3) Strengthening of perform
The strength of the preform after debinding is too weak to avoid deformation or damage during infiltration. It can be strengthened through the following two methods:
(1) High temperature calcination
High temperature calcination enhances the strength of SiC preform by virtue of the generated SiO2 layer on SiC. Too high temperature induces the formation of obturated pores, which are difficult to be infiltrated. A better calcination condition is found to be at 1 100 °C for 8 h in vacuum [8]. The disadvantage is that chemical reaction between Al alloys and SiO2 film will reduce the thermal properties.