SiC whisker reinforced aluminum composites are fabricated by vacuum hot pressing. The whisker is a kind of fine needle-like fibrous material that exists in the form of a single crystal without defects. Its internal structure is absolutely complete and defect-free. The whisker-reinforced composites have many excellent properties. SiC whiskers are widely used in metallic matrix composites as whisker reinforcements with excellent properties. Among them, SiC whisker reinforced aluminum composites have been widely used in aerospace, automotive and other industries due to their high specific strength and hardness and good dimensional stability.
The key to fabricating SiC whisker reinforced aluminum composites lies in the uniform distribution of whiskers in the matrix, and the strong bonding between whiskers and aluminum. Now, the most important techniques for preparing SiC whisker reinforced aluminum composites are die-casting and powder metallurgy. Recently, powder metallurgy has become one of the main processes for fabricating high-performance aluminum-based composites.
In the hot-pressing sintering process, the thermal conductivity values of the aluminum powder and SiC whiskers that constitute the raw mixture change with increasing sintering temperature, while the relative density of the raw mixture changes with increasing sintering pressure. When the sintering temperature is too high, the grain growth occurs, which decreases the relative density of sintered compacts. As a result, the mechanical properties decrease. It is also difficult to separate the sintered compacts from dies after sintering because of the melting of sintered compact into dies. Therefore, some process problems arise, such as the difficulty of repeated use of dies.
Kim Kuk Il, a researcher at the Faculty of Materials Science and Technology, conducted a simulation analysis of the temperature distribution in the die and the raw mixture during sintering, and experimentally confirmed it. On this basis, he has presented a new question for determining the sintering conditions such as sintering temperature, heating rate and holding time, and investigated it.
As a result, he has confirmed the optimum sintering temperature (600℃), heating rate (15℃/min) and holding time (15min).
© 2021 Kim Chaek University of Technology