Joining of SiC by tape-cast SiC-Al_2O_3-Y_2O_3 interlayer

摘要

SiC substrates were successfully bonded by tape-cast SiC-Al_2O_3-Y_2O_3 interlayers in the temperature range of 1800-1900 ℃ for 60 min at 15 MPa pressure in flowing Ar. Based on microstructure observations, we find that the α-SiC interlayers result in equiaxed microstructure at all joining temperatures while the tape-cast β-SiC leads to a microstructure varying from a mixed characteristic to an elongated one with joining temperature. The detailed image analysis suggests the close interlayer thickness, the quicker grain growth rate of β-SiC relative to α-SiC one and the good agreement between aspect ratio and morphology in all joints. Moreover, the SiC grains of interlayer near to interface develop preferentially from the external SiC grains of substrate, which is possibly related to the morphology difference between substrate and interlayer and the grain growth behaviors. Finally, the SiC joined with tapes exhibits an average bending strength over 359 MPa and usually fracture within SiC bases.