| Ceramic reinforced Al matrix composite is a kind of strong vitality material,which meets the demand of modern scientific development and engineering technology. The combination between the high strength, hardness, elastic modulus and wear resistance of ceramic and the low density, high ductility and toughness of Al results in its comprehensive characteristics of light weight, high strength and wear resistance. Therefore, ceramic reinforced Al matrix composite is treated as a kind of the most promising candidate materials in aviation, aerospace, weapons,vehicles, ships and other fields of engineering components. However, the addition of ceramic reinforcement such as Ti C, Ti B2, Al2O3, Si C, B4 C and so on increases the specific strength and specific modulus and decreases ductility and tenacity of Al matrix composite, which reduces its impact resistance and enlarge the brittle rupture possibility. These shortcomings are the main failure modes of Al matrix composite structure component, whch greatly limit its application in the working conditions of high impact, stress and pressure. The fabrication of ceramic reinforced Al matrix composite with the characteristics of high strength, hardness, ductility, light weight,high strength, crack arrest and impact resistance is important to improve the comprehensive performance of engineering components.Many kinds of biologies such as the shellfishes, manis pentadactyla, desert lizard, scales of soil animals, wood, bamboo, bone and tooth of human and animals and so on own the properties of light weight, high strength and impact resistance,providing important references for improving the properties of engineering materials.White clam shell is the bionic model of this thesis. Based on the characteristics of light weight, high strength and impact resistance of white clam shell, a kind of bionic layered impact resistance material of Al-Ti-B4 C system is fabricated by corporation method of combustion synthesis and hot pressing sintering. This bionic layered material possesses the capabilities of light weight, high strength and impact resistance and provides the new idea, approach and method for the application of ceramic/Al composite in engineering. The research conclusions are described as follows.(1) In macro aspect, white clam shell can be divided into horny layer, prismatic layer and nacreous layer, which exhibits the model of “hard-soft-hardest” from out layer to inner layer. In micro aspect, crossed-lamellar structure is the microstructure characterization of prismatic layer and nacreous layer. The phase component of three layers is Ca CO3 with crystallization morphology of aragonite. Flexible organic matter connects thecontiguous lamels, which exhibts the characteristic of combination between hard and soft.(2) White clam shell owns perfect mechanical properities. With the thickness of1.0mm-1.5mm, the average values of flexure and compression strength are110.2Mpa and 80.1MPa, respectively. Under the condation of impact impression,materials on the surface are expanded to surrounding, reducing the phenomeon of stress concentration in macro aspect. Moreover, in the micro aspect,discontinuous fracture of lamels leads to crack deflection phenomeon, which forbids the extension of cracks.(3) The simplified structure model of bionic layered impact resistance material was estiblshed. Based on this model, the 40 wt.% Al-Ti-B4 C system is the outer layer.50 wt.% Al-Ti-B4 C system is the middle layer. 30 wt.% Al-Ti-B4 C system is the inner layer. Al-Ti-B4 C layers are connected with the soft Al layer, which forms the “hard-soft-hardest” model.(4) Bionic layered impact resistance material was fabricated successfully by corporation method of combustion synthesis and hot pressing sintering. In macro aspect, the hard layer of Ti C-Ti B2/Al and the soft layer of Al result in bionic layered impact resistance material with multilayer structure possessing characteristic of combination between hard and soft. In micro aspect, Ti C and Ti B2 ceramics and soft Al constitute hard layer of Ti C-Ti B2/Al. Ti C and Ti B2 exhibites staggered distribution, which connects with soft Al and shows the characteristic of combination between hard and soft. Bionic layered impact resistance material achieves the bionic efficient reproduction of bionic model founctions.(5) Bionic layered impact resistance material owns high flexural strength, fracture toughness, compressive strength and impact toughness. Under the loads of bending, compression and impact, hard layers bear applied loads, and soft layers absorb and release stress with plastic deformation. Hard and inflexibility phase of nionic layered impact resistance material plays the key role in strengthing impact resistance. Soft and tenacity phase plays the key role in absorbing stress.The combination between inflexibility and tenacity is the typical impact resistance characteristic and mechanism of bionic layered impact resistance material. |
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