Microstructures and properties of large bulk solidified TiC–TiB2 composites prepared by combustion synthesis under high gravity

2009 ◽  
Vol 61 (3) ◽  
pp. 281-284 ◽  
Author(s):  
Zhongmin Zhao ◽  
Long Zhang ◽  
Yigang Song ◽  
Weiguo Wang ◽  
Hongbo Liu
Keyword(s):  
Combustion Synthesis ◽  
High Gravity ◽  
Large Bulk

Large Bulk Al2O3/ZrO2 (Y2O3) Nanocrystalline Composites Prepared by Combustion Synthesis under High Gravity

2010 ◽  
Vol 434-435 ◽  
pp. 9-12 ◽  
Author(s):  
Zhong Min Zhao ◽  
Long Zhang ◽  
Chuan Zeng Pan ◽  
Quan Yang ◽  
Zhen Sheng Qu ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Flexural Strength ◽  
Relative Density ◽  
Combustion Synthesis ◽  
High Gravity ◽  
Gravity Level ◽  
Nanocrystalline Composites ◽  
Large Bulk ◽  
The Matrix ◽  
High Gravity Field

The large bulk Al2O3/ZrO2 (Y2O3) eutectics were achieved by combustion synthesis in high-gravity field. With increasing high-gravity level, the matrix of eutectics transformed the rod-shaped colonies from the cellular ones, and the nanocrystalline microstructures came into existence as the high-gravity level was larger than 200g. The relative density, hardness, flexural strength and fracture toughness increased simultaneously with increasing high-gravity level, and reached the maximum values of 98.6%, 18.6GPa, 1248MPa and 15.6MPa•m1/2 respectively as the high-gravity level was 250g.

TiB2-(Ti,W)C Eutectic Composite Ceramics Prepared by Combustion Synthesis under High Gravity

2010 ◽  
Vol 177 ◽  
pp. 386-389 ◽  
Author(s):  
Xue Gang Huang ◽  
Long Zhang ◽  
Zhong Min Zhao ◽  
Chuan Zeng Pan ◽  
Guan Ling Su
Keyword(s):  
Combustion Synthesis ◽  
Lattice Structure ◽  
Mutual Solubility ◽  
Full Density ◽  
High Gravity ◽  
Composite Ceramics ◽  
Eutectic Composite ◽  
Immiscible Liquids ◽  
Large Bulk ◽  
High Gravity Field

Large bulk solidified TiC-TiB2 eutectic composite ceramics were prepared by combustion synthesis under high gravity, and the WO3 was introduced into the combustion synthesis as one of oxidants in thermit to obtain the Ti-W-Cr-C-B liquid, so near-full-density TiB2-(Ti,W)C eutectic composite ceramics without the macrocracks were achieved. The ceramic matrix was mainly composed of TiB2-(Ti,W)C eutectic microstructures, and a few of Al2O3 and Al2O3-ZrO2 eutectic structures were also detected in between Ti-W carbides. Due to the introduction of the high gravity field, Stocks immigration of the immiscible liquids took place due to their density differences, resulting in float-up of oxide liquid and settle-down of Ti-W-Cr-C-B liquid, and the layered melt consisting of oxide liquid and Ti-W-Cr-C-B liquid was formed, finally, TiB2-(Ti,W)C eutectic composite grown from the melt. Due to the mutual solubility of W-Ti, the W atom diffused into the TiC, leading to the formation of (Ti,W)C solid solution as same as crystal lattice structure of TiC. The relative density, Vickers hardness and fracture toughness of the composite ceramics measured 98.4%, 26.4 GPa and 7.6±0.5 MPa•m1/2, respectively.

Ultra-High-Hard Composites of TiC-TiB2 Prepared by Combustion Synthesis under High Gravity

2010 ◽  
Vol 434-435 ◽  
pp. 13-16 ◽  
Author(s):  
Zhen Sheng Qu ◽  
Quan Yang ◽  
Zhong Min Zhao ◽  
Long Zhang ◽  
Chuan Zeng Pan ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Gravity Field ◽  
Combustion Synthesis ◽  
High Hardness ◽  
High Strength ◽  
High Gravity ◽  
Rapid Separation ◽  
Large Bulk ◽  
High Gravity Field ◽  
Coupled Growth

