5-15 nm and the width of 5-10 atom layers, which occurred mostly in the area with higher dislocation density. These precipitates were guessed to be Al-Mg binary phases, which could contribute to the higher hardness of the specimens baked at 205°C.

Effects of Two-Step Tempering Treatment on the Microstructural Formation of T91 Ferritic Steels

2011 ◽  
Vol 172-174 ◽  
pp. 875-880 ◽  
Author(s):  
Chen Xi Liu ◽  
Ze Sheng Yan ◽  
Zhi Zhong Dong ◽  
Yong Chang Liu ◽  
Bao Qun Ning
Keyword(s):  
High Temperature ◽  
Dislocation Density ◽  
Power Plants ◽  
Mechanical Performance ◽  
Service Condition ◽  
Tempering Temperature ◽  
Tempering Treatment ◽  
Main Steam ◽  
Martensitic Lath ◽  
Tempering Process

As a representative type of high Cr ferritic heat-resistant steels, T91 steels (ASME SA-213 T91/P91) has been recognized as the preferable materials and widely used in high-temperature structural components such as header and main steam pipe in advanced power plants. For the service condition is tempered martensites, its corresponding microstructure and mechanical performance are mainly adjusted by the tempering treatment. After exploring the size and number of MX and M23C6precipitating particles and the width of martensitic lath as a function of tempering temperature, it is recognized that the high tempering temperature leads to an increase of secondary hardening effect, while the low tempering temperature brings a high dislocation density and a small martensitic lath. Hence, a two-step tempering treatment was developed after the traditional normalizing process, in which the T91 steels sample was firstly tempered at a low temperature in order to form some precipitates and then tempered at a high temperature. Those firstly-formed precipitates would pin the dislocations and martensitic laths on the subsequent tempering process, which finally leads to more precipitates, higher dislocation density and smaller martensitic lath width than that obtained from the traditional tempering process.

TEM study on fine carbide precipitates and dislocation cell structure

1990 ◽  
Vol 48 (4) ◽  
pp. 904-905
Author(s):  
Mengzhe Chen ◽  
Siqin Wang ◽  
Jun Ke
Keyword(s):  
Carbide Particle ◽  
Cell Structure ◽  
Ferrite Matrix ◽  
Dislocation Cell ◽  
Isothermal Treatment ◽  
Particle Sizes ◽  
Dislocation Cell Structure ◽  
Thin Foils ◽  
Hsla Steels ◽  
Fine Carbide

A series of investigations have been conducted into the nature and origin of the dislocation cell structure. R.J.Klassen calculated that the dislocation cell limiting size in pure ferrite matrix is about 0.4 μm. M.N.Bassion estimated the size of dislocation cell in deformed ferrite of HSLA steels to be of the same order.In this paper, TEM observation has been concentrated on the interaction of fine carbide precipitates with dislocation cell structure in deformed Fe-C-V (0.05%C, 0.13% and 0.57%V) and Fe-C-Nb (0.07 %C and 0.04%Nb) alloys and compared with that in Fe-C (0.05%). Specimens were austenitized at 1500 “C/20 min and followed by isothermal treatment at 750 °C and 800 “C for 20, 40 and 120 minutes . The carbide particle sizes in these steels are from 9 to 86nm measured from carbon extraction replicas. Specimens for TEM were cut from differently deformed areas of tensile specimens deformed at room temperture. The thin foils were jet electropolished at -20 C in a solution of 10% perchloric acid and 90% ethanol. The TEM observation was carried out in JEM 100CX , EM420 at 100kv and JEM 2000FX at 200kv.

New form of Transmission Cross Coefficient for High-Resolution Imaging

1990 ◽  
Vol 48 (1) ◽  
pp. 60-61
Author(s):  
Kazuo Ishizuka
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Transmission Function ◽  
Incident Beam ◽  
Optical Microscope ◽  
Strong Interactions ◽  
Small Range ◽  
Specimen Thickness ◽  
Beam Direction ◽  
Diffracted Waves

It is well known that taking into account spacial and temporal coherency of illumination as well as the wave aberration is important to interpret an image of a high-resolution electron microscope (HREM). This occues, because coherency of incident electrons restricts transmission of image information. Due to its large spherical and chromatic aberrations, the electron microscope requires higher coherency than the optical microscope. On an application of HREM for a strong scattering object, we have to estimate the contribution of the interference between the diffracted waves on an image formation. The contribution of each pair of diffracted waves may be properly represented by the transmission cross coefficients (TCC) between these waves. In this report, we will show an improved form of the TCC including second order derivatives, and compare it with the first order TCC.In the electron microscope the specimen is illuminated by quasi monochromatic electrons having a small range of illumination directions. Thus, the image intensity for each energy and each incident direction should be summed to give an intensity to be observed. However, this is a time consuming process, if the ranges of incident energy and/or illumination direction are large. To avoid this difficulty, we can use the TCC by assuming that a transmission function of the specimen does not depend on the incident beam direction. This is not always true, because dynamical scattering is important owing to strong interactions of electrons with the specimen. However, in the case of HREM, both the specimen thickness and the illumination angle should be small. Therefore we may neglect the dependency of the transmission function on the incident beam direction.

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