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Effects of microstructure and strain ageing on toughness of nuclear PWR reactor weld metals

Farron, Victoria Jane (2010)
Ph.D. thesis, University of Birmingham.

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Abstract

The effects of microstructure and prestraining and ageing on ductile-to-brittle transition temperature, fracture toughness and cleavage fracture resistance of a multi-pass low-alloy ferritic steel weld metal have been investigated. The weld metal simulated submerged arc welds used in the fabrication of Sizewell B power station reactor pressure vessel. The study aimed to investigate differences in mechanical properties of a single microstructure; asdeposited and reheated microstructures and subjected to various mechanical tests. Additionally, to simulate the effects of irradiation embrittlement a number of specimens were prestrained and then statically strain aged. Charpy impact transition curves had obvious trends depending upon microstructure and condition, with microstructure having a significant influence on the transition region and upper-shelf impact energy level. Prestraining and ageing the specimens promoted an increase in the ductile-to-brittle transition temperature and reduction the upper shelf energy level for both microstructures. The extremes of behaviour were defined by the reheated as-received and as-deposited prestrained and aged conditions, being the “best” and “worst conditions” respectively. This trend was repeated with the cracktip opening displacement tests. A combination of factors decreases toughness for the asdeposited prestrained and aged condition, which exhibited the highest yield stress, and lowest work hardening exponent and the best cleavage fracture resistance. Such factors result in marked upwards shifts in Charpy impact transition curves and decease in the crack growth resistance curves.

Type of Work:Ph.D. thesis.
Supervisor(s):Bowen, Paul
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Subjects:TK Electrical engineering. Electronics Nuclear engineering
Institution:University of Birmingham
ID Code:1114
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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