Measurement of the effect of microstructural variations on the energy of (Co, Ni)-Cr23 C6 eutectic
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The measurement of sector areas of load-deflection curves in the Tattersall-Tappin test permits evaluation of the fracture energy dissipated by the microstructure during crack propagation. This method has been applied to the oriented pseudo-binary (Co, Ni)-Cr23C6 eutectic alloys which exhibit an irregular, continuous network of brittle carbides within a ductile (Co, Ni, Cr) phase. In spite of the complexity of the microstructure analysed, the method proposed for measuring the fracture energy seems to be capable of revealing the fundamental influence of the size, volume and properties of the phases on the fracture energy of the alloys. An increase in the fracture energy for crack propagation has been observed with: (a) an increase in the size (spacing) of the phases for a constant volume fraction; (b) an increase in the volume fraction of the ductile phase; (c) a progressive increase of the Ni content of the alloy (for values above 5 wt % Ni); the highest values being observed for the pure ternary system: Co-Cr23C6 and Ni-Cr23C6.
KeywordsCarbide Fracture Energy Eutectic Alloy Fracture Path Stable Crack Growth
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