Al2O3-ZrO2 with a high level of hardness and toughness is known as ceramic steel. Due to its unique properties it can be used as a reinforcement in fabrication of metal matrix composites. In this study, nanoparticles ...Al2O3-ZrO2 with a high level of hardness and toughness is known as ceramic steel. Due to its unique properties it can be used as a reinforcement in fabrication of metal matrix composites. In this study, nanoparticles of Al2O3-10% ZrO2 with an average size of 80 nm were used to fabricate Al matrix composites containing 0.5, 1, 1.5 and 2 wt.% of the reinforcement. The fabrication route was stir casting at 850?C. There is no report about usage of this reinforcement in fabrication of composites in the literature. The microstructures of the as-cast composites were studied by scanning electron microscope (SEM). Density measurement, hardness and tensile properties were carried out to identify the mechanical properties of the composites. The results revealed that with increasing the reinforcement content, density decreased while yield, ultimate tensile strength and compressive strength increased. Also, hardness increased by increasing the reinforcement content up to 1 wt.% Al2O3-10% ZrO2 but it decreased in the samples containing higher amounts of reinforcement.展开更多
To fabricate W-ZrC composite through reaction sintering at first WC and ZrO2 powders with molar ratio of 3-1 are ball milled, then the green body made from this mixture is sintered. Since reactivity is the main proble...To fabricate W-ZrC composite through reaction sintering at first WC and ZrO2 powders with molar ratio of 3-1 are ball milled, then the green body made from this mixture is sintered. Since reactivity is the main problem in sintering of mironized powders the starting ZrO2 powder is selected in nano size to see whether the reaction improves. The XRD pattern indicates that W-ZrC composite has been formed, although some unreacted compounds still exist and some unwanted components have been created. In the case of using nano powders the amount of unreacted WC and ZrO2 phases and unwanted W2C phase reduces and the reaction progresses better. Additionally by using nano powders the reaction progressed and the mechanical proprieties including density, hardness, Elastic modulus and Flexural strength improved.展开更多
In this article,a new method has been presented for the estimation of fracture toughness in brittle materials,which enjoys improved accuracy and reduced costs associated with fracture toughness testing procedure compa...In this article,a new method has been presented for the estimation of fracture toughness in brittle materials,which enjoys improved accuracy and reduced costs associated with fracture toughness testing procedure compared to similar previous methods,because a vast range of specimens with irregular cracks can be accommodated for testing.Micron-sized alumina powders containing 0.05 wt%magnesium oxide(MgO)nanoparticles were mixed and also together with 2.5 vol%,5 vol%,7.5 vol%,10 vol%,and 15 vol%of silicon carbide(SiC)nanopowders separately.By making and testing various types of ceramics with different mechanical properties,and considering the irregular cracks around the indented area caused by Vickers diamond indenter,a semi-empirical fracture toughness equation has been obtained.展开更多
文摘Al2O3-ZrO2 with a high level of hardness and toughness is known as ceramic steel. Due to its unique properties it can be used as a reinforcement in fabrication of metal matrix composites. In this study, nanoparticles of Al2O3-10% ZrO2 with an average size of 80 nm were used to fabricate Al matrix composites containing 0.5, 1, 1.5 and 2 wt.% of the reinforcement. The fabrication route was stir casting at 850?C. There is no report about usage of this reinforcement in fabrication of composites in the literature. The microstructures of the as-cast composites were studied by scanning electron microscope (SEM). Density measurement, hardness and tensile properties were carried out to identify the mechanical properties of the composites. The results revealed that with increasing the reinforcement content, density decreased while yield, ultimate tensile strength and compressive strength increased. Also, hardness increased by increasing the reinforcement content up to 1 wt.% Al2O3-10% ZrO2 but it decreased in the samples containing higher amounts of reinforcement.
文摘To fabricate W-ZrC composite through reaction sintering at first WC and ZrO2 powders with molar ratio of 3-1 are ball milled, then the green body made from this mixture is sintered. Since reactivity is the main problem in sintering of mironized powders the starting ZrO2 powder is selected in nano size to see whether the reaction improves. The XRD pattern indicates that W-ZrC composite has been formed, although some unreacted compounds still exist and some unwanted components have been created. In the case of using nano powders the amount of unreacted WC and ZrO2 phases and unwanted W2C phase reduces and the reaction progresses better. Additionally by using nano powders the reaction progressed and the mechanical proprieties including density, hardness, Elastic modulus and Flexural strength improved.
文摘In this article,a new method has been presented for the estimation of fracture toughness in brittle materials,which enjoys improved accuracy and reduced costs associated with fracture toughness testing procedure compared to similar previous methods,because a vast range of specimens with irregular cracks can be accommodated for testing.Micron-sized alumina powders containing 0.05 wt%magnesium oxide(MgO)nanoparticles were mixed and also together with 2.5 vol%,5 vol%,7.5 vol%,10 vol%,and 15 vol%of silicon carbide(SiC)nanopowders separately.By making and testing various types of ceramics with different mechanical properties,and considering the irregular cracks around the indented area caused by Vickers diamond indenter,a semi-empirical fracture toughness equation has been obtained.
