scholarly journals Effects of Solidification Pressure and Heat Treatment on the Microstructure and Micro-Hardness of AlSi9CuMg Alloy

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2229
Author(s):  
Lijun Wei ◽  
Baoshuai Han ◽  
Fan Ye ◽  
Yanjin Xu ◽  
Sujun Wu
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
High Pressure ◽  
Early Stage ◽  
Micro Hardness ◽  
Transmission Electron ◽  
Ageing Processes ◽  
Hardness Change ◽  
Solidification Pressure ◽  
Peak Value

The effect of high pressure (135 MPa) and the following heat treatment on the microstructure and micro-hardness of the squeezing cast AlSi9CuMg alloy is investigated, using optical microscopy (OM), Vickers tester, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicate that the application of high pressure can increase under-cooling and the cooling rate during solidification and cause the refinement of the microstructure. The enhanced melt flow resulting from high pressure can also break the dendrite to form the spherical and elliptical primary α (Al) grains during the early stage of solidification. The winter-sweet flower-shaped primary α (Al) phases can also be formed through plastic deformation caused by the flow of the partially solidified melt. The ageing treatment results showed that a maximum (peak) micro-hardness value was obtained for each of the three ageing temperatures at different ageing times, and the highest peak value was achieved at 175 °C for 480 min. The micro-hardness change of the sample under different ageing processes was attributed to the variation of type, density, and size of the precipitates.

Influence of Ageing Heat Treatment on Microstructure and Mechanical Properties of a Secondary Rheocast AlSi9Cu3(Fe) Alloy

2015 ◽  
Vol 828-829 ◽  
pp. 212-218 ◽  
Author(s):  
Stefano Capuzzi ◽  
Giulio Timelli ◽  
Alberto Fabrizi ◽  
Franco Bonollo
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Heat Treatment ◽  
Optical Microscope ◽  
Micro Hardness ◽  
Hardness Testing ◽  
Microscopy Technique ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Al Matrix

The effects of different process parameters (temperature and time) during the ageing treatment on the microstructure and the mechanical properties of a secondary rheocast AlSi9Cu3(Fe) alloy have been examined. Optical microscope investigations have been performed to qualitatively study the microstructure of the as-rheocast and thermal treated alloys. Transmission electron microscopy technique and selected area electron diffraction analyses have been used to characterize the hardening phases precipitated in the Al-matrix during the different ageing stages. The evolution of mechanical properties of the Al matrix has been monitored by micro-hardness testing.

The orientation relationships of nanobelt-like Si2Hf precipitates in an Al–Si–Mg–Hf alloy

2016 ◽  
Vol 49 (4) ◽  
pp. 1223-1230 ◽  
Author(s):  
Xueli Wang ◽  
Huilan Huang ◽  
Xinfu Gu ◽  
Yanjun Li ◽  
Zhihong Jia ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Coincident Site Lattice ◽  
Orthorhombic Structure ◽  
Orientation Relationships ◽  
Lattice Distribution ◽  
Site Lattice ◽  
Transmission Electron ◽  
Habit Planes ◽  
Al Matrix

The orientation relationships (ORs) between the Al matrix and Si2Hf precipitates with an orthorhombic structure in an Al–Si–Mg–Hf alloy after heat treatment at 833 K for 20 h were investigated by transmission electron microscopy and electron diffraction. Four ORs are identified as (100)Al||(010)p, (0\overline {1}1)Al||(101)pand [011]Al||[\overline {1}01]p; (11\overline {1})Al||(010)pand [011]Al||[\overline {1}01]p; (12\overline {1})Al||(010)p, (101)Al||(100)pand [1\overline {11}]Al||[001]p; (\overline {11}1)Al||(010)pand [112]Al||[\overline {1}01]p. The habit planes of these four ORs are rationalized by the fraction of good atomic matching sites at the interface. In addition, the formation of Si2Hf precipitates with a nanobelt-like morphology is interpreted on the basis of the near-coincident site lattice distribution.

