A novel in situ reaction system Al Zr O was developed. In situ Al 3Zr and Al 2O 3 particulate reinforced A356 alloy matrix composites have been fabricated by direct melt reaction method. The results show that the maxi...A novel in situ reaction system Al Zr O was developed. In situ Al 3Zr and Al 2O 3 particulate reinforced A356 alloy matrix composites have been fabricated by direct melt reaction method. The results show that the maximum sizes of Al 3Zr and Al 2O 3 particulates synthesized in the system ZrOCl 2 A356 are 1 μm and 3 μm respectively, and they are well distributed in the matrix. The investigation shows that the Al 3Zr crystal is in the shape of polyhedron and rectangle. There is a faceted growth phenomenon on Al 3Zr crystal surface. It is firstly found that the Al 3Zr crystal grows in the mechanism of twinning. The twinning plane is (1 1 4), and the twinning direction is [2 2 1] . The crystal morphology of in situ α Al 2O 3 particulate is rectangle or sphere. Furthermore, (Al 3Zr+Al 2O 3) p/A356 composites have not only higher tensile strength at room temperature (376.2 MPa) but also higher yield strength (319.4 MPa) and higher tensile strength at elevated temperature (200 ℃) than those of the A356 alloy. The dry sliding wear test shows that the wear resistance of the (Al 3Zr+Al 2O 3) p/A356 composites is greatly enhanced with increasing particulate volume fraction.展开更多
A novel in-situ reaction system Al-Zr-O was developed. In-situ Al3Zr and Al2O3 particulates reinforced aluminum matrix composites were fabricated by the direct melt reaction technique in the Al-Zr-O system. Microstruc...A novel in-situ reaction system Al-Zr-O was developed. In-situ Al3Zr and Al2O3 particulates reinforced aluminum matrix composites were fabricated by the direct melt reaction technique in the Al-Zr-O system. Microstructures of the composites and crystal morphology of in-situ formed Al3Zr and Al2O3 particulates were analyzed by scanning electron microscope（SEM） and transmission electron microscope（TEM）. Results indicate that in-situ formed Al3Zr and Al2O3 particles are finer and well distributed in aluminum matrix. Al3Zr particulates with a tetragonal structure are mainly in the shape of polyhedron. A few of them are in the form of rectangle. The length/width ratio of the rectangular Al3Zr is less than 2.0 and the maximum size is 2 μm. In addition, a certain number of Al2O3 submicro particles with a hexagonal structure are also generated in this system. Furthermore, it is found that Al3Zr crystal grows by the mechanism of twinning. The twin plane is （11-4-）. The twinning direction is [221].The tensile tests show that the composites synthesized in the Al-Zr-O system exhibits high strength and ductility. There are a lot of ripples with fine particles on the fracture. The principal strengthening mechanisms for （Al3Zr+Al2O3）p/Al composites may include Orowan strengthening, grain-refining strengthening, solid-solution strengthening and dislocation strengthening.展开更多
Zirconia-mullite nano-composite ceramics were fabricated by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk, which were first treated at 900-1000 ℃ for nucleation, then treated at higher temperature f...Zirconia-mullite nano-composite ceramics were fabricated by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk, which were first treated at 900-1000 ℃ for nucleation, then treated at higher temperature for crystallization to obtain ultra-fine zirconia-mullite composite ceramics. The effects of treating temperature and ZrO2 addition on mechanical properties and microstructure were analyzed. A unique structure in which there are a lot of near equiaxed t-ZrO2 grains and fine yield-cracks has been developed in the samples with 15% zirconia addition treated at 1 150 ℃ . This specific microstructure is much more effective in toughening ceramics matrix and results in the best mechanical properties. The flexural strength and fracture toughness are 520 MPa and 5.13 MPa·m1/2, respectively. Either higher zirconia addition or higher crystallization temperature will produce large size rod-like ZrO2 and mullite grains, which are of negative effect on mechanical properties of this new composite ceramics.展开更多
文摘A novel in situ reaction system Al Zr O was developed. In situ Al 3Zr and Al 2O 3 particulate reinforced A356 alloy matrix composites have been fabricated by direct melt reaction method. The results show that the maximum sizes of Al 3Zr and Al 2O 3 particulates synthesized in the system ZrOCl 2 A356 are 1 μm and 3 μm respectively, and they are well distributed in the matrix. The investigation shows that the Al 3Zr crystal is in the shape of polyhedron and rectangle. There is a faceted growth phenomenon on Al 3Zr crystal surface. It is firstly found that the Al 3Zr crystal grows in the mechanism of twinning. The twinning plane is (1 1 4), and the twinning direction is [2 2 1] . The crystal morphology of in situ α Al 2O 3 particulate is rectangle or sphere. Furthermore, (Al 3Zr+Al 2O 3) p/A356 composites have not only higher tensile strength at room temperature (376.2 MPa) but also higher yield strength (319.4 MPa) and higher tensile strength at elevated temperature (200 ℃) than those of the A356 alloy. The dry sliding wear test shows that the wear resistance of the (Al 3Zr+Al 2O 3) p/A356 composites is greatly enhanced with increasing particulate volume fraction.
基金Project(50471050) supported by the National Natural Science Foundation of China Project(00170) supported by the KeyFoundation of the Ministry of Education of China Project(BE2002039) supported by Jiangsu Provincial Key Project of Science and Tech
文摘A novel in-situ reaction system Al-Zr-O was developed. In-situ Al3Zr and Al2O3 particulates reinforced aluminum matrix composites were fabricated by the direct melt reaction technique in the Al-Zr-O system. Microstructures of the composites and crystal morphology of in-situ formed Al3Zr and Al2O3 particulates were analyzed by scanning electron microscope（SEM） and transmission electron microscope（TEM）. Results indicate that in-situ formed Al3Zr and Al2O3 particles are finer and well distributed in aluminum matrix. Al3Zr particulates with a tetragonal structure are mainly in the shape of polyhedron. A few of them are in the form of rectangle. The length/width ratio of the rectangular Al3Zr is less than 2.0 and the maximum size is 2 μm. In addition, a certain number of Al2O3 submicro particles with a hexagonal structure are also generated in this system. Furthermore, it is found that Al3Zr crystal grows by the mechanism of twinning. The twin plane is （11-4-）. The twinning direction is [221].The tensile tests show that the composites synthesized in the Al-Zr-O system exhibits high strength and ductility. There are a lot of ripples with fine particles on the fracture. The principal strengthening mechanisms for （Al3Zr+Al2O3）p/Al composites may include Orowan strengthening, grain-refining strengthening, solid-solution strengthening and dislocation strengthening.
基金Project supported by Foundation for Innovative Research Groups of ChinaProject(50634060) supported by the National Natural Science Founation of China
文摘Zirconia-mullite nano-composite ceramics were fabricated by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk, which were first treated at 900-1000 ℃ for nucleation, then treated at higher temperature for crystallization to obtain ultra-fine zirconia-mullite composite ceramics. The effects of treating temperature and ZrO2 addition on mechanical properties and microstructure were analyzed. A unique structure in which there are a lot of near equiaxed t-ZrO2 grains and fine yield-cracks has been developed in the samples with 15% zirconia addition treated at 1 150 ℃ . This specific microstructure is much more effective in toughening ceramics matrix and results in the best mechanical properties. The flexural strength and fracture toughness are 520 MPa and 5.13 MPa·m1/2, respectively. Either higher zirconia addition or higher crystallization temperature will produce large size rod-like ZrO2 and mullite grains, which are of negative effect on mechanical properties of this new composite ceramics.
