scholarly journals Effects of Withdrawal Rate on the Microstructure of Directionally Solidified GH4720Li Superalloys

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 771
Author(s):  
Jinglong Qu ◽  
Shufeng Yang ◽  
Zhengyang Chen ◽  
Jingshe Li ◽  
Anping Dong ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Electron Probe ◽  
Phase Distribution ◽  
Growth Zone ◽  
Withdrawal Rate ◽  
Directionally Solidified ◽  
Alloying Element ◽  
Stable Growth ◽  
Average Size ◽  
Scanning Electron

Increasing the ingot size of GH4720Li superalloys makes it difficult to control their microstructure, and the withdrawal rate is an important factor in controlling and refining the microstructure of GH4720Li superalloys. In this study, GH4720Li superalloy samples were prepared via Bridgman-type directional solidification with different withdrawal rates. The morphology and average size of the dendrites in the stable growth zone during directional solidification in each sample, morphology and average size of the γ’ phases, and microsegregation of each alloying element were analyzed using optical microscopy, Photoshop, Image Pro Plus, field emission scanning electron microscopy, and electron probe microanalysis. Increasing the withdrawal rate significantly helped in refining the superalloy microstructure; the average secondary dendrite arm spacing decreased from 133 to 79 µm, whereas the average sizes of the γ’ phases in the dendrite arms and the interdendritic regions decreased from 1.02 and 2.15 µm to 0.69 and 1.26 µm, respectively. Moreover, the γ’ phase distribution became more uniform. The microsegregation of Al, Ti, Cr, and Co decreased with the increase in the withdrawal rate; the segregation coefficients of Al, Cr, and Co approached 1 at higher withdrawal rates, whereas that of Ti remained above 2.2 at all the withdrawal rates.

scholarly journals Investigation of Microstructure Evolution and Phase Selection of Peritectic Cuce Alloy During High-Temperature Gradient Directional Solidification

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 911
Author(s):  
Yiku Xu ◽  
Zhaohao Huang ◽  
Yongnan Chen ◽  
Junxia Xiao ◽  
Jianmin Hao ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Primary Dendrite ◽  
Primary Phase ◽  
Withdrawal Rate ◽  
Compressive Property ◽  
Directionally Solidified ◽  
Phase Selection ◽  
Coupled Growth ◽  
Selection Of

In this work, a CuCe alloy was prepared using a directional solidification method at a series of withdrawal rates of 100, 25, 10, 8, and 5 μm/s. We found that the primary phase microstructure transforms from cellular crystals to cellular peritectic coupled growth and eventually, changes into dendrites as the withdrawal rate increases. The phase constituents in the directionally solidified samples were confirmed to be Cu2Ce, CuCe, and CuCe + Ce eutectics. The primary dendrite spacing was significantly refined with an increasing withdrawal rate, resulting in higher compressive strength and strain. Moreover, the cellular peritectic coupled growth at 10 μm/s further strengthened the alloy, with its compressive property reaching the maximum value of 266 MPa. Directional solidification was proven to be an impactful method to enhance the mechanical properties and produce well-aligned in situ composites in peritectic systems.

High Resolution Scanning Electron Microscopy

1991 ◽  
Vol 49 ◽  
pp. 478-479
Author(s):  
David Joy ◽  
James Pawley
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Beam ◽  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Electron Probe ◽  
Impact Point ◽  
Interaction Volume ◽  
Scanning Electron

The scanning electron microscope (SEM) builds up an image by sampling contiguous sub-volumes near the surface of the specimen. A fine electron beam selectively excites each sub-volume and then the intensity of some resulting signal is measured. The spatial resolution of images made using such a process is limited by at least three factors. Two of these determine the size of the interaction volume: the size of the electron probe and the extent to which detectable signal is excited from locations remote from the beam impact point. A third limitation emerges from the fact that the probing beam is composed of a finite number of discrete particles and therefore that the accuracy with which any detectable signal can be measured is limited by Poisson statistics applied to this number (or to the number of events actually detected if this is smaller).

