scholarly journals Size-Dependent Structural Properties of a High-Nb TiAl Alloy Powder

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 161 ◽  
Author(s):  
Binglin Liu ◽  
Maosong Wang ◽  
Yulei Du ◽  
Jingxiao Li
Keyword(s):  
Particle Size ◽  
High Temperature ◽  
Structural Properties ◽  
Structural Changes ◽  
Structural Characteristics ◽  
Nominal Composition ◽  
Induction Melting ◽  
Powder Size ◽  
Size Dependent ◽  
High Temperature Xrd

TiAl-based alloys are promising light weight structural materials for high temperature applications in the field of aerospace. Recently, fabrication technologies starting from powders including powder metallurgy and additive manufacturing have been developed to overcome the difficulties in the processing, machining and shaping of TiAl-based alloys. Spherical alloy powders with different particle size distributions are usually used in these fabrication techniques. The purpose of this study is to reveal the size-dependent structural properties of a high-Nb TiAl powder for these fabrication technologies starting from powders. A high-Nb TiAl pre-alloyed powder with nominal composition of Ti-48Al-2Cr-8Nb (at. %) was prepared by the electrode induction melting gas atomization (EIGA) method. The phase structure and morphology of the as-atomized powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The size-dependent structural changes of the as-atomized powders with different sizes were studied by differential scanning calorimetry (DSC) and in situ high temperature XRD. It was found that with decreasing the powder size, the content of the γ-TiAl phase decreases and the α2-Ti3Al phase increases. The α2-Ti3Al to γ-TiAl phase transformation was found in the temperature range of 600–770 °C. Based on the present work, the structural characteristics of TiAl powders are strongly dependent on their particle size, which should be considered in optimizing the process parameters of TiAl alloys fabricated from powders.

Analysis of Porosities in Nickel-Based Superalloys Powders

2020 ◽  
Vol 993 ◽  
pp. 327-332
Author(s):  
Le Biao Yang ◽  
Xiao Na Ren ◽  
Min Xia ◽  
Chang Chun Ge
Keyword(s):  
Particle Size ◽  
Formation Mechanism ◽  
Size Range ◽  
Nickel Base Superalloy ◽  
Induction Melting ◽  
Powder Size ◽  
Particle Size Range ◽  
Powder Diameter ◽  
Nickel Base ◽  
Base Superalloy

In this paper, we investigated the porosities and their formation mechanism in the nickel-base superalloy powders, which were prepared by electrode induction melting argon atomization and divided into four particle size ranges: d＜60μm, 60μm≤d＜120μm,120μm≤d＜180μm, and d≥180μm. Firstly, the distribution of porosities in the powder were observed by Zeiss electron microscope. Secondly, the number and size of porosities in different particle size range were counted. Finally, the formation mechanism of the porosity was analyzed in details. The results show that the porosities are mainly distributed at the edge and center of the powders, and the size increases with the increase of the powder size. the porosity varies from a few microns to dozens of microns. the biggest pore size in the powder is approximately 120μm.There are no obviously porosities found in powders when their diameters are less than 60μm. While the porosity appeared as the powder diameter is more than 60μm. In addition, the proportion of the powder with porosities also increases with increasing powder size. When powders size is more than 180μm, the proportion of the powder with porosities reached about 91%. In general, the formation of porosities in powders are mainly ascribed to two reasons. the first one is a portion of argon was enclosed by the metal films during the spheroidization; the second one is the metal droplets uneven shrinkage during the solidification.

scholarly journals Effect of Temperature, Pressure, Feed Particle Size, and Feed Particle Density on Structural Characteristics and Reactivity of Chars Generated during Gasification of Pittsburgh No.8 Coal in a High-Pressure, High-Temperature Flow Reactor

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4773
Author(s):  
Vijayaragavan Krishnamoorthy ◽  
Sarma V. Pisupati
Keyword(s):  
Particle Size ◽  
High Pressure ◽  
High Temperature ◽  
Flow Reactor ◽  
Particle Density ◽  
Structural Characteristics ◽  
Swelling Ratio ◽  
Group I ◽  
High Pressure High Temperature ◽  
Intrinsic Reactivity

