scholarly journals Synthesis of Nanocrystalline AZ91 Magnesium Alloy Dispersed with 15 vol.% Submicron SiC Particles by Mechanical Milling

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 901
Author(s):  
Shitian Su ◽  
Jixue Zhou ◽  
Shouqiu Tang ◽  
Huan Yu ◽  
Qian Su ◽  
...  
Keyword(s):  
Mechanical Milling ◽  
Sem Analysis ◽  
Submicron Particles ◽  
X Ray Diffraction ◽  
Az91 Magnesium Alloy ◽  
Magnesium Matrix ◽  
Pinning Effect ◽  
Sic Particles ◽  
Transmission Electron ◽  
Az91 Magnesium

The development of a magnesium matrix composite with a high content of dispersions using conventional liquid-phase process is a great challenge, especially for nanometer/submicron particles. In this work, mechanical milling was employed to prepare nanocrystalline AZ91 dispersed with 15 vol.% submicron SiC particles (SiCp/AZ91). AZ91 with no SiCp was applied as a comparative study with the same mechanical milling. In order to investigate the mechanism of dispersing, the morphology evolution of powders and the corresponding SiCp distribution were observed. As the scanning electron microscope (SEM) analysis exhibited, the addition of SiCp accelerated the smashing of AZ91 particles, which promoted the dispersion of SiCp in AZ91. Thus, after mechanical milling, 15 vol.% SiCp, which was smashed from 800 to 255 nm, got uniformly distributed in the Mg matrix. Based on X-ray diffraction (XRD) results, part of the Mg17Al12 precipitate got dissolved, and an Al-supersaturated Mg solid solution was formed. The transmission electron microscopy (TEM) results showed that the ultimate Mg grain (32 nm) of milled SiCp/AZ91 was much smaller than that of milled AZ91 (64 nm), which can be attributed to a pinning effect of submicron SiCp. After mechanical milling, the hardness of SiCp/AZ91 reached 185 HV, which was 185% higher than the original AZ91 and 33% higher than milled AZ91, due to fine Mg grain and submicron dispersions.

Microstructure and Mechanical Property in Cast AZ91 Magnesium Alloy with Y Addition

2014 ◽  
Vol 783-786 ◽  
pp. 472-477 ◽  
Author(s):  
Tatsuaki Sakamoto ◽  
Shu Chen Sun ◽  
Takuya Matsumoto ◽  
Kiyomichi Nakai ◽  
Sengo Kobayashi ◽  
...  
Keyword(s):  
Vickers Microhardness ◽  
Primary Dendrite ◽  
Nucleation Site ◽  
X Ray Diffraction ◽  
Az91 Magnesium Alloy ◽  
Optical Scanning ◽  
Transmission Electron ◽  
Az91 Magnesium ◽  
Electron Microscopes ◽  
Non Equilibrium

Microstructures and Vickers microhardness in AZ91 magnesium alloys without and with 1mass%Y addition fabricated by casting were investigated. Vickers microhardness increases with adding 1%Y. Microstructure in AZ91 without Y addition was analyzed to contain mainly α-Mg and Mg17Al12by X-ray diffraction. Microstructural observations with optical, scanning and transmission electron microscopes show that microstructure consists of α-Mg dendrite, non-equilibrium eutectic Mg17Al12and lamellar Mg17Al12. The non-equilibrium eutectic Mg17Al12exists between α-Mg dendrites. The lamellar Mg17Al12forms near the edge of the α-Mg dendrite arm. The lamellar Mg17Al12has Burgers orientation relationship for α-Mg matrix. It suggests that the lamellar Mg17Al12precipitates from Al-supersaturated region within α-Mg dendrite. Addition of Y to AZ91 hardly changes dendrite arm spacing, but decreases a size of region, where longitudinal directions of primary dendrite arms are almost parallel or a single dendrite exists. Y-addition increases nucleation site for dendrite, namely makes the unidirectionally-solidified region fine, resulting in increase in hardness.

scholarly journals Study of the Microstructure and Ring Element Segregation Zone of Spray Deposited SiCp/7055Al

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1299 ◽  
Author(s):  
Hao Yang ◽  
Xin-wei She ◽  
Bin-bin Tang ◽  
Chun-mei Li ◽  
Xian-quan Jiang
Keyword(s):  
Volume Fraction ◽  
Spray Deposition ◽  
Optical Microscope ◽  
Matrix Composites ◽  
Pinning Effect ◽  
Sic Particles ◽  
Transmission Electron ◽  
Al Matrix Composites ◽  
Element Enrichment ◽  
Al Matrix

