Microstructural Design of Si3N4 Based Ceramics

1992 ◽  
Vol 287 ◽  
Author(s):  
M.J. Hoffmann ◽  
G. Petzow
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Microstructural Analysis ◽  
Coarse Grained ◽  
Boundary Phase ◽  
Microstructural Development ◽  
High Temperature Strength ◽  
Secondary Phases ◽  
The Matrix ◽  
High Degree

ABSTRACTParameters controlling the size and aspect ratio of elongated Si3N4 grains are discussed, based on the assumption that only pre-existing β-Si3N4 particles of the starting powder grow. Powder mixtures of α-rich and β-rich Si3N4 were prepared In order to study the microstructural development. The resulting microstructures were analyzed by quantitative microstructural analysis determining the distribution of the length and aspect ratio of the Si3N4 grains. Subsequently, the Influence of the sintering conditions on grain growth was analyzed In relation to mechanical properties. A high Weibull modulus and the non-catastrophic failure during thermal shock of coarse-grained materials Is attributed to an R-curve behaviour. Finally, the influence of sintering additives on the mechanical properties was studied. The Importance of phase relationships between the matrix and the grain boundary phase Is discussed for Si3N4 with Yb2O3 additives. It Is demonstrated that the oxygen content of Si3N4 powder must been taken Into account In order to devitrify defined secondary phases and to achieve a high degree of crystallization. A reduction in the amount of additives does not necessarily Improve the properties as high temperature strength and creep data Indicate.

scholarly journals Microstructural analysis of Al6063/sic with calcium additives for hardness enhancement

2018 ◽  
Vol 225 ◽  
pp. 03007
Author(s):  
Balaji Bakthavatchalam ◽  
Khairul Habib ◽  
Namdev Patil ◽  
Omar A Hussein
Keyword(s):  
Mechanical Properties ◽  
Silicon Carbide ◽  
Matrix Material ◽  
Microstructural Analysis ◽  
Wear Loss ◽  
Alloying Element ◽  
Silicon Phase ◽  
High Durability ◽  
The Matrix ◽  
Al6063 Alloy

Microstructural Analysis plays an important role in enhancing the mechanical properties of metals and composites. Usually Aluminium Silicon Carbide (Al6063/SiC) alloys are mixed with strontium, sodium and antimony for high durability even though they are toxic and costly. As an alternative calcium is used as an alloying element to improve the mechanical property of Al6063/Sic alloy. In this paper Al6063 is chosen as the matrix material while Sic is used as a reinforcement where calcium powder is added to modify the silicon phase of the composite. Finally, concentration of Silicon carbide is varied from 0 to 150 mg to produce four specimens of Al6063 alloy and it is subjected to microstructure analysis which showed the reduction of grain size and therefore improvement in the hardness from 52.9 HV to 58.4 HV and decrease in the wear loss from 3.97 to 3.27 percentage.

scholarly journals Efficient Hydrophobic Modification of Old Newspaper and Its Application in Paper Fiber Reinforced Composites

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 842 ◽  
Author(s):  
Weiwei Zhang ◽  
Jin Gu ◽  
Dengyun Tu ◽  
Litao Guan ◽  
Chuanshuang Hu
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Natural Fiber ◽  
Fiber Reinforced Composites ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Oh Groups ◽  
Uniform Dispersion ◽  
The Matrix ◽  
Paper Fibers

Paper fibers have gained broad attention in natural fiber reinforced composites in recent years. The specific problem in preparing paper fiber reinforced composites is that paper fibers easily become flocculent after pulverization, which increases difficulties during melt-compounding with polymer matrix and results in non-uniform dispersion of paper fibers in the matrix. In this study, old newspaper (ONP) was treated with a low dosage of gaseous methyltrichlorosilane (MTCS) to solve the flocculation. The modified ONP fibers were characterized by Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Thermogravimetric Analysis (TG). Then the modified ONP fibers and high-density polyethylene (HDPE) were extruded and pelletized to prepare ONP/HDPE composites via injection molding. Maleic anhydride-grafted polyethylene (MAPE) was added to enhance the interfacial bonding performance with the ultimate purpose of improving the mechanical strength of the composites. The mechanical properties such as tensile, flexural, and impact strength and the water absorption properties of the composite were tested. The results showed that the formation of hydrogen bonding between ONP fibers was effectively prevented after MTCS treatment due to the reduction of exposed –OH groups at the fiber surface. Excessive dosage of MTCS led to severe fiber degradation and dramatically reduced the aspect ratio of ONP fibers. Composites prepared with ONP fibers modified with 4% (v/w) MTCS showed the best mechanical properties due to reduced polarity between the fibers and the matrix, and the relatively long aspect ratio of treated ONP fibers. The composite with or without MAPE showed satisfactory water resistance properties. MTCS was proven to be a cheap and efficient way to pretreat old newspaper for preparing paper fiber reinforced composites.