The large-bulk solidified TiC-TiB2 composites were prepared by combustion synthesis in high-gravity field. XRD, FESEM, SEM and EDS results showed that TiC-TiB2 composites were mainly composed of TiC matrix in which a number of fine TiB2 platelets were embedded, surrounded by the boundary regions consisting of (Cr, Ti) C0.63 carbides. The hardness, flexural strength and fracture toughness of TiC-TiB2 composites measured 28.5GPa, 750±25MPa and 6.2±0.5MPa•m1/2. High hardness of the composites benefits from the absence of the intermediate borides and the achievement of stoichiometric TiC phases due to rapid solidification, whereas the achievement of high strength benefits the refinement and homogeneity of the microstructures due to rapid separation of liquid oxides in high-gravity field and rapid coupled growth of TiC and TiB2 phases.

Large-Bulk Solidified Al2O3-ZrO2(Y2O3) Prepared by Self-Pressure Assisting Combustion Synthesis under High Gravity

2010 ◽  
Vol 177 ◽  
pp. 394-397 ◽  
Author(s):  
Guan Ling Su ◽  
Zhong Min Zhao ◽  
Long Zhang ◽  
Xue Gang Huang ◽  
Chuan Zeng Pan
Keyword(s):  
Combustion Synthesis ◽  
Volume Fraction ◽  
High Gravity ◽  
Composite Ceramics ◽  
Pressure Force ◽  
Sem Images ◽  
Large Bulk ◽  
Α Al2o3 ◽  
Shrinkage Cavities ◽  
Spherical Crystals

By introducing self-pressure processing into combustion synthesis under high gravity, Al2O3-ZrO2(4Y) eutectic composite ceramics without shrinkage cavities and holes were achieved, and the self-pressure processing also made the macro-crack be controlled and the ceramic densification be promoted evidently. XRD results showed the eutectic ceramics were composed of α-Al2O3, t-ZrO2 and a few m-ZrO2 phases, and the volume fraction of the transformable t-ZrO2 increased with self-pressure force increasing. SEM images showed that with increasing self-pressure force, the rod-shaped eutectic colonies were refined and the volume fraction of the colonies increased. Meanwhile, the irregular ZrO2 crystals around eutectic colonies transformed to be fine t-ZrO2 spherical crystals gradually, and thickness of eutectic colonies decreased. With the changes in microstructures of the ceramics, the mechanical properties of the ceramics were improved greatly.

Microstructure Transformation and Mechanical Properties of the Large-Bulk Solidified Al2O3-ZrO2 (Y2O3) Micro-Nanocrystalline Composites Prepared by Combustion Synthesis under High Gravity

2010 ◽  
Vol 177 ◽  
pp. 132-135
Author(s):  
Zhong Min Zhao ◽  
Long Zhang ◽  
Yi Gang Song ◽  
San Qun Li ◽  
Wei Guo Wang
Keyword(s):  
Combustion Synthesis ◽  
Solidification Process ◽  
Ceramic Composites ◽  
Nucleation Theory ◽  
High Gravity ◽  
Tetragonal Zro2 ◽  
Microstructure Transformation ◽  
Large Bulk ◽  
Coupled Growth ◽  
Spherical Crystals

Based on preparing the large-bulk solidified Al2O3-ZrO2 (Y2O3) ceramic composites by combustion synthesis under high gravity, the solidification behavior and microstructure transformation of the ceramics as well as their effects on the ceramic properties were investigated. XRD, SEM and EDS analyses showed the ceramic microstructures were composed of the irregular eutectics at the surface and the tetragonal ZrO2 micrometer spherical crystals in the center of the ceramics respectively. By combining with irreversible nucleation theory, it is considered that the formation of irregular eutectics with micro-nanocrystalline microstructures is a result of the leading nucleation of Al2O3 high-fusion-entropy phases followed by the coupled growth of Al2O3-ZrO2 phases, whereas the presence of the tetragonal ZrO2 spherical microstructures in the center of the ceramics results from the leading nucleation of ZrO2 cubic phases followed by the independent growth of Al2O3-ZrO2 phases. As a result, it is just the unique microstructure transformation during the solidification process that the highest hardness at the surface and the highest fracture toughness in the center of the ceramics are achieved respectively.

