Study on Microstructure of Quenched Martensite in W6Mo5Cr4V2 Steel

2011 ◽  
Vol 295-297 ◽  
pp. 175-178
Author(s):  
Yun Ping Ji ◽  
Zong Chang Liu ◽  
Hui Ping Ren
Keyword(s):  
Phase Transformation ◽  
Small Area ◽  
Martensite Phase ◽  
Stacking Fault ◽  
Plate Martensite ◽  
Twin Crystal ◽  
Transmission Electron ◽  
Starting Point ◽  
Austenite Grains ◽  
The Difference

The microstructure and the formation mechanism of martensite in W6Mo5Cr4V2 steel was studied by metallographic microscope and JEM-2100 transmission electron microscope after the samples were austenized between the temperatures of Ac1~Accm and then quenched. The results show that When heating W6Mo5Cr4V2 steel samples between the temperatures of Ac1~Accm and then quenching, the cryptocrystalline martensite will be obtained. The cryptocrystalline martensite is plate martensite actually. It is considered that the formation cause of the cryptocrystal martensite is extremely inhomogeneous chemical composition in the austenite grains and the difference of martensite starting point (Ms point) of every small area in austenite grains. Besides the high-density dislocation and the fine twin crystal, the substructure of the cryptocrystalline martensite includes the superfine stacking fault. The stacking fault is caused by the stacking misarrangement during the crystal lattice reconstruction of martensite phase transformation. The midrib exists in the cryptocrystal martensite of W6Mo5Cr4V2 steel, which is composed of the fine twin crystal plates. The shear mechanism can not account for the formation of the martensite midrib.

scholarly journals Phase Transformation of High Velocity Air Fuel (HVAF)-Sprayed Al-Cu-Fe-Si Quasicrystalline Coating

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 834
Author(s):  
Mingwei Cai ◽  
Jun Shen
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
Amorphous Phase ◽  
High Velocity ◽  
Quasicrystalline Phase ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Heating And Cooling ◽  
Transmission Electron ◽  
The Difference

Al-Cu-Fe-Si quasicrystalline coatings were prepared by high velocity air fuel spraying to study their phase transformation during the process. The feedstock powder and coating were phase characterized by scanning electron microscopy, X-ray diffractometry, differential scanning calorimetry, and transmission electron microscopy. Results show that Al3Cu2 phase, a small amount of λ-Al13Fe4 phase, quasicrystalline phase (QC), amorphous phase, and β-Al (Cu, Fe, Si) phase were present in the sprayed Al50Cu20Fe15Si15 powder. For a typical flattened powder particle, the splat periphery was surrounded by a 1 µm thick amorphous phase. The inside area of the splat was composed of the QC covered by the Al3Cu2 and Si-rich β-Al (Cu, Fe, Si) phases. Another kind of Cu- rich β-Al (Cu, Fe, Si) phase can be found close to the amorphous area with a similar composition to the original β-Al (Cu, Fe, Si) phase in the powder. Different phases were observed when the periphery and inside area of the splat were compared. This result was caused by the difference in the heating and cooling rates.

The L12 to DO19 Phase Transformation In The Intermetallic Compound Fe3Ge

1997 ◽  
Vol 481 ◽  
Author(s):  
Q. Z. Chen ◽  
A. H. W. Ngan ◽  
B. J. Duggan
Keyword(s):  
Phase Transformation ◽  
Electron Microscope ◽  
Intermetallic Compound ◽  
Transmission Electron Microscope ◽  
Stacking Fault ◽  
Transmission Electron ◽  
Do19 Phase ◽  
Annealing Experiments

ABSTRACTA large kinetics hysteresis is found to exist between the forward and backward reactions of the L12 ↔ DO19 transformation in Fe3Ge. The slow DO19 to L12 transformation leaves behind very stable twins and stacking fault debris. In-situ annealing experiments in the transmission electron microscope revealed that nucleation for the reverse L12 to DO19 reaction takes place efficiently at these defects.

Cellular Domain Architecture of Stress-free Epitaxial Ferroelectric Films

2000 ◽  
Vol 655 ◽  
Author(s):  
S. P. Alpay ◽  
A. L. Roytburd ◽  
V. Nagarajan ◽  
L. A. Bendersky ◽  
R. Ramesh
Keyword(s):  
Phase Transformation ◽  
Structural Phase ◽  
Domain Architecture ◽  
Internal Stresses ◽  
X Ray Diffraction ◽  
Ferroelectric Films ◽  
Thermal Expansion Coefficients ◽  
Transmission Electron ◽  
Cellular Domain ◽  
The Difference

AbstractEpitaxial ferroelectric films undergoing a cubic-tetragonal phase transformation relax internal stresses due to the structural phase transformation and the difference in the thermal expansion coefficients of the film and the substrate by forming polydomain structures. The most commonly observed polydomain structure is the c/a/c/a polytwin that relieves the internal stresses only partially. Relatively thicker films may completely reduce internal stresses if all three variants of the ferroelectric phase are brought together such that the film has the same in-plane size as the substrate. In this article, we provide experimental evidence on the formation of the 3-domain structure based on transmission electron microscopy in 450 nm thick (001) PbZr0.2Ti0.8O3 films on (001) SrTiO3 grown by pulsed laser deposition. X-ray diffraction studies show that the film is fully relaxed. Experimental data is analyzed in terms of a domain stability map.

