The effect of aging on the serrated yielding and intermediate temperature embrittlement of nickel-base C-276 alloy

The influence of aging on serrated yielding and intermediate temperature embrittlement (ITE) of nickel-based C-276 alloy has been investigated by microstructural characterization and tensile tests at temperatures ranging from 300 to 950 °C with strain rate of 3 × 10-4 s-1. The precipitated phases in the C-276 alloy aged at 870 °C for various times were identified as μ phase and M6C. Tensile ductilities obtained at 700 °C were found to increase with extending aging time until 12 h, and thereafter, it remained almost unaffected by the aging time. Serrated flow was noticed for all temperatures for the solutionized alloy, and the alloy presented the typical ITE. Aging the solutionized alloy at 870 °C/36 h resulted in a disappearance of serrated yielding in the temperature range of 600-750 °C, which is most possibly attributed to the very weak interaction between Mo atoms and mobile dislocation as a result of precipitation. Although aging for 36 h at 870 °C decreased the tensile ductilities of this alloy below 600 °C, the aged alloy showed the absence of ITE and higher yield strength in comparison with solutionized alloy. The tensile ductilities in the aged alloy were insignificantly affected by increasing the temperature until 700 °C, beyond which the tensile ductilities were found to increase drastically with temperature.