scholarly journals Effect of Dislocation Slip Mechanism under the Control of Oxygen Concentration in Alpha-Case on Strength and Ductility of TC4 Alloy

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1057
Author(s):  
Xin Feng ◽  
Yilong Liang ◽  
Hao Sun ◽  
Shu Wang
Keyword(s):  
Electron Microscopy ◽  
Oxygen Concentration ◽  
Oxygen Diffusion ◽  
Negative Impact ◽  
Dislocation Slip ◽  
Slip Mechanism ◽  
Alpha Case ◽  
Lower Oxygen ◽  
Tc4 Alloy ◽  
Strength And Ductility

The oxygen diffusion layer (alpha-case) is generally considered to have a negative impact on the mechanical properties and applications of titanium alloys. In this study, TC4 alloy specimens with four types of different oxygen concentrations in alpha-case were obtained by controlling the oxygen diffusion process parameters. Scanning electron microscopy and glow discharge spectrometry were employed to characterize the microstructure and oxygen concentration of alpha-case. The effect of alpha-case on strength and ductility of TC4 alloy was investigated via tensile test and new insights were provided. The results indicate that with the increase in the oxygen concentration in the alpha-case, the ductility of the TC4 alloy gradually decreased. Interestingly, the strength of TC4 alloy with the alpha-case first increased and then decreased, resulting in the existence of a peak corresponding to a lower oxygen concentration before the decline of strength. Furthermore, a relatively good ductility match was also observed at the peak. When the oxygen concentration was relatively high, both the strength and ductility decreased. This phenomenon is attributed to the fact that dislocations in the alpha-case controlled by the oxygen concentration were modified from wavy slip to planar slip. Finally, the dislocation’s slip morphology was characterized by transmission electron microscopy.

Low-temperature annealing of YBa2Cu3O7-x

1992 ◽  
Vol 50 (1) ◽  
pp. 88-89
Author(s):  
R.L. Sabatini ◽  
Yimei Zhu ◽  
Masaki Suenaga ◽  
A.R. Moodenbaugh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Oxygen Diffusion ◽  
Diffusion Rate ◽  
Oxygen Depletion ◽  
Low Temperature Annealing ◽  
Transmission Electron ◽  
Microstructural Effects ◽  
Oxygen Diffusion Rate

Low temperature annealing (<400°C) of YBa2Cu3O7x in a ozone containing oxygen atmosphere is sometimes carried out to oxygenate oxygen deficient thin films. Also, this technique can be used to fully oxygenate thinned TEM specimens when oxygen depletion in thin regions is suspected. However, the effects on the microstructure nor the extent of oxygenation of specimens has not been documented for specimens exposed to an ozone atmosphere. A particular concern is the fact that the ozone gas is so reactive and the oxygen diffusion rate at these temperatures is so slow that it may damage the specimen by an over-reaction. Thus we report here the results of an investigation on the microstructural effects of exposing a thinned YBa2Cu3O7-x specimen in an ozone atmosphere using transmission electron microscopy and energy loss spectroscopy techniques.

The composition and structure of SIPOS: A high spatial resolution electron microscopy study

1993 ◽  
Vol 8 (11) ◽  
pp. 2893-2901 ◽  
Author(s):  
M. Catalano ◽  
M.J. Kim ◽  
R.W. Carpenter ◽  
Das K. Chowdhury ◽  
Joe Wong
Keyword(s):  
Electron Microscopy ◽  
Oxygen Concentration ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Isothermal Transformation ◽  
Electron Microscopy Study ◽  
Precipitation Reaction ◽  
Free Zone ◽  
Resolution Electron ◽  
Chemical Distribution

The nanostructure and chemical distribution in semi-insulating polycrystalline oxygen-doped silicon (SIPOS) deposited on (001) Si and its isothermal transformation behavior at 900 °C were investigated by high resolution electron microscopy (HREM) and electron energy loss nanospectroscopy (EELS). The structure of the as-deposited film, which contained 15 at. % oxygen, was amorphous. No evidence for nanocrystalline second phases was found. It was similar in appearance to amorphous silicon. After annealing for 30 min at 900 °C in an inert environment (N2), a dispersion of small nanocrystals, identified as silicon by imaging, diffraction and EELS, formed in the amorphous SIPOS matrix, with a thin precipitate free zone (PFZ) adjacent to the Si substrate. The SIPOS matrix oxygen concentration increased to 36 at. % and the matrix remained amorphous after annealing. No other phases were observed in annealed specimens. Changes in Si–L near edge fine structure and low loss peaks in EELS spectra from SIPOS with increasing oxygen concentration indicated that it is a solid solution supersaturated with silicon. Microstructures indicated that the Si nanocrystals formed during a homogeneous precipitation reaction.

Tribocorrosion Behaviors of D40 Steel in Artificial Seawater

2017 ◽  
Vol 898 ◽  
pp. 840-848
Author(s):  
Liang Shi ◽  
Shao Peng Qu ◽  
Hai Yan Chen ◽  
Yan Sheng Yin ◽  
Li Jing Yang
Keyword(s):  
Electron Microscopy ◽  
Oxygen Diffusion ◽  
Energy Dispersive Spectrometry ◽  
Diffusion Rate ◽  
Corrosion Process ◽  
Ion Adsorption ◽  
White Light Interferometry ◽  
Friction Process ◽  
Surface Morphologies ◽  
Scanning Electron

The friction, corrosion and tribocorrosion experiments were carried out to study the tribocorrosion characteristics of the D40 steel. Friction process was undertaken using a TriboLab. The electrochemical property of D40 steel was studied using an electrochemical workstation. The surface morphologies of the D40 steel after experiments were characterized by white light interferometry, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results indicated that both the tribocorrosion and corrosion process of D40 steel under the condition of seawater were controlled by the cathodic oxygen diffusion. The diffusion rate of oxygen in the solution was accelerated by the friction. The phenomenon of Cl ion adsorption was more obvious for the D40 steel during tribocorrosion test, and the corrosion resistance was significantly reduced due to the promotion of friction.

