Reducing Emissions by Exploiting Field-Induced Martensitic Transformations
Lead Research Organisation:
Imperial College London
Department Name: Materials
Abstract
The aim of the the fellowship will be to develop the analysis tools to design and use materials that exploit stress- and electromagnetic field-affected phase transformations. This area extends from bainite and martensite in steels to the variant selection problem during the beta->alpha transformation in titanium and zirconium alloys, from omega superelasticity in the beta-Ti alloy GUM metal to NiTi shape memory alloys (SMAs) and ferromagnetic SMAs. In the component context, conventional SMAs rely on a temperature change to provide actuation, which is achieved either passively in response to the environment or by heating / cooling using bleed air, resistance heating or heating filaments. Ferromagnetic SMAs use an electromagnetic field, which allows much faster switching, for example in a pump or to improve flow control. While the crystallography of these transformations is well understood, models are not generally available for the micromechanics that can be incorporated into Finite Element (FE) descriptions of component behaviour used by designers. In addition, whilst these systems are clearly tractable to atomistic approaches, atomistic modeling is still too immature to reliably design new alloys without experimental support; however approaches such as density functional theory (DFT) can enable insight into alloy design approaches to be developed. A subsidiary aim will be to start to bridge the gap to the DFT community. In conventional alloys the problem is often complicated by a diffusional component to the transformation, or nucleation may be the limiting step. However, we have recently shown clearly that applied stress can bias variant selection, leading to the production of mono-variant transformed beta grains in Ti-6246, with consequent effects on properties. The ability to model variant selection in diffusionless transformations, such as in martensite in steels, omega in Ti and Zr, and in (f)SMAs will be a prerequisite to modeling the more complicated problem in Ti-64 and Ti-6246. Industrially, the major goal of the fellowship will be to build a capability to model such transformations and to design alloys exploiting them for use in aerospace, automotive and power applications, with QinetiQ, Rolls-Royce, Timet, Corus and DSTL.
Organisations
- Imperial College London (Lead Research Organisation)
- Rolls Royce Group Plc (Collaboration)
- Rolls-Royce (United Kingdom) (Project Partner)
- Defence Science and Technology Laboratory (Project Partner)
- Corus (Project Partner)
- Qinetiq (United Kingdom) (Project Partner)
- Titanium Metals Corporation (United Kingdom) (Project Partner)
Publications
Azeem M
(2014)
In situ evaluation of the transformation behaviour of NiTi-based high temperature shape memory alloys
in Intermetallics
Azeem M
(2017)
Functional stability of a ferromagnetic polycrystalline Ni2MnGa high temperature shape memory alloy
in Scripta Materialia
Azeem M
(2015)
Lattice instability during the martensitic transformation in the high temperature shape memory alloy Zr(Cu0.5Co0.25Ni0.25)
in Journal of Alloys and Compounds
Bhowmik A
(2016)
Using coupled micropillar compression and micro-Laue diffraction to investigate deformation mechanisms in a complex metallic alloy Al13Co4
in Applied Physics Letters
Béreš M
(2015)
Effect of variant transformations in fusion zones of gas metal arc welds
in Science and Technology of Welding and Joining
Chapman T
(2015)
Characterisation of short fatigue cracks in titanium alloy IMI 834 using X-ray microtomography
in Acta Materialia
Chapman T
(2015)
Environmentally assisted fatigue crack nucleation in Ti-6Al-2Sn-4Zr-6Mo
in Corrosion Science
Chapman T
(2015)
The Dislocation Mechanism of Stress Corrosion Embrittlement in Ti-6Al-2Sn-4Zr-6Mo
in Metallurgical and Materials Transactions A
Coakley J
(2017)
Microstructural evolution in a superelastic metastable beta-Ti alloy
in Scripta Materialia
Coakley J
(2016)
Isothermal omega formation and evolution in the Beta-Ti alloy Ti-5Al-5Mo-5V-3Cr
in Philosophical Magazine Letters
Coakley J
(2012)
Lattice strain evolution in a high volume fraction polycrystal nickel superalloy
in Scripta Materialia
Coakley J
(2016)
Effect of precipitation on mechanical properties in the ß-Ti alloy Ti-24Nb-4Zr-8Sn
in Materials Science and Engineering: A
Coakley J
(2017)
Isothermal omega kinetics in beta-titanium alloys
in Philosophical Magazine Letters
Coakley J
(2018)
Characterizing nanoscale precipitation in a titanium alloy by laser-assisted atom probe tomography
in Materials Characterization
Coakley J
(2015)
Precipitation processes in the Beta-Titanium alloy Ti-5Al-5Mo-5V-3Cr
in Journal of Alloys and Compounds
Davies C
(2014)
The Influence of Pre-existing Deformation on GMA Welding Distortion in Thin Steel Plates
in Journal of Materials Engineering and Performance
Dye D
(2015)
Shape memory alloys: Towards practical actuators.
