Microstructure and Property Change of Ti-49Al Induced by Hydrogen Charging

2000 ◽  
Vol 646 ◽  
Author(s):  
E. Abe ◽  
K.W. Gao ◽  
M. Nakamura
Keyword(s):  
Atmospheric Pressure ◽  
Single Phase ◽  
Amorphous Region ◽  
Hydrogen Gas ◽  
In Situ Tem ◽  
Al Alloy ◽  
Two Phase ◽  
Hydrogen Charging ◽  
Nano Crystalline

ABSTRACTWe have investigated an effect of hydrogen gas-charging on the microstructure and the mechanical property of a Ti-49at.%Al alloy. After hydrogen-charging performed under an atmospheric pressure of hydrogen gas at 1023K for 3 hours, the alloy with γ-single phase has become completely brittle, while this hydrogen-induced embrittlement is suppressed for that with (γ+α2) two-phase microstructure composed of lath-precipitates in the γ matrix. A significant microstructural change was found to occur for the two-phase alloy (approximately 340ppm hydrogen in the alloy); a thin amorphous layers with a few nm thickness appear at the preexisting γ/α2 interfaces in the lath-precipitates after hydrogen-charging. In-situ TEM observation confirmed that the amorphous region transforms to a nano-crystalline state after heating to 1000K at which the hydrogen could be removed (degassed), indicating that the amorphous phase is not a binary Ti-Al phase but a ternary Ti-Al-H one. This, in turn, suggests that the γ/α2 interface in the lath packets act as the most preferential sites for hydrogen storage. Therefore, the scavenging is expected to occur effectively for the microstructure composed of γ-α2 fine lamellae in which a large number of γ/α2 interfaces exist. It is worthwhile mentioning that the fine-scale of the lamellae makes it possible to have a large number of interfaces for a given volume of the α2 phase.

Studies of phase transformation of Fe1-xS by in Situ TEM

1989 ◽  
Vol 47 ◽  
pp. 648-649
Author(s):  
Thao A. Nguyen ◽  
Linn W. Hobbs
Keyword(s):  
Phase Transformation ◽  
Single Phase ◽  
Nucleation And Growth ◽  
In Situ Tem ◽  
Two Phase ◽  
S Matrix ◽  
In Situ Heating ◽  
Phase Mixture ◽  
Lamellar Type

The transformation from Fe1-xS (IC) phase to a mixture of FeS (2C) and iron poor Fe1-xS (IC) phases has been investigated by a series of in-situ heating experiments. The purpose of this study is to resolve the controversy over the mechanism of phase transformation (spinodal decomposition versus nucleation and growth) and to explain the different microstructures observed in the two phase mixture of FeS and Fe1-xS (Figure 1).In-situ heating experiments were carried out using a JEOL JEM EM-SHTH double tilt heating holder. Synthetic “single” Fe0.97S crystals were cut into 3 mm disks, mechanically and ion thinned to electron transparency. In all cooling experiments, the sample was first held at 390 K, a temperature above the transition temperature in order to generate an initial single phase material; then, the temperature was quickly reduced to the temperature of interest.Figure 2a shows the development of a lamellar type microstructure after the sample's temperature was reduced from 390 K to 363 K and then held at this temperature for ten minutes. At 363 K, the undercooling is 27 K. The troilite FeS (2C) phase heterogeneously nucleates and grows along the edge of the sample. Diffraction analysis shows that the FeS (2C) phase is embedded in the iron-poor Fe1-x,S matrix with a rod-like structure.

scholarly journals Further insights into the Fe(ii) reduction of 2-line ferrihydrite: a semi in situ and in situ TEM study

2020 ◽  
Vol 2 (10) ◽  
pp. 4938-4950
Author(s):  
Mario Alberto Gomez ◽  
Ruonan Jiang ◽  
Miao Song ◽  
Dongsheng Li ◽  
Alan Scott Lea ◽  
...  
Keyword(s):  
Catalytic Reduction ◽  
In Situ Tem ◽  
Nano Crystalline

The catalytic reduction of nano-crystalline 2-line ferrihydrite with Fe(ii)(aq) doesn't occur via direct pathways but rather through new intermediate steps.

scholarly journals EXCHANGE COUPLING AND ENHANCEMENT OF CURIE TEMPERATURE OF THE INTERGRANULAR AMORPHOUS REGION IN NANO-CRYSTALLINE DUPLEX-PHASE ALLOYS SYSTEM

2007 ◽  
Vol 21 (27) ◽  
pp. 4689-4706
Author(s):  
Y. Z. SHAO ◽  
W. R. ZHONG ◽  
G. M. LIN ◽  
X. D. HU
Keyword(s):  
Curie Temperature ◽  
Exchange Coupling ◽  
Volume Fraction ◽  
Amorphous Region ◽  
Experimental Result ◽  
Dual Phase ◽  
Two Phase ◽  
Nanocrystallite Size ◽  
Nano Crystalline ◽  
Two Component