Evaluation of 4330M Steel for Fasteners Applications

2017 ◽  
Vol 380 ◽  
pp. 198-211 ◽  
Author(s):  
A. Al Sumait ◽  
C. Delgado ◽  
F. Aldhabib ◽  
X. Sun ◽  
F. Alzubi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Tensile Testing ◽  
Grain Structure ◽  
Hardness Testing ◽  
Heat Treated ◽  
Different Types ◽  
Strength And Ductility ◽  
Scanning Electron

The objective of the study was to optimize the strength and ductility values of the 4330M steel. Optimization was conducted through different types of heat treatments. Tensile testing, hardness testing, optical microscopy, and Scanning Electron Microscopy (SEM) were used to evaluate the mechanical properties and microstructure of the as-received and the heat treated samples. The alloy was provided from two vendors; vendor H and vendor S. Results showed that by increasing the tempering temperatures, strength values decreases, while ductility values remain unchanged. Vendor H samples had higher strength values and much finer grain structure which was revealed only at 5000x magnification.

Influence of some factors on oxygen uptake of canine cardiac Purkinje fibers

1963 ◽  
Vol 204 (1) ◽  
pp. 5-8 ◽  
Author(s):  
Kalman Greenspan ◽  
Paul F. Cranefield
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Concentration ◽  
Diffusion Limitation ◽  
Purkinje Fibers ◽  
Ambient Oxygen ◽  
Cardiac Purkinje Fibers ◽  
Lower Oxygen ◽  
Wet Weight ◽  
Oxygen Tensions ◽  
Oxygen Concentrations

The rate of oxygen uptake of quiescent Purkinje fibers of the dog's heart was determined using a flow respirometer and oxygen polarography. At ambient oxygen concentrations of 60% or higher the rate of uptake was 0.739 mm3/mg wet weight per hr at 35 C. The temperature coefficient over the range 25–35° was 2.3. The uptake was independent of the ambient oxygen concentration at oxygen concentrations equal to or greater than 60% of an atmosphere. In lower oxygen concentrations the rate of uptake was found to be depressed. The depression of uptake in the lower oxygen tensions is probably the result of diffusion limitation; it may, however, reflect dependence of resting uptake on oxygen concentration.

Formation of Nanosized Metallic Ag Grains by Oxidation of Ag Single Crystals with Hyperthermal Atomic Oxygen

2003 ◽  
Vol 788 ◽  
Author(s):  
Long Li ◽  
Judith C. Yang
Keyword(s):  
Electron Microscopy ◽  
Single Crystals ◽  
Oxygen Diffusion ◽  
Atomic Oxygen ◽  
Lattice Expansion ◽  
Oxide Scales ◽  
Microstructural Investigation ◽  
Transmission Electron ◽  
Polycrystalline Silver ◽  
Silver Grains

ABSTRACTSilver single crystals (Ag(100), Ag(111)) were exposed to 5eV hyperthermal atomic oxygen, created by a laser detonation of molecular oxygen at a substrate temperature of 220°C for 7 hours. Oxide scales of more than ten microns formed on both Ag (100) and Ag (111) substrates. The microstructural investigation of the oxide layers by high resolution transmission electron microscopy (HRTEM) revealed that the “oxide” scales are predominately composed of nanosized polycrystalline silver grains (5–100nm) as well as a small amount of nanosized silver oxides. The results were remarkably different than the O2 oxidation. The HRTEM investigation suggested that the grains of polycrystalline silver were first carved off from the substrate into “oxide” scale by lattice expansion and decohesion, which are driven by atomic oxygen diffusion in Ag lattice, occupation of oxygen atoms at the interstitial sites of Ag lattice, and partially internal oxidation. The grains in the scale were also subject to continuing oxidations with the atomic oxygen--secondary poly-crystallization, and changed to smaller grains. The preferred oxidation fronts in silver lattice is along the {111} planes.

High Strain Rate Superplasticity and Microstructure Evolution in a Coarse-Grained Mg-Gd-Y-Zr Rolled Sheet

2014 ◽  
Vol 900 ◽  
pp. 719-724
Author(s):  
Ying Zheng ◽  
Chang Ping Tang ◽  
Yun Lai Deng
Keyword(s):  
Electron Microscopy ◽  
Dynamic Recrystallization ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Microstructural Analysis ◽  
Alloy Sheet ◽  
Coarse Grained ◽  
Dislocation Slip ◽  
Rolled Sheet

Superplasticity at high deformation rates is desirable in order to make superplastic forming more practical. High strain rate superplastic behavior and microstructure of the rolled Mg-Gd-Y-Zr alloy sheet were investigated. For the purposes, tensile tests at the strain rate of 0.01 s-1were conducted, which revealed that the sheet exhibited elongations of 180%~266%. Post-deforming microstructures were characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy, while crystallographic orientation information was obtained from macro-texture analysis. The results show that the high strain rate superplasticity was attributed to class-I creep accommodated by dynamic recrystallization. It is suggested from microstructural analysis results that the interaction between second phases and dislocation facilitated dynamic recrystallization. The macro-texture at the strain of 0.8 still exhibited some characteristics of the crystal rotation arising from dislocation slip despite the occurrence of DRX.

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