scholarly journals The Evolution of Complex Carbide Precipitates in a Low Alloy Cr–Mo–V Steel after Long-Term Aging Treatment

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1724 ◽  
Author(s):  
Zili Liu ◽  
Chunming Liu ◽  
Lede Miao ◽  
Xiaofei Guo ◽  
Jianhua Ding ◽  
...  
Keyword(s):  
Aging Treatment ◽  
Nucleation Site ◽  
Secondary Phases ◽  
Orientation Relationships ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
The Matrix ◽  
Complex Carbide

Complex carbide precipitates in a quenched and tempered low alloy Cr–Mo–V steel after long-term aging at 650 °C for 13,000 h and 30,000 h were investigated in this study. The mass fraction and sizes of precipitates were quantified by electrolytical extraction technique. The types of precipitate were further studied by combined X-ray diffraction and transmission electron microscopy with selected area electron diffraction and energy dispersive spectrometry. A series of carbide precipitates, namely MC, M7C3, M6C, and M2C, were found existing in the near-equilibrium state. The precipitate sequence of these carbides was identified as MC + M7C3 + M2C → MC + M2C + M7C3 + M6C → MC + M7C3 + M6C. It was clarified that the stable phases for the investigated steel aged at 650 °C were composed of MC, M7C3, and M6C. For the first time, the in-situ transformations of M2C to M6C and M7C3 to M6C were directly observed. It was also observed that the nucleation site of the M6C was located at the interface of M7C3 carbides and the matrix. The orientation relationships between the secondary phases of the in-situ transforming carbides aged for 13,000 h and 30,000 h at 650 °C were established. The coherent interfaces between these secondary phases became incoherent with prolonged aging treatment due to the exerted strain field of the growing carbides.

Nanoscale Sn Inclusions in Al – Structure and Melting-Solidification Properties

1999 ◽  
Vol 580 ◽  
Author(s):  
E. Johnson ◽  
C.R.H. Bahl ◽  
V.S. Touboltsev ◽  
A. Johansen
Keyword(s):  
Size Dependence ◽  
Rutherford Backscattering Spectrometry ◽  
Lattice Parameters ◽  
Orientation Relationships ◽  
Size Dependent ◽  
Transmission Electron ◽  
The Matrix ◽  
Al Matrix ◽  
Melting And Solidification

AbstractAl-Sn surface alloys with 2-3 at.% Sn have been made by ion implantation of Sn in Al. The microstructure of the alloys consists of dense distributions of nanoscale Sn inclusions embedded in the Al matrix. For implantations carried out at 425 K the inclusions have sizes in the range from about 2 to 15 nm. The structure of the inclusions is tetragonal - the white Sn structure – with lattice parameters of a = 0.583 nm and c = 0.318 nm respectively, i.e. identical to the lattice parameters of bulk Sn. The inclusions grow in preferred alignment with the matrix and the most commonly observed orientation relationships is given by (100)Sn ||(111)Al and [010]Sn || [211]Al. The shape of the inclusions is partly faceted and partly rounded with larger flat facets on the {100}Sn/{111}Al interfaces. Melting and solidification of the inclusions, which have been studied by in-situ transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) in combination with channeling, shows a distinct hysteresis. Melting of the inclusions which is associated with a distinct premelting, takes place in the range from about 430 K to 485 K, i.e. significantly below the bulk melting point of 505 K. The premelting is size dependent and the smallest inclusions melt at the lowest temperatures. Solidification requires a substantial undercooling and takes place from around 400 K with a much weaker size dependence.

In situ TEM observations of melting in nanosized eutectic Pb-Cd inclusions embedded in Al

1996 ◽  
Vol 54 ◽  
pp. 986-987
Author(s):  
S. Hagège ◽  
U. Dahmen ◽  
E. Johnson ◽  
A. Johansen ◽  
V.S. Tuboltsev
Keyword(s):  
Electron Microscope ◽  
Melt Spinning ◽  
Ternary Alloys ◽  
Solid Matrix ◽  
Eutectic System ◽  
In Situ Tem ◽  
In Situ Observation ◽  
Orientation Relationships ◽  
Transmission Electron

