On-line version ISSN 1678-4553
FREITAS, M. et al. Preparation and characterization of SiC/kaolin/Al composite materials by squeeze- casting. Cerâmica [online]. 2009, vol.55, n.335, pp. 271-280. ISSN 1678-4553. http://dx.doi.org/10.1590/S0366-69132009000300006.
In search of materials with different properties, has been increasing the research on composite materials in recent years. One of the important methods of manufacturing these composites is the process of metal casting infiltration under pressure called squeeze-casting. This process offers some advantages, such as ease of producing the composite, low cost and ability to form network structures. In this work were produced and characterized Al-SiC composites, with concentrations in kaolin ranging between 10 and 50% in place to SiC majority phase. The ceramic pre-forms were produced to controlling the fraction of the size SiC/kaolin for better infiltration. These pre-forms after sintering at 1100 ºC/1 h resulted highly porous, and the porosity increased with the increase of kaolin in place to SiC particles. XRD analysis showed the existence of quartz particles beyond the SiC phase. During the infiltration and heat treatment process, the liquid aluminum reacted preferably with quartz and other aluminosilicates particles of the pre-form reducing them, precipitating alumina and silicon in the microstructure, which also presented aluminum in excess that not reacted in the process. The silica and silicates of pre-form, reacted preferably with the aluminum, preventing the formation of Al4C3 phase, which is highly hygroscopic and causes the composite degradation. Depending on the composition, the SiC - kaolin - Al composite developed in this work, can be used in applications involving high bending mechanical resistance (240 to 300 MPa), low density and hardness surface between 180 and 380 kgf/mm2.
Keywords : CMC composites; microstructure; silicon carbide; infiltration; kaolin; squeeze-casting.