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Detection of copper precipitates in 15 NiCuMoNb5 (WB 36) steel by using micromagnetic NDE techniques

 
: Dobmann, G.; Altpeter, I.; Szielasko, K.

Bièth, M.:
NDE in Relation to Structural Integrity for Nuclear and Pressurised Components : Sevilla, Spanien, 14.-16.11.2001
Petten, Niederlande: European Commission, 2003
pp.385-387
International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components <3, 2001, Sevilla>
English
Conference Paper
Fraunhofer IZFP ()
copper precipitation; crystal

Abstract
The material investigations presented confirm the results of earlier investigatins with a conclusion that the service-induced hardening and decrease in toughness in WB 36 materials are caused by the precipitation of copper. In the initial state of the material, only a part of the alloyed copper is precipitated. The other part is still solved and can be precipitated during long-term operation at temperatures above 320°C to 350°C.
The copper precipitation leads to a ditortion of the crystal lattice surrounding the copper precipitates and yields internal micro-stresses. If the number and size of the copper precipitates change during operation of a component, a change of the residual-stress level occurs.
The results obained from load stress-related Barkhausen noise measurements demonstrate that these micro-magnetic procedures are generally suitable for the detection of copper precipitation.

: http://publica.fraunhofer.de/documents/N-19895.html