Effect of Microstructure Evolution and Corrosion Behavior on Phase Transformation of Nanocrystalline SUS304 Prepared by Dry Ice Shot Peening

2022 ◽  
Vol 10 (1) ◽  
pp. 9-14
Keyword(s):  
Corrosion Resistance ◽  
Phase Transformation ◽  
Electron Microscope ◽  
Corrosion Behavior ◽  
Shot Peening ◽  
Martensite Phase ◽  
Metallic Component ◽  
Dry Ice ◽  
High Deformation ◽  
Transmission Electron

Microstructure and corrosion behavior of nanocrystalline SUS304 by dry ice shot peening has been investigated in detail in term of phase transformation. SUS304 as metastable austenitic stainless has excellent corrosion resistance and induced martensite by shot peening process. However, the SUS304 has quite low strength which is difficult to wear as metallic component. The dry ice shot peening process was carried out on SUS304 surface for one and three hours. The microstructure was observed by transmission electron microscope (TEM) and scanning electron microscope (SEM) equipped with electron back-scattered diffraction (EBSD). The phase transformation was analyzed by X-ray diffraction (XRD). The corrosion testing was carried out in 3.5% NaCl solution. The result indicated that the grain size of SUS304 surface was finer by deformation due to dry ice shot peened process. The hardness was improved properly by the increasing the shot peened time, and the corrosion resistance was increased. The XRD results showed that three hours shot peening process induced martensite phase of SUS304 by 15 m thickness. It can be summarized that the dry ice shot peening can be induced phase transformation due to high deformation on the SUS304 surface

Analyses of Phase Transformation Mechanism Based on In Situ Observation during Ti-10Nb-5Sn Alloy Heating Cycles

2012 ◽  
Vol 549 ◽  
pp. 535-538
Author(s):  
Yan Li ◽  
Jie Qi ◽  
Chuan Xin Zhai ◽  
Ran Feng Qiu
Keyword(s):  
Phase Transformation ◽  
Electron Microscope ◽  
Shape Memory ◽  
Transmission Electron Microscope ◽  
Memory Function ◽  
Martensite Phase ◽  
Round Trip ◽  
Transformation Mechanism ◽  
Transmission Electron

The Ti-10Nb-5Sn alloy was heated and cooled repeatedly in a heater system located in transmission electron microscope chamber. The phase and morphology transformation was in situ observed to analyze the transformation mechanism from austenite β to martensite phase. The results reveal that he Ti-10Nb-5Sn alloy has round trip shape memory function.

Influence of Cell Wall Composition on the Fossilisation of Bacteria and the Implications for the Search for Early Life Forms

1997 ◽  
Vol 161 ◽  
pp. 491-504 ◽  
Author(s):  
Frances Westall
Keyword(s):  
Cell Wall ◽  
Life Forms ◽  
Cation Binding ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Transmission Electron ◽  
Hydrothermal Sediments ◽  
Identification Of Bacteria ◽  
The Difference

AbstractThe oldest cell-like structures on Earth are preserved in silicified lagoonal, shallow sea or hydrothermal sediments, such as some Archean formations in Western Australia and South Africa. Previous studies concentrated on the search for organic fossils in Archean rocks. Observations of silicified bacteria (as silica minerals) are scarce for both the Precambrian and the Phanerozoic, but reports of mineral bacteria finds, in general, are increasing. The problems associated with the identification of authentic fossil bacteria and, if possible, closer identification of bacteria type can, in part, be overcome by experimental fossilisation studies. These have shown that not all bacteria fossilise in the same way and, indeed, some seem to be very resistent to fossilisation. This paper deals with a transmission electron microscope investigation of the silicification of four species of bacteria commonly found in the environment. The Gram positiveBacillus laterosporusand its spore produced a robust, durable crust upon silicification, whereas the Gram negativePseudomonas fluorescens, Ps. vesicularis, andPs. acidovoranspresented delicately preserved walls. The greater amount of peptidoglycan, containing abundant metal cation binding sites, in the cell wall of the Gram positive bacterium, probably accounts for the difference in the mode of fossilisation. The Gram positive bacteria are, therefore, probably most likely to be preserved in the terrestrial and extraterrestrial rock record.