Study of Corrosion Behavior of Conventional and Nanostructured WC-Co HVOF Sprayed Coats

2010 ◽  
Vol 64 ◽  
pp. 13-18 ◽  
Author(s):  
Shahin Khameneh Asl ◽  
Mohammad Reza Saghi Beyragh ◽  
Mahdi Ghassemi Kakroudi
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Heat Treating ◽  
Crystalline Phases ◽  
Chemical Test ◽  
Transmission Electron ◽  
Hvof Spray ◽  
Wear And Corrosion Resistance

Interest in nanomaterials has increased in recent years. This is due to the potential of size reduction to nanometric scale to provide properties of materials such as hardness, toughness, wear, and corrosion resistance. The current study is focused on WC-Co cermet coats, materials that are extensively used in applications requiring wear resistance. In this work, WC-17Co powder was thermally sprayed onto mild steel using High Velocity Oxy Fuel (HVOF) spray technique. The nanostructured specimen was produced from sprayed sample by heat-treating at 1100°C in a vacuum chamber. Their structures were studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Polarization and electrochemical impedance spectroscopy (EIS) tests were performed on the both types of coated samples in 3.5% NaCl solution. The amorphous phase in WC-17Co coating was transformed to crystalline phases by heat treatment at high temperatures. The heat treatment of these coatings at high temperature also resulted in partially dissolution of WC particles and formation of new crystalline phases. Generation of these phases produced the nanostructured coating with better mechanical properties. Comparative electro chemical test results showed that, the heat treatment could improve corrosion resistance of the nanostructured WC-17Co coat than the as sprayed coats.

Microstructural Studies of High Coercivity Nd15Fe77B8 Sintered Magnets

1987 ◽  
Vol 96 ◽  
Author(s):  
M. H. Ghandehari ◽  
J. Fidler
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Electron Microprobe ◽  
Boundary Phase ◽  
High Coercivity ◽  
Transmission Electron ◽  
Microstructural Studies ◽  
Domain Reversal

ABSTRACTMicrostructures of Nd15−xDyxFe77B8 prepared by alloying with Dy, and by using Dy2O3 as a sinl'ken adidive, have been determined using electron microprobe and transmission electron microscopy. The results have shown a higher Dy concentration near the grain boundaries of the 2–14–1 phase for magnets doped with Dy2O 3, as compared to the Dy-alloyed magnets. A two-step post sintering heat treatment was also studied for the two systems. The resultant concentration gradient of Dy in the 2–14–1 phase of the oxide-doped magnets is explained by the reaction of Dy2O3 with the Nd-rich grain boundary phase and its slow diffusion into thg 4–14–1 phase. Increased Dy concentration near the grain boundary is more effective in improving the coercivity, as domain reversal nucleation originates at or near this region.

Metallurgical Analysis of a Hopewell Copper Earspool

1971 ◽  
Vol 36 (3) ◽  
pp. 358-361 ◽  
Author(s):  
Arlene L. Fraikor ◽  
James J. Hester ◽  
Frederick J. Fraikor
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cold Working ◽  
Analytical Techniques ◽  
Fabrication Process ◽  
Micro Hardness ◽  
Transmission Electron ◽  
Metallurgical Analysis

AbstractA prehistoric Hopewell copper earspool was analyzed by a number of metallurgical techniques including transmission electron microscopy. While optical photomicrographs and micro-hardness data suggest that the final fabrication process was annealing, transmission electron microscopy indicates that some final cold working was applied. This paper illustrates a new application of physical analytical techniques to archaeology.

Microstructures and Growth Characteristics of Self-Assembled InAs/GaAs Quantum Dots Investigated by Transmission Electron Microscopy

2007 ◽  
Vol 26-28 ◽  
pp. 1207-1210
Author(s):  
Hyung Seok Kim ◽  
Ju Hyung Suh ◽  
Chan Gyung Park ◽  
Sang Jun Lee ◽  
Sam Kyu Noh ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Chemical Potential ◽  
Early Stage ◽  
Compressive Strain ◽  
Potential Gradient ◽  
Growth Direction ◽  
Transmission Electron ◽  
Self Assembled

The microstructure and strain characteristics of self-assembled InAs/GaAs quantum dots (QDs) were studied by using transmission electron microscopy. Compressive strain was induced to uncapped QDs from GaAs substrate and the misfit strain largely increased after the deposition of GaAs cap layer. Tensile strain outside QD was extended along the vertical growth direction; up to 15 nm above the wetting layer. Vertically nonaligned and aligned stacked QDs were grown by adjusting the thickness of GaAs spacer layers. The QDs with a lens-shaped morphology were formed in the early stage of growth, and their apex was flattened by the out-diffusion of In atoms upon GaAs capping. However, aligned QDs maintained their lens-shaped structure with round apex after capping. It is believed that their apex did not flatten because the chemical potential gradient of In was relatively low due to the adjacent InAs QD layers.