Small particles of a low-melting phase embedded in a solid matrix with a higher melting point offer the possibility of studying the mechanisms of melting and solidification directly by in-situ observation in a transmission electron microscope. Previous studies of Pb, Cd and other low-melting inclusions embedded in an Al matrix have shown well-defined orientation relationships, strongly faceted shapes, and an unusual size-dependent superheating before melting.[e.g. 1,2].In the present study we have examined the shapes and thermal behavior of eutectic Pb-Cd inclusions in Al. Pb and Cd form a simple eutectic system with each other, but both elements are insoluble in solid Al. Ternary alloys of Al (Pb,Cd) were prepared from high purity elements by melt spinning or by sequential ion implantation of the two alloying additions to achieve a total alloying addition of up to lat%. TEM observations were made using a heating stage in a 200kV electron microscope equipped with a video system for recording dynamic behavior.

scholarly journals Microstructure and properties of nano-laminated Y3Si2C2 ceramics fabricated via in situ reaction by spark plasma sintering

2021 ◽  
Vol 10 (3) ◽  
pp. 578-586
Author(s):  
Lin-Kun Shi ◽  
Xiaobing Zhou ◽  
Jian-Qing Dai ◽  
Ke Chen ◽  
Zhengren Huang ◽  
...  
Keyword(s):  
Spark Plasma Sintering ◽  
Atomic Scale ◽  
Max Phase ◽  
X Ray Diffraction ◽  
Selected Area Electron Diffraction ◽  
Plasma Sintering ◽  
Transmission Electron ◽  
Spark Plasma ◽  
Diffraction Patterns

AbstractA nano-laminated Y3Si2C2 ceramic material was successfully synthesized via an in situ reaction between YH2 and SiC using spark plasma sintering technology. A MAX phase-like ternary layered structure of Y3Si2C2 was observed at the atomic-scale by high resolution transmission electron microscopy. The lattice parameters calculated from both X-ray diffraction and selected area electron diffraction patterns are in good agreement with the reported theoretical results. The nano-laminated fracture of kink boundaries, delamination, and slipping were observed at the tip of the Vickers indents. The elastic modulus and Vickers hardness of Y3Si2C2 ceramics (with 5.5 wt% Y2O3) sintered at 1500 °C were 156 and 6.4 GPa, respectively. The corresponding values of thermal and electrical conductivity were 13.7 W·m-1·K-1 and 6.3×105 S·m-1, respectively.

The Investigation on Aluminium Alloys Automobile Wheel with Low-Titanium Content Produced by Electrolysis

2005 ◽  
Vol 475-479 ◽  
pp. 317-320 ◽  
Author(s):  
Jing Pei Xie ◽  
Ji Wen Li ◽  
Zhong Xia Liu ◽  
Ai Qin Wang ◽  
Yong Gang Weng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Aluminium Alloys ◽  
Solution Treatment ◽  
A356 Alloy ◽  
Aging Treatment ◽  
Titanium Content ◽  
The Matrix ◽  
Automobile Wheel

The in-situ Ti alloying of aluminium alloys was fulfilled by electrolysis, and the material was made into A356 alloy and used in automobile wheels. The results show that the grains of the A356 alloy was refined and the second dendrites arm was shortened due to the in-situ Ti alloying. Trough 3-hour solution treatment and 2-hour aging treatment for the A356 alloy, the microstructures were homogeneous, and Si particles were spheroid and distribute in the matrix fully. The outstanding mechanical properties with tensile strength (σb≥300Mpa) and elongation values (δ≥10%) have been obtained because the heat treatment was optimized. Compared with the traditional materials, tensile strength and elongation were increased by 7.6~14.1% and 7.4~44.3% respectively. The qualities of the automobile wheels were improved remarkably.

scholarly journals High-Resolution Microstructure Characterization of Additively Manufactured X5CrNiCuNb17-4 Maraging Steel during Ex and in Situ Thermal Treatment

2021 ◽  
Author(s):  
Mihaela Albu ◽  
Bernd Panzirsch ◽  
Hartmuth Schröttner ◽  
Stefan Mitsche ◽  
Klaus Reichmann ◽  
...  
Keyword(s):  
Maraging Steel ◽  
Elevated Temperatures ◽  
Scanning Transmission Electron Microscope ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Matrix ◽  
Powder Particles ◽  
In Situ Heating ◽  
Heating Up

