Details of Grant 

EPSRC Reference:	GR/R68863/01
Title:	The structure and evolution of copper-rich precipitates in ferritic steels and their role in hardening
Principal Investigator:	Jenkins, Dr M
Other Investigators:	Titchmarsh, Professor J
Researcher Co-Investigators:	Dr A Barashev Dr Y Osetsky
Project Partners:	Argonne National Laboratory INSS Inc Ricardo Group Rolls-Royce Plc University of California, Santa Barbara
Department:	Materials
Organisation:	University of Oxford
Scheme:	Standard Research (Pre-FEC)
Starts:	01 October 2002	Ends:	31 March 2006	Value (£):	225,895
EPSRC Research Topic Classifications:	Materials Characterisation Materials testing & eng.
EPSRC Industrial Sector Classifications:	Energy
Related Grants:	GR/R68870/01
Panel History:	Panel Date Panel Name Outcome 07 Nov 2001 Structural Materials Panel Meeting, November 2001 Deferred
Summary on Grant Application Form
The in-service hardening of nuclear reactor pressure vessels due to copper precipitation is of particular concern. During thermal ageing or electron irradiation the copper precipitates experience nucleation, growth and Oswald ripening, and the hardening passes through a maximum and then decreases. A distinguishing feature of this process is that the precipitate structure follows a complicated sequence bcc-9R-3R-fcc. In contrast, under neutron irradiation the precipitates do not coarsen to sizes greater than -2 nm and hardening is observed to be close to the maximum. Moreover, position-sensitive atom-probe investigations suggest that the precipitates contain a high proportion of iron. However, despite expectation that these precipitates should have a coherent bcc form, we have recently identified a population of precipitates with the 9R structure. The reasons for these observations are unclear. The hardening mechanisms produced by 9R or fcc precipitates are unknown and that by coherent clusters is uncertain. Indeed, our recent molecular dynamics simulations show that the passage of a screw dislocation through a bcc precipitate can trigger the transformation to an fcc form. Thus, the conventionally accepted modulus hardening model may not apply. The Influence of additional alloy and impurity atoms in precipitates is also unknown. The primary aim of the research proposed here is to elucidate the issues above by using a combination of in-situ and ex-situ electron microscopy, and atomic-scale computer modelling.
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