Manufacture And Research On The Mechanical Properties Of Alumina-based Diphase Ceramics

Alumina ceramics materials were widely used, but its low fracture toughness restricted its wider application. The mechanical properties of alumina ceramics can be improved through the whisker toughening and particle toughening by the suitable selection of the second phase. The grain growth of Al2O3 can be hindered by adding TiC and TiN particles with high melt point and high hardness, which made the diphase ceramics have high hardness and hard strenghness. At the same time, the dispersed second phase particles can block the extension of the cracks, which do some good to the increase of the fracture toughness of the diphase ceramics. As a result, in this paper, these two kinds of powder particles with different granularities were selected to add to the alumina for the sake of obtaining the excellent mechanical properties.There were many researches on Al2O3-based diphase ceramics, but few of them focused on the methods of the fracture toughness measurement of alumina-based diphase ceramics. This paper specially researched the selection of the most suitable indentation method calculation equation and the effect of the powders granularities on the selection of the equation which is most suitable for this system materials when the indentation method was used to evaluate the fracture toughness of these materials; studied the effect of the indentation loads on the fracture toughness of these materials; compared and analyzed the KIC values of these materials obtained by IM method and SENB method; studied the effect of the applied indentation loads on the reliability of the IM method.Hot press sintering is often used to manufacture the alumina-based diphase ceramics. The technique of sintering commonly is 1600~ 1700℃ ×30MPa× 1h, and the protection atmosphere is N2. The selection of the sintering parameters has effect on the mechanical properties of the sintering materials to some extent. In this paper, the influence of the sintering temperature on the microstructure and the mechanical properties of the materials were investigated. It was found that with the increase of the sintering temperature, the density of the materials and the KIC values was increasedand decreased, respectively. But the Vickers hardness and the bend strength of the materials obtained the max. at the temperature of 1650℃. Then, it was concluded that the optimal sintering temperature is 1650 ℃ when these materials with the components were prepared. In addition, we also discussed the effect of the granularities of the powders and the added phases on the mechanical properties of the alumina-based diphase ceramics. It was found that the material A2 with micrometer matrix strengthened by sub-micrometer second phase had the best comprehensive mechanical properties. When TiC and TiN powders were added into the alumina matrix at the same time, the density and the mechanical properties of the material were both improved .Contrasted to the monolithic nanometer alumina, the flexure strength of this material was increased from 419MPa to618MPa and the KIC value was increased from3.42MPa · m1/2 to 4.37 MPa · m1/2.Therefore, we can say that this material was strengthened and toughened at the same time.