Powder and SLM additively manufactured parts of X5CrNiCuNb17-4 maraging steel were systematically investigated by electron microscopy to understand the relationship between the properties of the powder grains and the microstructure of the printed parts. We prove that satellites, irregularities and superficial oxidation of powder particles can be transformed into an advantage through the formation of nanoscale (AlMnSiTiCr)-oxides in the matrix during the printing process. The nano-oxides showed extensive stability in terms of size, spherical morphology, chemical composition and crystallographic disorder upon in situ heating up to 950°C in the scanning transmission electron microscope. Their presence thus indicates a potential for oxide-dispersive strengthening of this steel, which may be beneficial for creep resistance at elevated temperatures. The nucleation of copper clusters and their evolution into nanoparticles as well as the precipitation of Ni and Cr particles upon in situ heating have as well been systematically documented.

Microstructural Characterization, Mechanical Properties and Wear Resistance of TiCP Reinforced Ni-Alloy Coatings by Laser Synthesis

2000 ◽  
Author(s):  
D. L. Tu ◽  
A. Kar ◽  
X. L. Wu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Wear Resistance ◽  
Chemical Reaction ◽  
Phase Interface ◽  
High Fracture Toughness ◽  
Transmission Electron ◽  
Ni Alloy ◽  
The Matrix

Abstract Titanium carbide particle (TiCp)-reinforced Ni alloy composite coatings are synthesized by laser cladding using a cw 3 kW CO2 laser. Two kinds of coatings are possible in terms of the origin of TiCp: undissolved TiCp and in-situ generated TiCp. The former originates from the TiCp pre-coated on the sample whereas the latter from in-situ chemical reaction between titanium and graphite in the molten pool during laser irradiation. For the coating reinforced by TiCp formed in-situ, the sub-micron TiCp particles are formed and uniformly distributed because of the in-situ reaction and trapping effect during rapid solidification. Graded distribution of TiCp is obtained on a macro scale. The volume fraction increases from 1.86% at the coating-substrate interface to 38.4% at the coating surface. For the coating reinforced by undissolved TiCp, analytical transmission electron microscopy (ATEM) and high resolution transmission electron microscopy (HRTEM) observations show the existence of the epitaxial growth of TiC, the precipitation of CrB and M23C6, and the chemical reaction between Ti and B elements around phase interfaces of undissolved TiCp. In the matrix near the phase interface of undissolved TiCp, the loading curve obtained by nanoindenter exhibits pop-in phenomena due to the plastic deformation of cracks or debonding of TiCp from the matrix. For TiCp generated in-situ, no pop-in mark appears, indicating high fracture toughness. Coating with TiCp generated in-situ exhibits higher hardness and modulus than the coating with undissolved TiCp at regions near the phase interface. The coating reinforced by TiCp generated in-situ also displays higher impact wear resistance and abrasive wear resistance compared to the coatings with undissolved TiCp and without TiCp respectively.

Growth and Characterization of Cobalt-filled Carbon Nanotubes Prepared by a Simple Catalytic Method

2003 ◽  
Vol 776 ◽  
Author(s):  
Xicheng Ma ◽  
Yuanhua Cai ◽  
Xia Li ◽  
Ning Lun ◽  
Shulin Wen
Keyword(s):  
Carbon Nanotubes ◽  
Metallic Nanoparticles ◽  
Low Cost ◽  
Catalytic Method ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
One Step

AbstractHigh-quality cobalt-filled carbon nanotubes (CNTs) were prepared in situ in the decomposition of benzene over Co/silica-gel nano-scale catalysts. Unlike the previous reports, the catalysts needn't be pre-reduced prior to the forming of Co-filled CNTs, thus the advantage of this method is that Co-filled CNTs can be produced in one step, at a relatively low cost. Transmission electron microscopy (TEM) investigation showed that the products contained abundance of CNTs and most of them were filled with metallic nanoparticles or nanorods. High-resolution TEM (HRTEM), selected area electron diffraction (SAED) patterns and energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Co inside the nanotubes. The encapsulated Co was further identified always as high temperature alpha-Co phase with fcc structure, which frequently consists of twinned boundaries and stacking faults. Based on the experimental results, a possible growth mechanism of the Co-filled CNTs was proposed.

