Authors: Bertrand Max Bernard Viguier Eric Andrieu Jean Marc Cloue
Publish Date: 2014/08/14
Volume: 45, Issue: 12, Pages: 5431-5441
Abstract
In Alloy 718 a sharp transition exists in the fracture path changing from an intergranular brittle mode to a transgranular ductile mode which is associated with a transition of flow behavior from smooth in the dynamic strain aging regime to a serrated one in the PortevinLe Chatelier PLC regime In order to better understand both deformation and rupture behavior PLC phenomenon in a precipitationhardened nickelbase superalloy was carefully investigated in a wide range of temperatures 573 K to 973 K 300 °C to 700 °C and strain rates 10−5 to 32 × 10−2 s−1 Distinction was made between two PLC domains characterized by different evolutions of the critical strain to the onset of the first serration namely normal and inverse behavior The apparent activation energies associated with both domains were determined using different methods Results showed that normal and inverse behavior domains are related to dynamic interaction of dislocations with respectively interstitial and substitutional solutes atoms This analysis confirms that normal PLC regime may be associated to the diffusion of carbon atoms whereas the substitutional species involves in the inverse regime is discussed with an emphasis on the role of Nb and Mo
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