High-Hardness Solidified TiB2-TiC Composites Prepared by Combustion Synthesis under High Gravity

2011 ◽  
Vol 233-235 ◽  
pp. 1734-1739
Author(s):  
Tao Ma ◽  
Zhong Min Zhao ◽  
Long Zhang ◽  
Xue Gang Huang ◽  
Liang Xiang Liu
Keyword(s):  
Flexural Strength ◽  
Combustion Synthesis ◽  
High Hardness ◽  
Full Density ◽  
High Gravity ◽  
Composite Ceramics ◽  
Rapid Separation ◽  
Fine Grained ◽  
Large Bulk ◽  
High Gravity Field

Large-bulk TiB2-TiC composite ceramics were prepared by combustion synthesis under high gravity. XRD, SEM and EDS results showed TiB2-TiC composites were mainly composed of the fine-grained microstructures of TiC matrix in which a large number of the fine TiB2 platelet grains were dispersed uniformly, whereas there discontinuously dispersed the ε-carbides with the enrichment of Ti atoms, and a few of isolated, irregular α-Al2O3 grains and Al2O3-ZrO2 colonies were also observed at the boundaries of the eutectic microstructures. The results of properties indicate that with increasing mass fraction of B4C+Ti+C in combustion systems, the relative density and fracture toughness of TiB2-TiC composites are all among 97%~99% and 6.5~7.1 MPa·m1/2, respectively, and the Vickers hardness and flexural strength are increased gradually to the maximum values of 28.6GPa and 615MPa, respectively. The achievement of full-density TiB2-TiC composites benefited from the design of full-liquid SHS products and the introduction of high-gravity field, and high hardness of the composite ceramics resulted from the absence of intermediate borides and the achievement of stoichiometric TiC phases due to rapid solidification, whereas high flexural strength of the composite ceramics benefited from the homogenization and refinement of the microstructures due to the rapid separation of the liquid oxides and the rapid coupled growth of TiB2-TiC.

Preparation of Fe3Al Alloy by Combustion Synthesis Melt-Casting under Ultra-High Gravity

2011 ◽  
Vol 27 (5) ◽  
pp. 486-489 ◽  
Author(s):  
Peilin Mai ◽  
Guanghua Liu ◽  
Yixiang Chen ◽  
Jiangtao Li ◽  
Shuli He
Keyword(s):  
Combustion Synthesis ◽  
High Gravity ◽  
Fe3al Alloy

Al2O3/ZrO2 (Y2O3) PREPARED BY COMBUSTION SYNTHESIS UNDER HIGH GRAVITY

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1148-1153 ◽  
Author(s):  
LONG ZHANG ◽  
ZHONGMIN ZHAO ◽  
YIGANG SONG ◽  
WEIGUO WANG ◽  
HONGBO LIU
Keyword(s):  
Fracture Toughness ◽  
Flexural Strength ◽  
Combustion Synthesis ◽  
High Fracture Toughness ◽  
High Gravity ◽  
Transformation Toughening ◽  
Composite Ceramics ◽  
Directionally Solidified ◽  
High Fracture ◽  
Toughening Mechanisms

By introducing ZrO 2 (4 Y ) powder into the thermit, Al 2 O 3/ ZrO 2 (4 Y ) composite ceramics of different composition and microstructures were prepared through combustion synthesis under high gravity, and the correlations of composition, microstructures and mechanical properties of composite ceramics were investigated. The results of XRD, SEM and EDS showed that Al 2 O 3/33% ZrO 2 (4 Y ) were composed of random-orientated rod-shaped colonies consisting of a triangular dispersion of orderly submicron-nanometer t - ZrO 2 fibers, surrounded by inter-colony regions consisting of spherically-shaped micronmeter t - ZrO 2 grains; meanwhile, Al 2 O 3/45% ZrO 2 (4 Y ) were comprised of spherically-shaped micron-meter t - ZrO 2 grains. Similar to the international directionally solidified Al 2 O 3/ ZrO 2 ( Y 2 O 3), the EDS results also indicated that there are no impurities, amorphous phases and grain boundaries but clean phase interfaces in two ceramic composites. Compared to the international directionally solidified Al 2 O 3/ ZrO 2 ( Y 2 O 3), the increase in hardness and flexural strength of Al 2 O 3/33% ZrO 2 (4 Y ) in the experiment was due to small-size defect and high fracture toughness induced by compressive residual stress effect and transformation toughening mechanisms; meanwhile, high flexural strength of Al 2 O 3/45% ZrO 2 (4 Y ) was considered to be a result of the fine spherically-shaped t - ZrO 2 grains separated from the melt under high gravity, and high fracture toughness induced by transformation toughening and micro-crack toughening mechanisms.

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