Abstract
The high temperature mechanical behaviour of nickel base superalloys depends mainly on the reinforcing γ' precipitate volume fraction and on its morphology that evolves significantly during deformation particularly at high temperature. In single crystal nickel base superalloys characterised by negative misfit between γ' and the γ phases, the original cuboidal γ' microstructure develops into a lamellar γ/γ' pattern perpendicular to the loading axis, when the alloys are crept at high temperature under tensile load along a <001> crystallographic direction. The typical creep curves of nickel base superalloys are characterised by three or four different creep stages. Such stages can be rationalised in terms of evolution of the reinforcing γ' phase morphology during creep. The aim of this paper is to investigate the effects of γ' morphology evolution on the long tertiary creep behaviour of the nickel base superalloy SMP 14 at 1000 °C.

Key words
creep, single crystal nickel base superalloy, microstructure

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