The effect of back-melting on the continuity of crystallographic orientation and composition in HgZnTe

1992 ◽  
Vol 50 (2) ◽  
pp. 1696-1697
Author(s):  
H.J. Zuo ◽  
M.W. Price ◽  
R.D. Griffin ◽  
R.A. Andrews ◽  
G.M. Janowski
Keyword(s):  
Directional Solidification ◽  
Space Shuttle ◽  
Solidification Process ◽  
Space Experiment ◽  
Infrared Detection ◽  
Directionally Solidified ◽  
Crystallographic Defects ◽  
Semiconducting Alloys ◽  
Uniform Composition ◽  
Growth Experiments

The II-VI semiconducting alloys, such as mercury zinc telluride (MZT), have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities and crystallographic imperfections adversly affect the performance of MZT infrared detectors. One source of imperfections in MZT is gravity-induced convection during directional solidification. Crystal growth experiments conducted in space should minimize gravity-induced convection and thereby the density of related crystallographic defects. The limited amount of time available during Space Shuttle experiments and the need for a sample of uniform composition requires the elimination of the initial composition transient which occurs in directionally solidified alloys. One method of eluding this initial transient involves directionally solidifying a portion of the sample and then quenching the remainder prior to the space experiment. During the space experiment, the MZT sample is back-melted to exactly the point at which directional solidification was stopped on earth. The directional solidification process then continues.

Microstructure and microanalysis of sintered Fe-Nd-B permanent magnets

1990 ◽  
Vol 48 (4) ◽  
pp. 990-991
Author(s):  
Mahesh Chandramouli
Keyword(s):  
Electron Microscope ◽  
Liquid Phase ◽  
Permanent Magnets ◽  
Phase Distribution ◽  
Energy Dispersive Spectrometer ◽  
Nucleation And Growth ◽  
Liquid Phase Sintering ◽  
Domain Wall Energy ◽  
Oxide Phases ◽  
Scanning Electron

Magnetization reversal in sintered Fe-Nd-B, a complex, multiphase material, occurs by nucleation and growth of reverse domains making the isolation of the ferromagnetic Fe14Nd2B grains by other nonmagnetic phases crucial. The magnets used in this study were slightly rich in Nd (in comparison to Fe14Nd2B) to promote the formation of Nd-oxides at multigrain junctions and incorporated Dy80Al20 as a liquid phase sintering addition. Dy has been shown to increase the domain wall energy thus making nucleation more difficult while Al is thought to improve the wettability of the Nd-oxide phases.Bulk polished samples were examined in a JEOL 35CF scanning electron microscope (SEM) operated at 30keV equipped with a Be window energy dispersive spectrometer (EDS) detector in order to determine the phase distribution.

Eutectic formation during directional solidification: Effect of the withdrawal rate

2013 ◽  
Vol 92 ◽  
pp. 317-320 ◽  
Author(s):  
Sainan Yuan ◽  
Lina Jia ◽  
Limin Ma ◽  
Hua Jiang ◽  
Hu Zhang
Keyword(s):  
Directional Solidification ◽  
Withdrawal Rate ◽  
Eutectic Formation

scholarly journals Influence of reducing agents and surfactants on size and shape of silver fine powder particles

2014 ◽  
Vol 20 (2) ◽  
pp. 73-88 ◽  
Author(s):  
Stevan P. Dimitrijević ◽  
Željko Kamberović ◽  
Marija Korać ◽  
Zoran Anđić ◽  
Silvana Dimitrijević ◽  
...  
Keyword(s):  
Chemical Reduction ◽  
Nitrate Solution ◽  
Fine Powder ◽  
Production Scale ◽  
Scale Reduction ◽  
Primary Particles ◽  
Powder Particles ◽  
Different Shapes ◽  
Average Size ◽  
Scanning Electron

Silver fine powder with different shapes and sizes were prepared by chemical reduction and characterized by scanning electron microscope. In this paper was presented the method for the preparation of the fine Ag powder with particles size smaller than 2.5 µm with suitability for the mass-production scale. Reduction was performed from nitrate solution directly by vigorous stirring at room temperature by three different reduction agents, with and without presence of two dispersants. Scanning electron microscopy revealed the preferred size of the particles obtained in all experiments with aim of the protecting agent. Larger particles and wider size distribution were obtained without surfactants although with average size of about 1 µm and small quantity of larger clusters of primary particles that is out of the fine powder classification. High purity, 99.999%, of silver was obtained in every experiment. 

scholarly journals Solid-liquid interface morphology of white carbide eutectic during directional solidification