The gasification behavior of coal under high-temperature and high-pressure conditions is important from the perspective of designing and optimizing high efficiency gasifiers and troubleshooting existing gasifiers. The effect of feed particle size, density, temperature, and pressure on char porous structure, morphology, reflectance, and reactivity under conditions relevant to entrained-flow gasification was investigated. The chars were generated over a range of temperatures (1100, 1300, and 1400 °C at 11.3 bar for the −150 + 106 µm fraction), pressures (3.4, 6.2, 11.3, 15.5, and 21.7 bar at 1300 °C for the −150 + 106 µm fraction), for various size fractions (−106 + 75, −150 + 106, −212 + 150, −420 + 212 µm at 1300 °C and 11.3 bar), and density fractions (<1.3, 1.3–1.6, >1.6g/cc for the −106 + 75 µm at 1300 °C and 11.3 bar) of Pittsburgh No.8 bituminous coal using a high-pressure, high-temperature flow reactor (HPHTFR) in a equimolar mixture of CO2 and N2. Chars were characterized for conversion, morphology, thermal swelling ratio, and reactivity using ash tracer technique, oil immersion microscopy, tap density technique, and a thermogravimetric analyzer, respectively, and the results were statistically analyzed to determine for effects by feed particle density, feed particle size, temperature, and pressure. The results showed that the conversion was most affected by temperature, followed by feed particle size, pressure, and feed particle density. In the case of structural characteristics (i.e., thermal swelling ratio and group-I char concentration), feed particle density affected group-I concentration, while both feed particle size and feed particle density affected thermal swelling ratio. Variation in vitrinite content and fragmentation affected the thermal swelling ratio and group-I char concentration. In the case of intrinsic reactivity, particle density showed the largest effect, followed by temperature, particle size, and pressure. An increase in reflectance and temperature was found to inversely affect intrinsic reactivity.

Compositional Optimization of In718 Superalloy Powder for Additive Manufacturing

2018 ◽  
Vol 941 ◽  
pp. 2167-2172
Author(s):  
Che Yi Lin ◽  
Hui Yum Bor ◽  
Chao Nan Wei ◽  
Chien Hung Liao
Keyword(s):  
Particle Size ◽  
High Temperature ◽  
Additive Manufacturing ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Gas Atomization ◽  
In718 Superalloy ◽  
Sieving Process ◽  
Superalloy Powder ◽  
Metal Droplets

In this research, a composition optimized In718 superalloy powder suitable for additive manufacturing has been developed by using the vacuum induction melting gas atomization (VIGA) and the powder sieving process. VIGA which combines the vacuum induction melting (VIM) and gas atomization (GA) processes uses high pressure inert gas to atomize the metal melt formed by VIM to form metal droplets. These metal droplets are solidified to form metal powders during the falling process in the atomized chamber. After the sieving process, the mean particle size D50 of the powder is less than 35 μm and the particle size distribution (PSD) ranges from 10 to 55 μm (D10~D90). Besides, the produced powder has high flowability (ICarr ≦15), which is suitable for selective laser melting (SLM) additive manufacturing (AM). After the SLM process, the tensile tests are conducted at room temperature and high temperature of 650°C. The results show that the high temperature properties of the optimized In718 superalloy are superior to the commercial In718 superalloy.

Effect of ultrasound on the structural characteristics of fresh skim milk

2019 ◽  
Vol 26 (3) ◽  
pp. 222-230
Author(s):  
Jitao Yang ◽  
Min Yang ◽  
Juanjuan Qin ◽  
Qiubing Zeng ◽  
Yucheng Wang ◽  
...  
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Structural Changes ◽  
Structural Characteristics ◽  
Skim Milk ◽  
Fluorescence Properties ◽  
Net Charge ◽  
Acid Sodium Salt ◽  
Α Helix ◽  
Β Sheet

The structural changes of skim milk caused by sonication were evaluated by particle size, zeta-potential, turbidity, scanning electron microscopy, Fourier transform infrared spectroscopy, and intrinsic and 8-anilino-1-naphthalenesulfonic acid sodium salt fluorescence properties. The results showed that the particle size and zeta-potential of skim milk remained constant with 1 min ultrasonication, and increased significantly when the duration of sonication was extended to 3 min. With 3–10 min ultrasonic treatment, the diameter and net charge of particles in skim milk changed scarcely. According to the topography, the integrity of casein micelles was not damaged by 30 min sonication, but the turbidity decreased sharply with sonication above 5 min. The secondary structure of protein in skim milk changed after 1 min sonication, shown by a significant increase of α-helix content and decrease in the irregularity of β-sheet. The intrinsic fluorescence intensity of skim milk with 1 min sonication increased dramatically with a shift in the maximum emission wavelength. The fluorescence properties revealed that the spatial structure of protein in skim milk changed by sonication.