Optimalization of Tempering Temperature of 9CrNB Steel in Železiarne Podbrezová Steelworks

2017 ◽  
Vol 891 ◽  
pp. 137-142 ◽  
Author(s):  
Ľudovít Parilák ◽  
Pavel Bekeč ◽  
Lucia Domovcová ◽  
Pavol Beraxa ◽  
Milan Mojžiš ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Microstructural Analysis ◽  
Theoretical Studies ◽  
Secondary Phases ◽  
Tempering Temperature ◽  
Carbide Phases ◽  
Hot Rolled ◽  
Martensite Microstructure ◽  
Very High

This paper deals with the optimalization of tempering temperature of 9CrNB steel in Železiarne Podbrezová Steelworks, where hot-rolled tubes were produced with dimensions of 88.9 x 12.51 mm. Austenitising at 1070°C/12m/hr was carried out after rolling, and samples were subsequently tempered at 790°C, 760°C and 720°C/4m/hr. The results of testing the mechanical properties show that only tempering at 790°C fulfilled all of the mechanical properties requirements (Rp0,2, Rm, A5, HBW, KV2). The mechanical properties of grade P92 were used for comparison with 9CrNB mechanical properties, according to the relevant standard of STN EN 10216-2+A2. Yield strength requirements (Rp0,2) were also fulfilled in the temperature range from 100 to 600 °C. Microstructural analysis showed that tempering at 720°C, and also at 760°C does not lead to the complete tempering of martensite microstructure. We observed segregation of secondary phases at the grain boundary, but cementite films between individual laths did not coagulate to form carbide phases. By tempering at 790°C the intensity of formation of carbide phases, coagulation and growth of carbide phases is very high and leads to disintegration of laths. Despite satisfactory results, theoretical studies with respect to the selected chemical composition of 9CrNB steel show that to achieve sufficient dissolution of carbide or nitride phases (especially BN), it is necessary to use high temperature austenitization up to about 1200°C, followed by tempering below Ac1.

scholarly journals Reaction Layer Analysis of In Situ Reinforced Titanium Composites: Influence of the Starting Material Composition on the Mechanical Properties

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 265
Author(s):  
Isabel Montealegre-Meléndez ◽  
Cristina Arévalo ◽  
Ana M. Beltrán ◽  
Michael Kitzmantel ◽  
Erich Neubauer ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Reaction Layer ◽  
Processing Parameters ◽  
Starting Material ◽  
Secondary Phases ◽  
Layer Analysis ◽  
The Matrix ◽  
B4c Particles ◽  
Al Powder

This study aims at the analysis of the reaction layer between titanium matrices and reinforcements: B4C particles and/or intermetallic TixAly. Likewise, the importance of these reactions was observed; this was particularly noteworthy as regard coherence with the obtained results and the parameters tested. Accordingly, five starting material compositions were studied under identical processing parameters via inductive hot pressing at 1100 °C for 5 min in vacuum conditions. The results revealed how the intermetallics limited the formation of secondary phases (TiC and TiB) created from the B and C source. In this respect, the percentages of TiB and TiC slightly varied when the intermetallic was included in the matrix as prealloyed particles. On the contrary, if the intermetallics appeared in situ by the addition of Ti-Al powder in the starting blend, their content was lesser. The mechanical properties values and the tribology behaviour might deviate, depending on the percentage of the secondary phases formed and its distribution in the matrix.

Numerical and Experimental Investigation on Hot Backward Extrusion Process of Mg-Gd-Y-Zn-Zr Magnesium Alloy

2014 ◽  
Vol 788 ◽  
pp. 127-133 ◽  
Author(s):  
Zhi Wen Shao ◽  
Xiu Rong Zhu ◽  
Jun Wang ◽  
Rong Wang ◽  
Yong Dong Xu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloy ◽  
Hot Extrusion ◽  
Element Model ◽  
Extrusion Process ◽  
Tensile Yield Strength ◽  
Secondary Phases ◽  
Rigid Plastic ◽  
Backward Extrusion ◽  
The Matrix

The hot backward extrusion process of the Mg-Gd-Y-Zn-Zr magnesium alloy was investigated by both numerical simulation and experiments. An axisymmetric 2D rigid-plastic finite element model (FEM) was established to simulate the material flow during the extrusion process. The shapes of the dies were optimized in order to avoid severe stress concentration and obtain uniform deformation of the workpiece. After hot extrusion, the microstructures of the alloys were obviously refined, and the secondary phases which included many long-period stacking order (LPSO) phases precipitated in the matrix. The optimal comprehensive mechanical properties of the alloy have been obtained after extrusion and ageing at 200°C for 48h with the ultimate tensile strength of 434MPa, tensile yield strength of 375MPa and elongation of 4.5%, respectively. The good mechanical properties were mainly attributed to the fine microstructures and numerous precipitates in the matrix.

