Search the site

The University of Manchester Library

In April 2016 Manchester eScholar was replaced by the University of Manchester’s new Research Information Management System, Pure. In the autumn the University’s research outputs will be available to search and browse via a new Research Portal. Until then the University’s full publication record can be accessed via a temporary portal and the old eScholar content is available to search and browse via this archive.

An Investigation into the Texture Development during Hot-Rolling of Dual-Phase Zirconium Alloys

Daniel, Christopher

[Thesis]. Manchester, UK: The University of Manchester; 2018.

Access to files

Abstract

Dual-phase alpha plus beta Zr-Nb alloys have a higher strength and fracture toughness than single-phase alpha alloys and develop different crystallographic orientations (textures) during thermo-mechanical processing. The textures developed at manufacture are particularly important in determining the life-limiting in-reactor behaviour of nuclear components. Dual-phase Zr alloys tend to form a strong transverse (TD) texture of the basal pole, the origin of which is poorly understood and cannot be predicted by crystal plasticity texture evolution models. This is because the microstructure and texture evolution of these dual-phase alloys arises from complex interactions between the alpha (hexagonal-close-packed, hcp) and beta (body-centred-cubic, bcc) phases, during both deformation and phase transformation. The work presented here is an investigation of the texture evolution during high temperature rolling of an industrially used Zr-2.5Nb alloy, along with the hot-rolling and uniaxial compression of two model dual-phase Zr-Nb alloys (Zircaloy-4 with 2.5 wt.% Nb and Zircaloy-4 with 7 wt.% Nb). The aim was to determine the relative roles of plastic strain partitioning between phases, the activity of the different deformation modes and phase transformation on the final texture. The effect of temperature (700C to 825C), reduction ratio (50% to 87.5%) and strain rate, along with the influence of starting texture, was characterised using time-of-flight (TOF) neutron diffraction and EBSD techniques. The alpha transverse texture component, with prismatic alignment {11-20}<10-10>, strengthens with greater rolling reduction at the higher temperatures, accompanied by a weakening of basal part orientations with 0002 in ND. Software reconstruction of EBSD orientation maps, using the Burgers relationship, shows how the strength of the transverse texture component varies across the material depending on the orientation of large prior-beta grains. A more detailed characterisation of the high temperature deformation and phase transformation behaviour was made on a hot-rolled Zircaloy-4 with 7 wt.% Nb alloy. Since a greater proportion of metastable beta-Zr is retained to room temperature, a snapshot of the material before beta to alpha phase transformation can be captured, distinguishing high temperature primary alpha grains from the nucleation and growth of secondary alpha variants. By analysing these structures in 3D, using a plasma focused ion beam (PFIB) and taking sequential EBSD slices, it was found that the degree of breakup is affected by the distribution of primary alpha laths within each beta-grain. Further analysis shows that the orientation of the primary alpha influences the breakup behaviour of the beta-grains. Softer alpha orientations, with 0002 in TD, are favoured through a slip compatibility with the beta-matrix. Harder alpha grain orientations develop a much higher misorientation, with a greater stored energy to undergo a dynamic transformation, during deformation. These findings suggest new ways in which the current models can be developed, to enable the successful prediction of hot-rolling textures in these alloys.

Bibliographic metadata

Type of resource:
Content type:
Administered thesis
Form of thesis:
Alternative format
Type of submission:
Doctoral level ETD - final
Thesis title:
An Investigation into the Texture Development during Hot-Rolling of Dual-Phase Zirconium Alloys
Degree type:
Engineering Doctorate
Degree programme:
EngD Materials
Publication date:
2018-05-14T12:28:29
Institution:
The University of Manchester
Location:
Manchester, UK
Total pages:
371
Abstract:
Dual-phase alpha plus beta Zr-Nb alloys have a higher strength and fracture toughness than single-phase alpha alloys and develop different crystallographic orientations (textures) during thermo-mechanical processing. The textures developed at manufacture are particularly important in determining the life-limiting in-reactor behaviour of nuclear components. Dual-phase Zr alloys tend to form a strong transverse (TD) texture of the basal pole, the origin of which is poorly understood and cannot be predicted by crystal plasticity texture evolution models. This is because the microstructure and texture evolution of these dual-phase alloys arises from complex interactions between the alpha (hexagonal-close-packed, hcp) and beta (body-centred-cubic, bcc) phases, during both deformation and phase transformation. The work presented here is an investigation of the texture evolution during high temperature rolling of an industrially used Zr-2.5Nb alloy, along with the hot-rolling and uniaxial compression of two model dual-phase Zr-Nb alloys (Zircaloy-4 with 2.5 wt.% Nb and Zircaloy-4 with 7 wt.% Nb). The aim was to determine the relative roles of plastic strain partitioning between phases, the activity of the different deformation modes and phase transformation on the final texture. The effect of temperature (700C to 825C), reduction ratio (50% to 87.5%) and strain rate, along with the influence of starting texture, was characterised using time-of-flight (TOF) neutron diffraction and EBSD techniques. The alpha transverse texture component, with prismatic alignment {11-20}<10-10>, strengthens with greater rolling reduction at the higher temperatures, accompanied by a weakening of basal part orientations with 0002 in ND. Software reconstruction of EBSD orientation maps, using the Burgers relationship, shows how the strength of the transverse texture component varies across the material depending on the orientation of large prior-beta grains. A more detailed characterisation of the high temperature deformation and phase transformation behaviour was made on a hot-rolled Zircaloy-4 with 7 wt.% Nb alloy. Since a greater proportion of metastable beta-Zr is retained to room temperature, a snapshot of the material before beta to alpha phase transformation can be captured, distinguishing high temperature primary alpha grains from the nucleation and growth of secondary alpha variants. By analysing these structures in 3D, using a plasma focused ion beam (PFIB) and taking sequential EBSD slices, it was found that the degree of breakup is affected by the distribution of primary alpha laths within each beta-grain. Further analysis shows that the orientation of the primary alpha influences the breakup behaviour of the beta-grains. Softer alpha orientations, with 0002 in TD, are favoured through a slip compatibility with the beta-matrix. Harder alpha grain orientations develop a much higher misorientation, with a greater stored energy to undergo a dynamic transformation, during deformation. These findings suggest new ways in which the current models can be developed, to enable the successful prediction of hot-rolling textures in these alloys.
Keyword(s):
Thesis main supervisor(s):
Thesis co-supervisor(s):
Funder(s):
Degree grantor:
Language:
en

Institutional metadata

University researcher(s):
Academic department(s):

Record metadata

Manchester eScholar ID:
uk-ac-man-scw:314538
Created by:
Daniel, Christopher
Created:
14th May, 2018, 11:28:29
Last modified by:
Daniel, Christopher
Last modified:
3rd June, 2019, 11:00:41

Can we help?

The library chat service will be available from 11am-3pm Monday to Friday (excluding Bank Holidays). You can also email your enquiry to us.