We studied the theoretical Curie temperature of a dual-phase nanomagnetic system by Monte Carlo simulation of a modified Heisenberg model on a 3D complex lattice consisting of single- and cluster-spins. We also systematically investigated the experimental Curie temperature of a dual-phase nanomagnetic alloy and performed a direct comparison between theory and experiment. The exchange coupling between two component magnetic phases substantially affects the Curie temperature [Formula: see text] of the intergranular amorphous region of a dual-phase nanomagnetic system. The [Formula: see text] depends upon the nanocrystallite size d, the volume fraction Vc and the interspace among crystallites ξ. Large crystallized volume fraction Vc, small grain size d, and thin interphase thickness ξ lead to an obvious enhancement of Curie temperature (ECT) of intergranular amorphous region, whereas the Curie temperature of nanocrystallites [Formula: see text] decreases slightly. By simulation, we worked out a relationship between the reduced ECT and ξ, as [Formula: see text], and it conforms to the experimental result. In addition, we also simulated the demagnetization of a hard–soft nanocomposite system. The exchange coupling between two component phases affects the cooperativity of two-phase magnetizations, the coherent reversal of magnetizations, and coercivity.

scholarly journals Rheology-based method for calculating polymer inaccessible pore volume in core flooding experiments

2019 ◽  
Vol 89 ◽  
pp. 04001 ◽  
Author(s):  
V. H. S. Ferreira ◽  
R. B. Z. L. Moreno
Keyword(s):  
Shear Rate ◽  
Pore Volume ◽  
Single Phase ◽  
Relative Difference ◽  
Core Flooding ◽  
Two Phase ◽  
Shear Rates ◽  
The Core ◽  
Inaccessible Pore Volume

Polymer flooding is an enhanced oil recovery (EOR) method that reduces the mobility ratio between the displaced oil and the displacing injected water. The flow of polymer solutions through porous media is subject to some process-specific phenomena, such as the inaccessible pore volume (IAPV). Due to IAPV, polymer molecules move faster through the porous medium than smaller ones. Thus the IAPV value needs to be accounted for in experiments and field projects. Recent reports found that polymer in-situ rheology correlates with the IAPV. The objective of this paper is to develop a method for estimating IAPV based on the in-situ rheology of polymers. The methodology proposed here can be used in both single- and two-phase experiments. The technique requires measurement of polymer resistance factor (RF) and residual resistance factor (RRF) at steady state conditions. Core permeability, porosity, and residual oil saturation, as well as water and polymer bulk viscosities, also need to be taken into account. Correlations for polymer in-situ viscosity and shear rate are solved simultaneously, to wield an estimative for the IAPV. Aiming at to prove the method, we report 16 core-flooding experiments, eight single- and eight two-phase experiments. We used a flexible polymer and sandstone cores. All the tests were run using similar rock samples. In the single-phase experiments, we compare the alternative method with the classic tracer method to estimate IAPV. The results show an average relative difference of 11.5% between the methods. The two-phase results display, on average, an 18% relative difference to the IAPV measured in the single-phase experiments. The difference between single- and two-phase results can be an effect of the higher shear rates experienced in the two-phase floodings since, in these cases, the aqueous phase shear rate is also dependent on the phase saturation. Additionally, temperature, core length, pore pressure, and iron presence on the core did not show any influence on the IAPV for our two-phase experiments. The method proposed in this paper is limited by the accuracy of the pressure drop measurements across the core. For flexible polymers, the method is valid only for low and mid shear rates, but, accoording to literature, for rigid polymers the method should be accurate for a broad range of shear rates. The method proposed here allows the measurement of polymer IAPV on two- and single- phase core-flooding experiments when a tracer is not used.

scholarly journals In situ TEM Observation of MultiLayer Graphene Formation from CO on Cobalt Nanoparticles at Atmospheric Pressure

2017 ◽  
Vol 23 (S1) ◽  
pp. 896-897 ◽  
Author(s):  
G. Marien Bremmer ◽  
Eirini Zacharaki ◽  
Anja O. Sjastad ◽  
Violeta Navarro ◽  
Joost W. M. Frenken ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Cobalt Nanoparticles ◽  
In Situ Tem ◽  
Multilayer Graphene

In situ TEM studies of the shape evolution of Pd nanocrystals under oxygen and hydrogen environments at atmospheric pressure

2017 ◽  
Vol 53 (99) ◽  
pp. 13213-13216 ◽  
Author(s):  
Xun Zhang ◽  
Jun Meng ◽  
Beien Zhu ◽  
Jian Yu ◽  
Shihui Zou ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
In Situ Tem ◽  
Shape Evolution

The shape evolutions of Pd nanocrystals under oxygen and hydrogen environments at atmospheric pressure were studied using in situ TEM.