Composites of 7055 aluminum (Al) matrix reinforced with SiC particles were prepared using the spray deposition method. The volume fraction of the phase reinforced with SiC particles was 17%. The effect of the introduction of SiC particles on the deposited microstructure and properties of the composites was studied in order to facilitate the follow-up study. The structure and element enrichment zone of spray-deposited SiCp/7055 Al matrix composites were studied by Optical Microscope (OM), X-ray diffraction (XRD), Scanning Electronic Microscopy (SEM) and Transmission electron microscopy (TEM). The results show that the reinforcement phases of the SiC particles were uniformly distributed on the macro and micro levels, and a few SiC particles were segregated into annular closed regions. C and Si on the surface of SiC particles diffused to the Al matrix. The distribution of the two elements was gradient weakening with SiC particles as the center, and the enrichment zones of Si, Mg and Cu formed in the middle of the closed annular area of a few SiC particles. The enrichment zones were mainly composed of alpha-Al, SiC, Al2CuMg, Al2Cu and MgZn2. AlCu and AlMgCu phase precipitate on the surface of the SiC particles, beside the particle boundary, and had the characteristics of preferred nucleation. They tended to grow at the edges and corners of SiC particles. It was observed that the formation of nanoparticles in the alloy had a pinning effect on dislocations. The different cooling rates of the SiC particles and the Al matrix led to different aluminum liquid particle sizes, ranging from 20 to 150 μm. In the region surrounded by SiC particles, the phenomenon of large particles extruding small particles was widespread. Tearing edges and cracks continued to propagate around the SiC particles, increasing their propagation journey and delaying the fracture of the materials.

Preparation of Y-Ti Bioxides Strengthened Fe-Cr Alloy by Mechanical Milling and Hot Pressing

2013 ◽  
Vol 475-476 ◽  
pp. 1307-1310
Author(s):  
Lei Dai ◽  
Ping Feng ◽  
Cai Hua Huang ◽  
Guang Wei Zhao
Keyword(s):  
Electron Microscope ◽  
Hot Pressing ◽  
Mechanical Milling ◽  
Milling Time ◽  
Operating Temperature ◽  
Oxide Dispersion Strengthened ◽  
X Ray Diffraction ◽  
Ferritic Alloys ◽  
X Ray ◽  
Transmission Electron

Oxide-dispersion-strengthened (ODS) ferritic alloys are fascinating materials for future fusion power reactors due to these materials would allow a substantial increase of the operating temperature. Y-Ti bioxides strengthened Fe-Cr alloy was produced by mechanical milling (MM) followed by hot pressing (HP). Microstructure changes of the mixed powders during mechanical milling and subsequent hot pressing were structurally characterized by means of scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The observations of structure of the mixed powders after MM indicated that the powders are fractured and welded with rotation and vibration of container during mechanical milling. And the particle size decreases with increasing milling time. Nanoscale Y-Ti bioxides were formed during the HP process.

scholarly journals Removal of benzotriazole by Photo-Fenton like process using nano zero-valent iron: response surface methodology with a Box-Behnken design

2017 ◽  
Vol 19 (1) ◽  
pp. 104-112 ◽  
Author(s):  
Mehdi Ahmadi ◽  
Kurosh Rahmani ◽  
Ayat Rahmani ◽  
Hasan Rahmani
Keyword(s):  
Response Surface Methodology ◽  
Electron Microscope ◽  
Response Surface ◽  
Sem Analysis ◽  
Zero Valent Iron ◽  
X Ray Diffraction ◽  
Box Behnken Design ◽  
Transmission Electron ◽  
Nano Zero Valent Iron ◽  
Good Agreement

Abstract In this paper, the removal of benzotriazole (BTA) was investigated by a Photo-Fenton process using nano zero valent iron (NZVI) and optimization by response surface methodology based on Box-Behnken method. Effect of operating parameters affecting removal efficiency such as H2O2, NZVI, and BTA concentrations as well as pH was studied. All the experiments were performed in the presence of ultraviolet radiation. Predicted levels and BTA removal were found to be in good agreement with the experimental levels (R2 = 0. 9500). The optimal parameters were determined at 60 min reaction time, 15 mg L-1 BTA, 0.10 g L-1 NZVI, and 1.5 mmol L-1 H2O2 for Photo-Fenton-like reaction. NZVI was characterized using X-ray diffraction (XRD), transmission electron microscope (TEM) images, and scanning electron microscope (SEM) analysis.

Mechanical and fracture properties of an AZ91 Magnesium alloy reinforced by Si and SiC particles

2009 ◽  
Vol 69 (13) ◽  
pp. 2256-2264 ◽  
Author(s):  
Z. Trojanová ◽  
V. Gärtnerová ◽  
A. Jäger ◽  
A. Námešný ◽  
M. Chalupová ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Az91 Magnesium Alloy ◽  
Fracture Properties ◽  
Sic Particles ◽  
Az91 Magnesium ◽  
Mechanical And Fracture Properties

Reduced electrical resistivity of reaction-sintered SiC by nitrogen doping

2008 ◽  
Vol 23 (4) ◽  
pp. 1020-1025 ◽  
Author(s):  
Young-Sam Jeon ◽  
Hyunho Shin ◽  
Young-Hyun Lee ◽  
Sang-Won Kang
Keyword(s):  
Heat Treatment ◽  
Electrical Resistivity ◽  
Photoelectron Spectroscopy ◽  
Nitrogen Doping ◽  
Nitrogen Atmosphere ◽  
X Ray Diffraction ◽  
Post Heat Treatment ◽  
X Ray ◽  
Sic Particles ◽  
Transmission Electron

A post heat treatment of reaction-sintered SiC at 1700 °C in nitrogen atmosphere significantly reduced electrical resistivity. A trace of insulating Si3N4 phase was detected via nitrogen heat treatment in high-resolution transmission electron microscopy observation; however, based on x-ray photoelectron spectroscopy, the evidence of nitrogen doping into SiC lattice has been claimed as the mechanism to the decreased resistivity. The increase of the total volume of SiC was apparent in x-ray diffraction during the nitrogen heat treatment, which was interpreted to stem from the growth of the nitrogen-doped intergranular SiC particles and surface doping of the primary SiC to reduce the contact resistance between the primary SiC particles.