Size Dependent Structural, Vibrational, and Luminescence Properties of Nanocrystalline LiIn(WO4)2:Cr3+

2008 ◽  
Vol 8 (7) ◽  
pp. 3545-3554 ◽  
Author(s):  
K. Hermanowicz ◽  
M. Maczka ◽  
P. E. Tomaszewski ◽  
L. Krajczyk ◽  
J. Hanuza ◽  
...  
Keyword(s):  
Particle Size ◽  
Structural Changes ◽  
Pechini Method ◽  
Phonon Coupling ◽  
Covalent Character ◽  
X Ray ◽  
Electron Transmission ◽  
Size Dependent ◽  
Electron Phonon Coupling ◽  
Critical Particle Size

X-ray, electron transmission spectroscopy, vibrational and luminescence studies of LiIn(WO4)2:Cr3+ nanoparticles prepared by Pechini method are reported. On annealing the sample several structural changes were observed resulting in a creation of three new, previously unknown polymorphs. It was shown that this tungstate undergoes two size-induced phase transitions from the structure similar to LiFe(WO4)2 into the structure similar to LiYb(WO4)2 and then into the structure of LiGa(WO4)2 type. These transitions occur for the critical particle size of about 100 and 30 nm, and they could be attributed mainly to some changes in the distribution of the sites occupied by Li+ and In3+ ions. Luminescence studies revealed decrease of the covalent character of chromium environment and electron–phonon coupling strength with decreasing size of the nanoparticles.

Diagnostic of Structural Changes in Ferromagnetic Powders during Milling in Beater Mill

2021 ◽  
Vol 316 ◽  
pp. 187-192
Author(s):  
I.N. Egorov ◽  
S.I. Egorova ◽  
G.F. Lemeshko
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Structural Changes ◽  
Structural Characteristics ◽  
Average Particle Size ◽  
Coherent Scattering ◽  
Milling Process ◽  
Average Particle ◽  
Ferrite Powder ◽  
Great Decrease

Problem of obtaining fine powders of strontium hexa-ferrite is actual because of its wide applications. The paper provides the results of studies of particle size distribution and structural characteristic changes of strontium hexa-ferrite powder (SrFe12O19) during milling in impact mill and after its consequent annealing. Mechanical processing of coarse particulate system was carried out in the mill for 120 minutes without electromagnetic effect and with creation of magneto fluidized bed, formed by perpendicular constant and alternating magnetic field with induction gradient of 210 mT/m, providing reciprocating motion of particles and aggregates with sizes of 3 – 4 mm. It was shown that milling of coarse strontium hexa-ferrite with average particle size 1558.5 μm and the most possible size 1500 μm in magneto fluidized bed allowed to intensify milling process and to provide a significant increase of powder particle sizes uniformity. It was found out, that milling in magneto fluidized bed leads to a great decrease of coherent scattering regions sizes and an increase of lattice micro-deformations and relative dislocation density. Consequent annealing of the powder for 2 hours at 850°C refined structural characteristics significantly. The carried out research allows to choose the optimal milling duration for solution of practical problems of powder metallurgy.

NIMROD 617KS

Alloy Digest ◽  
2002 ◽  
Vol 51 (5) ◽  
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Weld Metal ◽  
Tensile Properties ◽  
Base Metal ◽  
Heat Treating ◽  
Nominal Composition

Abstract Nimrod 617KS is an Inconel-type consumable with a nominal composition of nickel, 24% Cr,12% Co, and 9% Mo and is used to join UNS N06617 and Nicrofer 6023 to themselves. The alloy is designed for high-temperature service and is often used as the weld metal in dissimilar cases to ensure the weld is as strong as the base metal. This datasheet provides information on composition, hardness, and tensile properties as well as fracture toughness. It also includes information on heat treating and joining. Filing Code: Ni-583. Producer or source: Metrode Products Ltd.

COLUMBIUM 15W-5Mo-1Zr

Alloy Digest ◽  
1969 ◽  
Vol 18 (12) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Structural Properties ◽  
Base Alloy ◽  
Heat Treating ◽  
Temperature Performance

Abstract Columbium 15W-5 Mo- 1Zr is a columbium-base alloy capable of retaining usuable structural properties up to 2500 F. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as forming, heat treating, machining, and joining. Filing Code: Cb-17. Producer or source: Fansteel Metallurgical Corporation.

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