in Nature materials
Dye D
(2014)
Characterization of Phase Transformations and Stresses During the Welding of a Ferritic Mild Steel
in Metallurgical and Materials Transactions A
Evans C
(2012)
The effect of deformation mechanisms on the high temperature plasticity of Zircaloy-4
in Journal of Nuclear Materials
Jones N
(2011)
Martensite evolution in a NiTi shape memory alloy when thermal cycling under an applied load
in Intermetallics
Jones N
(2013)
Influence of applied stress on the transformation behaviour and martensite evolution of a Ti-Ni-Cu shape memory alloy
in Intermetallics
Knop M
(2014)
A New Polycrystalline Co-Ni Superalloy
in JOM
Martin T
(2016)
Insights into microstructural interfaces in aerospace alloys characterised by atom probe tomography
in Materials Science and Technology
Meher S
(2012)
Solute partitioning and site preference in ?/?' cobalt-base alloys
in Scripta Materialia
Obbard E
(2011)
The effect of oxygen on a? martensite and superelasticity in Ti-24Nb-4Zr-8Sn
in Acta Materialia
Description | Shear at the microscopic scale is often exploited, or a degradation mechanism in, the metallic materials that power our world. In zirconium in nuclear reactors, brittle hydrides are precipitated during cooling - in this work we have shown for the first time using sub-micrometre X-ray beams, that these hydrides can plastically deform in a microstructure, which helps us start to unpick how they embrittle spent nuclear fuel can. In shape memory alloys, we now understand how these materials degrade during repeated actuation, by accumulating defects at the interfaces of the shearing phase that provides the shape change. We also understand how to tailor that interface such that these defects do not accumulate, providing a roadmap for cyclically stable actuator alloy development, opening up real engineering uses for these materials. In biomedical and superelastic titanium alloys, which excite much currency interest in the community, we were able to identify that these alloys are not thermally or mechanically stable, but can be used as damping materials - a sort of metallic rubber. Again, the interface plays a key role, as does aluminium, providing possibilities to develop these alloys further for stability and thence, large scale application. In titanium alloys in jet engines, we were able to resolve a stress corrosion cracking problem - again, one involving hydrogen embrittlement, and retire over £50m/yr worth of cost to Rolls-Royce. |
Exploitation Route | The materials development activities have shown how superelastic and twinning alloys deform, contributing to the development of TWIP steels (current UK MOD / Tata / Timet program), to our understanding of superelastic and shape memory materials (e.g. Nature Materials invited comment), and to the scope of applicability of these materials (e.g. to jet engines with Rolls-Royce). |
Sectors | Aerospace, Defence and Marine,Healthcare,Manufacturing, including Industrial Biotechology,Security and Diplomacy,Transport |
Description | Rolls-Royce have evaluated the use of superelastic beta-Ti alloys for use in jet engines; we concluded that the existing alloys had some problems that prevent their adoption but that the underlying concept is sound. One of the PhDs in this programme resulted in some pathways to develop alloys that avoid these problems. Much of the work in this programme around oxygen levels has resulted in the development of a technique for measuring oxygen levels in titanium surfaces, which been critical to resolving some significant service issues, saving >£40m in 2015 alone. The TWIP steels work is currently resulting in scale-up work with Tata steel to develop a new automotive opportunity for them. The zirconium hydrides work has been useful to supporting Rolls-Royce submarines' understanding of how these materials behave in service. |
First Year Of Impact | 2014 |
Sector | Aerospace, Defence and Marine |
Impact Types | Economic |
Description | EPSRC Programme Grant (Hexmat) |
Amount | £4,979,741 (GBP) |
Funding ID | EP/K034332/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 05/2013 |
End | 05/2018 |
Description | EPSRC Programme grant (DARE) |
Amount | £3,226,486 (GBP) |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 09/2014 |
End | 09/2019 |
Description | SPII |
Amount | £7,939,564 (GBP) |
Funding ID | EP/M005607/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 10/2014 |
End | 09/2019 |
Description | Rolls-Royce plc |
Organisation | Rolls Royce Group Plc |
Country | United Kingdom |
Sector | Private |
PI Contribution | . |
Collaborator Contribution | . |
Impact | . |