Transition from brittleness to ductility in SiC

• Published in: Journal of physics. Condensed matter Vol. 14; no. 48; pp. 12929 - 12945
• Main Authors: Pirouz, P, Zhang, M, Demenet, J-L, Hobgood, H M
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Bristol IOP Publishing 16.12.2002; Institute of Physics
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Fatigue, brittleness, fracture, and cracks; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Physics; Transition temperature; Inorganic compounds; Ruptures; Silicon carbides; Experimental study; Dislocations; Cracks; Ductile-brittle transitions; Crack tip; Wide band gap semiconductors; Activation energy; Bending test; Strain rate
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/14/48/335

Following an initial elastic strain, a crystal responds to an increasing external stress by either breaking up into pieces, or else plastically changing its shape before failure. In this paper, the different behaviours of a crystal-brittle cleavage versus ductile deformation-are briefly discussed, and the transition from one regime to the other is developed in a simple intuitive manner. The two responses are related and models developed for predicting the transition temperature from a brittle to a ductile behaviour. In addition, experimental measurements of the transition temperature in a wide bandgap semiconductor, 4H-SiC, are outlined and data presented. The results appear to be consistent with a transition temperature T sub c recently observed in the yield stress of the same material as measured by compression experiments. However, strain rate measurements in four-point bend tests are not strictly equivalent to those in compression experiments because of the different sample geometries used in the two cases. It is thus difficult to make a direct comparison of the measured brittleness to ductility temperatures with the yield stress transitions.