Alumina Ceramics Toughened Its Microscopic Mechanism Study

Alumina is a widely used ceramic due to its refractoriness, high hardness, good wear resistance and high chemical stability, however, its brittleness limits its applications. To enhance the fracture toughness (KIC) of alumina ceramic and to reduce its brittleness are the main topic of this paper. This paper investigated the effect of nano SiC enhanced alumina ceramic toughness and its microstructure and mechanical properties. The result indicates that the nano SiC is in the crystal boundary mostly and the toughness of alumina ceramic is enhanced because of the crack deflexion mechanism. This paper also studied the properties and microstructure of metal-SiC-alumina composite ceramic. The investigation indicate that owing to metal grain bridge unite and nano SiC nail prick function the toughness of alumina composite ceramic can be enhanced. The fracture toughness (KIC) can reach 3. 76 MPa m1/2 when 10% Fe is added into alumina composite ceramic and the fracture toughness (KIc) can reach 3.97 MPa m1/2 when 10% Ni is added into alumina composite ceramic. Since MgO whiskers have high melting point, high strength and good plasticity and MgO whiskers can be grown from MgB2 by oxidation. This paper also investigated the MgB2 enhanced alumina ceramic. When MgB2 accede to alumina ceramic its microstructure and mechanical properties will be affected. We discovered that when temperature is 800C, bamboo-like MgO whiskers will grow in Al2O3 ceramics. When temperature is 1450C, alumina ceramic grains with columnar shape are grown. The effects of the addition of other magnesium compound in alumina were also studied in this paper. When MgF2 accede to alumina ceramic and the sintering temperature is 1450C, the grains with tetrahedron shape will be formed. When MgCl2 was added into alumina ceramic its effect is similar as MgO additive.