2017 ◽  
Vol 62 (1) ◽  
pp. 365-368 ◽  
Author(s):  
M. Trepczyńska-Łent
Keyword(s):  
Longitudinal Section ◽  
Argon Atmosphere ◽  
Liquid Interface ◽  
Interface Morphology ◽  
Directionally Solidified ◽  
Constant Temperature Gradient ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Scanning Electron ◽  
Made In

AbstractIn this paper the analysis of solid-liquid interface morphology in white carbide eutectic was made. In a vacuum Bridgman-type furnace, under an argon atmosphere, directionally solidified sample of Fe - C alloy was produced. The pulling rate was v = 125 μm/s (450 mm/h) and constant temperature gradient G = 33.5 K/mm. The microstructure of the sample was frozen. The microstructure of the sample was examined on the longitudinal section using an light microscope and scanning electron microscope.

Effect of microencapsulated chavil (Ferulago angulata) extract on physicochemical, microbiological, textural and sensorial properties of UF-feta-type cheese during storage time

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Fatemeh Borhanpour ◽  
Seyed Saeed Sekhavatizadeh ◽  
Saeid Hosseinzadeh ◽  
Mahboobeh Hasanzadeh ◽  
Mohammad-Taghi Golmakani ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Canola Oil ◽  
Storage Time ◽  
Streptococcus Thermophilus ◽  
Bimodal Distribution ◽  
Microscope Images ◽  
Average Size ◽  
Two Peaks ◽  
Scanning Electron ◽  
Microbiological Properties

Abstract Chavil (Ferulago angulata) extract (CE) and microencapsulated chavil extract (MCE) were added to UF- Feta-type Cheese. The aim of this study was to comprising CE and MCE on physicochemical and microbiological properties in cheese. The scanning electron microscope images demonstrate the MCE had elliptical shape. The average size diameter curve of the MCE revealed bimodal distribution with two peaks (1541 and 2222 nm) separately. The hardness value of MCE cheese (212.83 ± 17.63 g) was lower than that of CE (343.67 ± 25.53 g) because of canola oil used in the microencapsulation process. The MCE-cheese showed lower values of acidity (1.67%) in comparison with CE-cheese (1.87%). The viable numbers of Streptococcus thermophilus and Lactococcus lactis were equal among the samples (4.6–4.9 log10 CFU/g respectively). The acid degree value of MCE (2.07 ± 0.21%) and CE (1.83 ± 0.25%) cheese were nearly equal at the end of storage time.

scholarly journals Assessing the Physiological Relevance of Cough Simulators for Respiratory Droplet Dispersion

2020 ◽  
Vol 9 (9) ◽  
pp. 3002 ◽  
Author(s):  
Shiv H. Patel ◽  
Wonjun Yim ◽  
Anupam K. Garg ◽  
Sahil H. Shah ◽  
Jesse V. Jokerst ◽  
...  
Keyword(s):  
Droplet Size ◽  
Velocity Dispersion ◽  
Slow Motion ◽  
Limited Data ◽  
Droplet Dispersion ◽  
Physiological Relevance ◽  
Dispersion Velocity ◽  
Average Size ◽  
Spray Gun ◽  
Scanning Electron

Various breathing and cough simulators have been used to model respiratory droplet dispersion and viral droplets, in particular for SARS-CoV-2 modeling. However, limited data are available comparing these cough simulations to physiological breathing and coughing. In this study, three different cough simulators (Teleflex Mucosal Atomization Device Nasal (MAD Nasal), a spray gun, and GloGermTM MIST) that have been used in the literature were studied to assess their physiologic relevance. Droplet size, velocity, dispersion, and force generated by the simulators were measured. Droplet size was measured with scanning electron microscopy (SEM). Slow-motion videography was used to 3D reconstruct and measure the velocity of each simulated cough. A force-sensitive resistor was used to measure the force of each simulated cough. The average size of droplets from each cough simulator was 176 to 220 µm. MAD Nasal, the spray gun, and GloGermTM MIST traveled 0.38 m, 0.89 m, and 1.62 m respectively. The average velocities for the MAD Nasal, spray gun, and GloGermTM MIST were 1.57 m/s, 2.60 m/s, and 9.27 m/s respectively, and all yielded a force of <0.5 Newtons. GloGermTM MIST and the spray gun most closely resemble physiological coughs and breathing respectively. In conclusion, none of the simulators tested accurately modeled all physiologic characteristics (droplet size, 3-D dispersion velocity, and force) of a cough, while there were various strengths and weaknesses of each method. One should take this into account when performing simulations with these devices.

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