scholarly journals Study of the Microstructure and Crack Evolution Behavior of Al-5Fe-1.5Er Alloy

Materials ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 172 ◽  
Author(s):  
Ming Li ◽  
Zhiming Shi ◽  
Xiufeng Wu ◽  
Huhe Wang ◽  
Yubao Liu
Keyword(s):  
Electron Microscopy ◽  
Crack Initiation ◽  
Tensile Tests ◽  
Eutectic Structure ◽  
Interface Structure ◽  
X Ray ◽  
Transmission Electron ◽  
The Matrix ◽  
Evolution Behavior

In this work, the microstructure of Al-5Fe-1.5Er alloy was characterized and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) techniques. The effect of microstructure on the behavior of crack initiation and propagation was investigated using in situ tensile testing. The results showed that when 1.5 wt.% Er was added in the Al-5Fe alloy, the microstructure consisted of α-Al matrix, Al3Fe, Al4Er, and Al3Fe + Al4Er eutectic phases. The twin structure of Al3Fe phase was observed, and the twin plane was {001}. Moreover, a continuous concave and convex interface structure of Al4Er was observed. Furthermore, Al3Fe was in the form of a sheet with a clear gap inside. In situ tensile tests of the alloy at room temperature showed that the crack initiation mainly occurred in the Al3Fe phase, and that the crack propagation modes included intergranular and trans-granular expansions. The crack trans-granular expansion was due to the strong binding between Al4Er phases and surrounding organization, whereas the continuous concave and convex interface structure of Al4Er provided a significant meshing effect on the matrix and the eutectic structure.

scholarly journals TEM observation of precipitates and their role to mechanical properties in Ti-5553 alloy heated to some temperatures up to 923 K

2020 ◽  
Vol 321 ◽  
pp. 11035
Author(s):  
E. Sukedai ◽  
E. Aeby-Gautier ◽  
M. Dehmas
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Hardening Mechanism ◽  
Transmission Electron ◽  
The Matrix ◽  
Higher Temperature ◽  
Shearing Mechanism ◽  
Hardness Values ◽  
Measured Hardness

A Ti-5553 specimen was continuously heated to 923 K and simultaneously in-situ HEXRD profiles were taken. In addition, specimens heated at the same rate to several temperatures up to 923 K and further quenched were observed by transmission electron microscopy. Based on both results obtained, transformation sequence was clarified, precipitations of ω-, α”iso- and α-phases were confirmed, and size and density of these precipitates were measured. Hardness values of those specimens were also measured. The hardening mechanism was considered as shearing-mechanism for specimens aged at lower temperatures and by-pass one for specimens aged at higher temperature. An attempt of distinction between α”iso - and α-precipitates was also tried. Both precipitates were in needle-like shape and a possibility was suggested by measuring angles between two needle-shape precipitates on {110} of the matrix and comparing with each other.

Quantitative Evaluation of Secondary Phases in a Weld Joint Made of COST F and FB2 Creep Resistant Steels

2017 ◽  
Vol 270 ◽  
pp. 183-188
Author(s):  
Dagmar Jandová
Keyword(s):  
Quantitative Evaluation ◽  
Creep Strength ◽  
Weld Joint ◽  
Precipitate Size ◽  
Secondary Phases ◽  
Creep Tests ◽  
Transmission Electron ◽  
Creep Resistant Steels ◽  
Term Creep

Conventional (CCT) and accelerated (ACT) creep tests of a weld joint made of COST F and COST FB2 steels were carried out over a temperature range from 550 °C to 650 °C. Fracturing of the crept specimens was located in the heat affected zone (HAZ) of the F steel. Two specimens were selected after CCT and ACT for quantitative evaluation of the precipitates and compared to the weld joint in as-received conditions. Scanning and transmission electron micrographs were used to measure the precipitate size. Both methods were compared and the accuracy of the results was discussed. It was concluded that ACT can simulate the precipitation of chromium carbides and structure recovery during long term creep exposures. However, precipitation of Laves phase during CCT was not recorded after ACT. Therefore, it is difficult to use ACT in this experiment for estimating the long term creep strength.

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