Destruction of Actin Filaments by Osmium Tetroxide

1977 ◽  
Vol 35 ◽  
pp. 466-467
Author(s):  
P. Maupin-Szamier ◽  
T. D. Pollard
Keyword(s):  
Actin Filaments ◽  
Time Course ◽  
Osmium Tetroxide ◽  
Rabbit Muscle ◽  
Muscle Actin ◽  
Sodium Phosphate Buffer ◽  
Transmission Electron ◽  
The Difference ◽  
Rates Of Decay ◽  
Short Time

We have studied the destruction of rabbit muscle actin filaments by osmium tetroxide (OSO4) to develop methods which will preserve the structure of actin filaments during preparation for transmission electron microscopy.Negatively stained F-actin, which appears as smooth, gently curved filaments in control samples (Fig. 1a), acquire an angular, distorted profile and break into progressively shorter pieces after exposure to OSO4 (Fig. 1b,c). We followed the time course of the reaction with viscometry since it is a simple, quantitative method to assess filament integrity. The difference in rates of decay in viscosity of polymerized actin solutions after the addition of four concentrations of OSO4 is illustrated in Fig. 2. Viscometry indicated that the rate of actin filament destruction is also dependent upon temperature, buffer type, buffer concentration, and pH, and requires the continued presence of OSO4. The conditions most favorable to filament preservation are fixation in a low concentration of OSO4 for a short time at 0°C in 100mM sodium phosphate buffer, pH 6.0.

Rocking Beam Microarea Diffraction Applied to Metallic thin Films

1976 ◽  
Vol 34 ◽  
pp. 396-397
Author(s):  
R. H. Geiss
Keyword(s):  
Thin Films ◽  
Electron Diffraction ◽  
Small Area ◽  
Objective Lens ◽  
Electron Optics ◽  
Metallic Thin Films ◽  
Transmission Electron Diffraction ◽  
Transmission Electron ◽  
Sample Height ◽  
Scanning Transmission

The theory and practical limitations of micro area scanning transmission electron diffraction (MASTED) will be presented. It has been demonstrated that MASTED patterns of metallic thin films from areas as small as 30 Åin diameter may be obtained with the standard STEM unit available for the Philips 301 TEM. The key to the successful application of MASTED to very small area diffraction is the proper use of the electron optics of the STEM unit. First the objective lens current must be adjusted such that the image of the C2 aperture is quasi-stationary under the action of the rocking beam (obtained with 40-80-160 SEM settings of the P301). Second, the sample must be elevated to coincide with the C2 aperture image and its image also be quasi-stationary. This sample height adjustment must be entirely mechanical after the objective lens current has been fixed in the first step.

Effects of dopant concentration on the microstructure of tin- doped indium oxide thin films

1990 ◽  
Vol 48 (4) ◽  
pp. 716-717
Author(s):  
I. A. Rauf
Keyword(s):  
Thin Films ◽  
Indium Oxide ◽  
Ionic Radius ◽  
Free Carrier ◽  
Electron Gun ◽  
Periodic Lattice ◽  
Oxide Thin Films ◽  
Transmission Electron ◽  
The Difference ◽  
Dopant Atoms

To understand the electronic conduction mechanism in Sn-doped indium oxide thin films, it is important to study the effect of dopant atoms on the neighbouring indium oxide lattice. Ideally Sn is a substitutional dopant at random indium sites. The difference in valence (Sn4+ replaces In3+) requires that an extra electron is donated to the lattice and thus contributes to the free carrier density. But since Sn is an adjacent member of the same row in the periodic table, the difference in the ionic radius (In3+: 0.218 nm; Sn4+: 0.205 nm) will introduce a strain in the indium oxide lattice. Free carrier electron waves will no longer see a perfect periodic lattice and will be scattered, resulting in the reduction of free carrier mobility, which will lower the electrical conductivity (an undesirable effect in most applications).One of the main objectives of the present investigation is to understand the effects of the strain (produced by difference in the ionic radius) on the microstructure of the indium oxide lattice when the doping level is increased to give high carrier densities. Sn-doped indium oxide thin films were prepared with four different concentrations: 9, 10, 11 and 12 mol. % of SnO2 in the starting material. All the samples were prepared at an oxygen partial pressure of 0.067 Pa and a substrate temperature of 250°C using an Edwards 306 coating unit with an electron gun attachment for heating the crucible. These deposition conditions have been found to give optimum electrical properties in Sn-doped indium oxide films. A JEOL 2000EX transmission electron microscope was used to investigate the specimen microstructure.

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