Microstructure and Hardness Distribution of Seven-Layered Al-Al2O3 Graded Composite Material Prepared Through Pressureless Sintering
摘要
In the present study, different percentages of Aluminium (Al) and Aluminium Oxide (Al2O3) were integrated layer by layer for preparation of seven-layered graded composite material. Due to large difference in properties, crack or defect is the main problem for metal-ceramic combination. The prepared graded structure was investigated layer by layer for any defect or crack that might appear in the layer or at the interface. By using a steel die set combination, different layers of different percentages of metal-ceramic were integrated in preparation of the graded composite. After that a pressureless two-step sintering method was used. During the sintering process, a maximum temperature of 630 °C was applied for 3 h sintering duration. Each layer of graded specimen and interfaces of different layers were characterized using Field Emission Scanning Electron Microscopy (FESEM). Vickers microhardness testing was carried out for different layers of composite. The obtained results showed that there is a good distribution of ceramic (Al2O3) particles into metallic (Al) matrix when ceramic content up to the 20% (fifth layer). On the other hand, it was also observed that when ceramic content more than 20%, agglomeration occurred for the sixth and seventh layer. Microstructural observations showed that layers boundary and all interfaces are almost parallel. Moreover, it was obvious that no crack was found in the layer or at the interface which confirmed the good preparation process of graded structure.