On the crystallography of triple points in nonoxide ceramics: epitaxial relationships are a function of statistics and geometry

1996 ◽  
Vol 54 ◽  
pp. 648-649
Author(s):  
Warren J. MoberlyChan
Keyword(s):  
High Temperature ◽  
Secondary Phase ◽  
Continuous Phase ◽  
Microstructural Development ◽  
High Temperature Strength ◽  
The Matrix ◽  
Critical Flaw ◽  
Superior Mechanical Properties ◽  
Triple Points ◽  
Nonoxide Ceramics

Covalent ceramics, such as SiC and Si3N4, can have superior mechanical properties for high temperature structural materials. However, densification difficulties and poor fracture toughness have hindered use. Traditionally, the choice of sintering additives has been a “hit and miss” method to improve properties. The primary purpose of an additive is to provide good density, as residual pore size relates to critical flaw size. Another feature of an additive has recently been to invoke fracture around the matrix grains, thereby enhancing toughness. Most reported nonoxide ceramics include upwards of 10% secondary phase(s) as a continuous phase between many matrix grains and causing poor high temperature strength. Even when this secondary phase is crystallized, thin amorphous interfaces are observed. The ABC-SiC processed for this study incorporates <5% total Al, B, and C as additions. The Al enhances densification, as well as the P-to-a phase transformation at lower temperatures (1600-1900°C); and controlling die microstructural development has provided record toughness.

Effect of Distance between Passes in Friction Stir Processing of Magnesium Alloy

2012 ◽  
Vol 585 ◽  
pp. 397-401 ◽  
Author(s):  
M. Govindaraju ◽  
K. Rao Prasad ◽  
Uday Chakkingal ◽  
K. Balasubramanian
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloy ◽  
Friction Stir Processing ◽  
Developmental Studies ◽  
Secondary Phases ◽  
Friction Stir ◽  
Processed Material ◽  
The Matrix ◽  
Cast Alloys ◽  
Tool Pin

Friction stir processing is applied for property improvement of cast alloys for last two decades and many developmental studies were carried out in this topic on various alloys. In the current work, friction stir processing was carried out on rare earth containing magnesium alloy AE42. This alloy was specially developed for automobile application as it has better creep resistance than commercial magnesium alloys. Multi-pass Friction Stir Processing was carried out with varying the distance between passes from 0.5 mm to 2.5 mm using 12 mm shoulder diameter tool. Pin was with conical (tapered) and flat configurations with 3 mm height. After processing, the resultant mechanical and metallurgical properties were evaluated. Microstructure was refined to 5 micron and the secondary phases were made in to tiny pieces of 0.5-1 micron and evenly distributed in the matrix. Continuous network of grain boundary which is reason for poor mechanical properties was eliminated. Mechanical properties were improved by 30%. The variation of mechanical properties of processed material with respect to variation of distance between passes was negligible from 1 mm to 1.5 mm for flat pin tool.

scholarly journals The influence of microstructure on mechanical properties of 3D printable geopolymer composites

2020 ◽  
Vol 322 ◽  
pp. 01011
Author(s):  
Kinga Korniejenko ◽  
Krzysztof Miernik ◽  
Wei-Ting Lin ◽  
Arnaud Castel
Keyword(s):  
Mechanical Properties ◽  
Microstructural Analysis ◽  
Ceramic Materials ◽  
Production Method ◽  
Industrial Sector ◽  
Sem Analysis ◽  
Raw Material ◽  
Material Structure ◽  
The Matrix ◽  
Manufacturing Technologies

The additive manufacturing technologies are fast-developing industrial sector and, potentially, a ground-breaking technology. They have many advantages such as the saving of resources and energy efficiency. However, the full exploitation of 3D printing technology for ceramic materials is currently limited; a lot of research is being conducted in this area. A promising solution seems to be geopolymers, but its application requires a better understanding of the behaviour this group of materials. This article analyses the influence of microstructure on mechanical properties whilst taking the production method into consideration. The paper is based on comparative analysis – the investigation is focused on the influence of material structure on the mechanical properties and fracture mechanism of these kinds of composites, including those reinforced with different kind of fibres. As a raw material for the matrix, fly ash from the Skawina coal power plant (located in: Skawina, Lesser Poland, Poland) was used. The investigation was made by SEM analysis. The results show that the microstructural analysis did not sufficiently explain the underlying reasons for the observed differences in the mechanical properties of the composites.

