Effect of Test Temperature and Strain Rate on the Yield Stress of Monocrystalline 6H-SiC

The critical resolved shear stress for activating the (0001) 〈21-1-0〉 slip system of monocrystalline 6H-SiC has been determined as a function of test temperature and strain rate via constant-displacement compression tests. Tests were conducted at temperatures between 550 and 1300 °C at strain rates of 1.3×10—4, 6.3×10ü—5 and 3.1×10ü—5 s—1. The current study shows that 6H-SiC crystals can be plastically deformed via relatively modest resolved shear stresses on the basal plane at temperatures as low as ≈︂550 °C. For temperatures below ≈︂1300 °C for the fast and intermediate strain rates, and for temperatures below ≈︂1100 °C for the slow strain rate, the stress exponent n, and the activation enthalpy H(2.1 ± 0.7) eV, respectively. At higher temperatures at the slowest strain rate, the activation enthalpy was determined to be (4.5 ± 1.2) eV. Subsequent to the deformation tests, transmission electron microscopy (TEM) was used to rationalize some of the results.