CREEP OF 6H ALPHA-SILICON CARBIDE SINGLE-CRYSTALS

The compressive creep behavior of single-crystal 6H alpha-SiC was measured for orientations parallel to and at 45-degrees to [0001]. Deformation of the 45-degrees orientation was dominated by basal slip. Steady-state creep rates above 10(-7)/s were measured at temperatures as low as 800-degrees-C. An activation energy of 277 kj/mol and a stress -exponent of 3.32 were determined. Creep testing with applied stresses parallel to [0001] was performed at 1650-degrees-C to 1850-degrees-C, yielding a stress exponent and activation energy of 4.93 and 180 kj/mol, respectively. The occurrence of basal slip in the [0001] specimens suggested that significant off-axis stresses were present during testing.