The Rewari meteorite

1979 ◽  
Vol 43 (327) ◽  
pp. 423-427
Author(s):  
S. P. Das Gupta ◽  
P. R. Sen Gupta ◽  
N. R. Sen Gupta ◽  
D. R. Das Gupta ◽  
A. Dube
Keyword(s):  
Chemical Analysis ◽  
Coarse Grained ◽  
Alteration Zone ◽  
Fragment Composition ◽  
Coarse Texture ◽  
The Matrix ◽  
Wet Chemical ◽  
High Degree ◽  
Lower Oxidation ◽  
Cut Surface

SummaryThe meteorite was an oriented polyhedron, which broke up into at least two parts after entry into the Earth's atmosphere. It has undergone some degree of terrestrial weathering. A cut surface of the meteorite shows light-grey interior with sporadic rusty-brown patches and a distinct brown alteration zone close to the fusion crust. Weathering has resulted in preferential replacement of NiFe by limonite, and veining of minerals by goethite.Rewari is an equilibrated chondrite with rare ghosts of chondrules and at least one lithic fragment. Composition of olivine, as indicated by microprobe analysis is Fa23, which agrees well with bulk wet chemical analysis; that indicated by d130 is Fa18–20. From the outer surface inwards, four petrographic zones can be distinguished in the meteorite: a skin, about 0.01 mm thick, a troilite-poor zone slightly thicker than the skin, a troilite-rich ‘soaking zone’, about 0.5–0.6 mm thick, and a relatively coarse-grained interior. These are described in detail.The interior of the meteorite is composed of relatively coarse-grained crystalline silicates with disseminated metallic minerals including plessitic and zoned inter-growths of kamacite and taenite. The matrix shows a high degree of integration with the chondrules. The coarse texture and zonation of taenite may be the result of protracted heat treatment responsible for recrystallization. The constituent grains show considerable shock effects such as fracturing, comminution, veins of shock-melted pseudotachylite, pressure twinning, and undulose extinction. Chemical composition (mean of two wet chemical analysis) of the meteorite is: metallic Fe 7.475, Ni 0.975, Co 0.045; as sulphide Fe 3.200, Ni 0.090, Co < 0.01; SiO2 38.060, TiO2 0.10, Al2O3 2.34, Fe2O3 0.175, Cr2O3 0.485, FeO 13.950, MnO 0.210, NiO trace, CaO 1.875, MgO 26.265, Na2O 0.89, K2O 0.115, P2O5 0.285, H2O− 0.295, H2O+ 0.81, CO2 trace, S (total) 1.890, C (total) 0.19 per cent. The chemistry, mineralogy, and texture show that the Rewari meteorite is an L6 chondrite. Compared to average L-group chondrite it has a higher content of MgO and lower of SiO2, a little lower oxidation state, and tends to be enriched in siderophilic elements.

PHASE-FIELD SIMULATION FOR MICROSTRUCTURAL DEVELOPMENT OF TEXTURED CERAMICS PREPARED BY REACTION TEMPLATED GRAIN GROWTH

2012 ◽  
Vol 02 (01) ◽  
pp. 1250009 ◽  
Author(s):  
LIANGLIANG LIU ◽  
FENG GAO ◽  
GUOXIN HU ◽  
JIANGNAN LIU
Keyword(s):  
Aspect Ratio ◽  
Grain Growth ◽  
Phase Field ◽  
Size Fraction ◽  
Phase Field Method ◽  
Microstructural Development ◽  
Templated Grain Growth ◽  
Textured Ceramics ◽  
The Matrix ◽  
Simulation Results

A modified model using phase-field method in order to describe the microstructural development for the reaction templated grain growth process was developed. The current model well expressed anisotropic enlargement of the template particles. The initial parameters such as the matrix particles size, the template particles size, fraction, aspect ratio of the template particles and porosity were examined. The simulation results show that the fraction of oriented grains increases with decreasing the matrix particles size and porosity, and increasing the fraction of the initial template particles. An increase for the aspect ratio of template particles gives rise to the anisotropic microstructure development. The study suggests that the simulation results would give a guiding principle in terms of the initial preparation conditions for the textured ceramics having both a large fraction of oriented grains and anisotropic microstructure.

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