Fullerene-Metal Composites: Phase Transformations During Milling and Sintering

2011 ◽  
Vol 172-174 ◽  
pp. 727-732 ◽  
Author(s):  
Ileana Irais Santana ◽  
Francisco Carlos Robles Hernandez ◽  
Vicente Garibay-Febles ◽  
Hector A. Calderon
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Phase Transformations ◽  
Mechanical Milling ◽  
X Ray Diffraction ◽  
Metal Composites ◽  
X Ray ◽  
Plasma Sintering ◽  
Transmission Electron ◽  
Spark Plasma

Composites of Fe-C60and Al C60produced by mechanical milling and sinterized by Spark Plasma Sintering are investigated with special attention to the mechanical properties of the products. The processing involves phase transformations of the fullerenes that are interesting to follow and characterize. This involves formation of tetragonal/rhombohedral diamond and carbides during sintering and milling. Transmission Electron Microscopy (TEM) and Raman Spectroscopy techniques are also used to confirm preliminary results of X Ray Diffraction (XRD) related to the formation of nanostructures i.e., grain size of the crystals during mechanical milling and after sintering, spatial distribution of phases and the different phases that are developed during processing.

Micro Arc Oxidation of AZ91 Magnesium Alloy – Effect of Organic Compounds in the Electrolyte

2014 ◽  
Vol 353 ◽  
pp. 217-222 ◽  
Author(s):  
Namik Kemal Gozuacik ◽  
Mert Altay ◽  
Murat Baydogan
Keyword(s):  
Corrosion Resistance ◽  
Coating Thickness ◽  
Electrochemical Corrosion ◽  
Organic Chemicals ◽  
X Ray Diffraction ◽  
Az91 Magnesium Alloy ◽  
Micro Arc Oxidation ◽  
Az91 Magnesium ◽  
Alloy Effect ◽  
Thickness Measurements

AZ91 Mg alloy was micro arc oxidized under constant electrical parameters in silicate based and phosphate based electrolytes with and without addition of organic chemicals, namely Hexamethylenetetramine (HMTA), TRIS (hydroxymethyl) aminomethane (THAM) and Glycerol in two different concentrations. Following oxidation, samples were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), coating thickness measurements, hardness measurements and electrochemical corrosion tests. Results showed that coating layers mainly consisted of MgO, Mg2SiO4 and MgF2 for silicate based electrolytes, and MgO for phosphate based electrolytes. Incorporation of organic chemicals into electrolyte composition did not change the type of the phases in the coating. However, when they are added in silicate based electrolytes, pore density and coating thickness are reduced and pore size is increased. On the other hand, there is no significant change in surface morphology when organic chemicals are added in phosphate based electrolyte. In the view point of corrosion resistance, organic chemicals did not enhance corrosion resistance of the samples oxidized in silicate based electrolytes, but exhibited some increment in corrosion resistance of the samples oxidized in phosphate based electrolytes.

Synthesis of nanostructured metal (Fe, Al)-C60 composites

2010 ◽  
Vol 1276 ◽  
Author(s):  
I. I. Santana García ◽  
V. Garibay Febles ◽  
H. A. Calderon
Keyword(s):  
Raman Spectroscopy ◽  
Mechanical Milling ◽  
Volume Fraction ◽  
High Volume ◽  
X Ray Diffraction ◽  
Nanostructured Composite ◽  
Plasma Sintering ◽  
Transmission Electron ◽  
Show Evidence ◽  
Spark Plasma

AbstractComposites of M-2.5 mol. % Fullerene C60 composites (where M= Fe or Al) are prepared by mechanical milling and Spark Plasma Sintering (SPS). The SPS technique has been used to consolidate the resulting powders and preserve the massive nanostructure. Results of X-Ray Diffraction and Raman Spectroscopy show that larger milling balls (9.6 mm in diameter) produce transformation of the fullerene phase during mechanical milling. Alternatively smaller milling balls (4.9 mm in diameter) allow retention of the fullerene phase. SEM shows homogeneous powders with different particle sizes depending on milling times. Sintering produces nanostructured composite materials with different reinforcing phases including C60 fullerenes, diamonds and metal carbides. The presence of each phase depends characteristically on the energy input during milling. Transmission Electron Microscopy (TEM) and Raman Spectroscopy show evidence of the spatial distribution and nature of phases. Diamonds and carbides can be identified for the sintered Fe containing composites with a relatively high volume fraction.

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