The effect of grain size on microstructure and stress relaxation in polycrystalline Y1Ba2Cu3O7−δ

1989 ◽  
Vol 4 (2) ◽  
pp. 248-256 ◽  
Author(s):  
T. M. Shaw ◽  
S. L. Shinde ◽  
D. Dimos ◽  
R. F. Cook ◽  
P. R. Duncombe ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Stress Relaxation ◽  
Optical Microscopy ◽  
Slow Cooling ◽  
Hierarchical Arrangement ◽  
Transmission Electron ◽  
Processing Variables

We have used transmission electron microscopy and optical microscopy to examine the effect that grain size and heat treatment have on twinning and microcracking in polycrystalline Y1Ba2Cu3O7−δ. It is shown that isothermal oxygenation heat treatments produce twin structures consisting of parallel twins, with a characteristic spacing that increases with increasing grain size. Slow cooling through the temperature range where the orthorhombic-to-tetragonal transformation induces twinning, however, produces a structure consisting of a hierarchical arrangement of intersecting twins, the scale of which appears to be independent of grain size. It is also shown that the microcracking induced by anisotropic changes in grain dimensions on cooling or during oxygenation can be suppressed if the grain size of the material is kept below about 1 μm. The results are examined in the light of current models for transformation twinning and microcracking and the models used to access the effect other processing variables such as oxygen content, doping or heat treatment may have on the microstructure of Y1Ba2Cu3O7−δ.

Dynamic Compaction of Al Alloys

1983 ◽  
Vol 28 ◽  
Author(s):  
J.W. Sears ◽  
B.C. Muddle ◽  
H.L. Fraser
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Al Alloys ◽  
Dynamic Compaction ◽  
Al Alloy ◽  
Analytical Transmission Electron Microscopy ◽  
Projectile Velocity ◽  
Transmission Electron

ABSTRACTPowders of Al alloy 7091 have been consolidated by means of dynamic compaction. The dependence of density and hardness on projectile velocity has been determined. The resulting as-compacted material has been characterized using analytical transmission electron microscopy and evidence of interparticle melting observed. The microstructural responseof the compacted material to heat treatment at 523 and 723°K has been investigated.

Novel Methods for Preparation and Surface Treatment of Nano-CaCO3

2013 ◽  
Vol 750-752 ◽  
pp. 336-339
Author(s):  
Fa Chao Wu ◽  
Teng Fei Shen
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Particle Size ◽  
Fourier Transform ◽  
Room Temperature ◽  
Transmission Electron ◽  
Reduce Energy Consumption ◽  
Scanning Electron

In this work, CaCO3 nanoparticles have been synthesized via heat-treatment of a new precursor. Effect of calcinations temperature on particle size has been investigated. The products were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). nanoCaCO3 was modified using chloroform as solvent and fatty acid as modifier atroom temperature. The advantage of this modification is that it can be proceed at room temperature and it can reduce energy consumption.

Synthesis and Characterization of Bioactive Sodium Titanate Nanotube by Alkali Hydrothermal Treatment

2007 ◽  
Vol 124-126 ◽  
pp. 1277-1280
Author(s):  
Yun Jong Kim ◽  
Sang Bae Kim ◽  
Keon Joon Cho ◽  
Taik Nam Kim ◽  
S.B. Cho
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Surface Treatment ◽  
Hydrothermal Treatment ◽  
Alkali Treatment ◽  
Sodium Titanate ◽  
Titanate Nanotube ◽  
Transmission Electron ◽  
Biocompatibility Test ◽  
Sodium Titanate Nanotube

In the present work, surface treatment of surgical implant Titanium alloy with micro bioactive nanotube was experimented. Surface treatment of Ti-6Al-4V bio-implant carried out by giving alkali hydrothermal and heat treatment. The specimens were treated in 1M NaOH at 100, 150, 200°C for different holding time of 2 hr, 4 hr, 6hr, 12 hr, 24hr & 48 hr. The hydrogel layer generated during the alkali treatment was crystallized to sodium titanate (Na2Ti6O13) and resulted into the formation of nano sized tubes on heat treatment. X-ray Diffractrometry (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) revealed the different phases and surface morphology of these nanorods. The biocompatibility test done using Simulate Body Fluid (SBF) showed that the Hydroxyapatite (HAp) was well formed at the sodium titanate nanotube layer generated on the Ti-6Al-4V specimen. The best condition for this increase in surface biocompatibility was optimized to 6 hours hydrothermal treatment under 200°C using 1 M NaOH followed by 1 hour heat treatment at 600°C.

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