Microstructure and Mechanical Properties of Al Added Ni3(Si,Ti) Intermetallic Thin Sheets

2010 ◽  
Vol 654-656 ◽  
pp. 480-483
Author(s):  
Yasuyuki Kaneno ◽  
Yasunori Fujimoto ◽  
Takayuki Takasugi
Keyword(s):  
High Temperature ◽  
Single Phase ◽  
Thermomechanical Processing ◽  
Al Alloy ◽  
Thin Sheets ◽  
Intermetallic Alloys ◽  
Ordered Structure ◽  
Two Phase ◽  
Cold Rolled ◽  
High Temperature Tensile

The effect of Al addition on microstructures and tensile properties of cold-rolled Ni3(Si,Ti) intermetallic alloys with L12 ordered structure, which were fabricated through thermomechanical processing from arc-melted ingots, were investigated. Addition of 4 and 8 at.% Al to Ni3(Si,Ti) was conducted in two ways that Al substituted for Ti site and both for Ni and Ti sites, respectively. The alloys made by the former way showed a two-phase microstructure consisting of disordered fcc Ni solid solution dispersions in the L12 matrix, irrespective of Al contents, while the 4 at.% Al alloy made by the latter way exhibited an L12 single-phase microstructure. These alloys were successfully cold-rolled to thin sheets with a thickness of 200 μm except the 8 at.% Al alloy made by the latter way. For the thermomechanically processed 4 at.% Al alloys, high-temperature yield stress was higher in the alloy made by the latter way than in the alloy made by the former one, suggesting that the single-phase microstructure consisting of whole L12 ordered structure is favorable for high-temperature tensile property.

TEM Studies of Shear Bands in a Bulk Metallic Glass Based Composite

2001 ◽  
Vol 7 (S2) ◽  
pp. 1120-1121
Author(s):  
E. Pekarskaya ◽  
C.P. Kim ◽  
W.L. Johnson
Keyword(s):  
Metallic Glasses ◽  
Shear Bands ◽  
High Yield ◽  
In Situ Tem ◽  
Two Phase ◽  
University Of Illinois ◽  
Glass Forming ◽  
The University ◽  
Very High

In 1980’s the discovery of multicomponent systems with exceptional glass forming ability enabled the synthesis of metallic glasses at relatively low cooling rates, 10−1 — 102 K/s and at a larger thicknesses. Bulk metallic glasses normally have very high yield stress, σy = 0.02 · Y (Y is Young’s modulus), high elastic limit of about 2%, but fail with very little global plasticity, typically along a localized shear band at a 45 degree angle with respect to the applied stress.The material studied in the present work is a two-phase Zr56.3Ti13.8Cu6.9Ni5.6Nb5.0Be12.5 alloy,prepared by in-situ processing. The alloy consists of amorphous and crystalline phases. In-situ TEM straining (tensile) experiments were performed at room temperature in JEOL 4000EX operating at 300kV. The experiments were carried out in the Center for Microanalysis of Materials in the University of Illinois at Urbana-Champaign. The goal of the study was to understand the deformation mechanisms of such composite material.

scholarly journals Thermal behavior of Pd@SiO2 nanostructures in various gas environments: a combined 3D and in situ TEM approach

Nanoscale ◽  
2018 ◽  
Vol 10 (43) ◽  
pp. 20178-20188 ◽  
Author(s):  
Walid Baaziz ◽  
Mounib Bahri ◽  
Anne Sophie Gay ◽  
Alexandra Chaumonnot ◽  
Denis Uzio ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Thermal Behavior ◽  
Atmospheric Pressure ◽  
Electron Tomography ◽  
Core Shell ◽  
In Situ Tem ◽  
Environmental Tem ◽  
First Time ◽  
Thermal Stability Of

The thermal stability of core–shell Pd@SiO2 was for the first time monitored by using in situ Environmental TEM at atmospheric pressure coupled with Electron Tomography on the same particles.

In-Situ TEM Observation of Electromigration Damage by Surface or Interface Diffusion in Al and Al Alloy Films

1991 ◽  
Vol 225 ◽  
Author(s):  
C. Y. Chang ◽  
R. W. Vook
Keyword(s):  
Grain Size ◽  
Diffusion Mechanism ◽  
In Situ Tem ◽  
Al Alloy ◽  
Linear Temperature ◽  
Alloy Films ◽  
Interface Diffusion ◽  
Transmission Electron ◽  
Dc Current

ABSTRACTIn-situ transmission electron microscope (TEM) electromigration damage (EMD) tests were performed on pure Al films which were thermally evaporated onto oxidized silicon wafers under different deposition conditions. Three different aluminum alloy films, Al-2wt%Cu, Al-8wt%Cu, and Al-2wt%Cu-lwt%Si were also examined. TEM images were recorded photographically and by a video camcorder. The sample stripes were stressed by a high DC current density (≈1.5 MA/cm2). A linear temperature ramp (5°C/min) was supplied by an external, computer controlled heater. The morphology of EMD-induced voids was found to be strongly dependent on microstructure. In small grain size Al stripes, EMD occurred by the formation of void “fingers” which propagated in an almost random manner. In large grain size Al and Al alloy stripes, the EMD-elongated voids propagated approximately parallel to each other and along the field direction. They were preceded with clearly identifiable local thinning. The thinned regions often had crystallographic edges. Contrary to the commonly held belief that EMD occurs only by a grain boundary diffusion mechanism, the present study clearly shows that surface or interface diffusion was the dominant, latter stage EMD failure mode in large grain size films.

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