Effects of Al powders addition on microstructure and properties of automobile Al₂O₃ powders prepared by hot-pressing molding

The automobile Al₂O₃ powder samples were prepared by hot-pressing molding, using Al powders as the modifying agents, the effects of Al powder content by mass on the microstructure and mechanical properties of Al₂O₃ powder samples were studied. The results show that, the maximum shrinkage rate appears in the length direction of Al₂O₃ powder samples and the minimum one appears in the height direction. With the increase of Al powders content by mass, the shrinkage rate of Al₂O₃ powder samples decreases first and then increases steadily, and finally decreases. With the increase of Al powders content by mass, the bending strength and volume density of Al₂O₃ powder samples decrease, while the porosity increase significantly. In addition, the Al₂O₃ powder samples show a larger deflection, the structure with larger pore diameter can be obtained by hot-pressing molding, and the number of larger pore in Al₂O₃ powder samples also increases significantly. With the increase of Al powders content by mass, the diffraction peak of Al₂O₃ increases continuously, but the glass phase changes finitely. When the mass fraction of Al powders is 8%, the obvious grain structure is formed in the fracture area of Al₂O₃ powder samples and the intergranular fracture is mainly occurred.