Micromechanics Group - News

#EBSD2018 - UK and USA meetings
Enjoyed attending both the RMS EBSD2018 meeting in the UK, and the MAS one in the USA this year. It is impressive that new analysis approaches and continual refinement of existing methods are still pushing the technique on at pace. The information we can extract from these patterns is extraordinary and the range of applications continues to astound and grow. Very pleased that Oxford Micromechanics Group and our collaborators were able to contribute to these two vibrant meetings.

[4 June 2018]
Front Cover of Journal of Microscopy
Have belatedly realised our work was on the front cover of Journal of Microscopy in Septmeber last year. The front cover image shows dislocations threading through a GaN layer grown from a patterned substrate. The dislocations are revealed through channelling contrast using signal integrated from the low take-off angle region of an array of EBSD patterns. The paper describes how images revealling different features of the sample can be generated from the stack of EBSD patterns. The microscopy and data collection was carried out by Arrantxa Vilalta-Clemente while Aimo Winkelmann (Bruker Nano) analysed the data and rendered the images

[27 January 2018]
JMicroscopy front cover
Microcantilever video 3D

Post-Doc position with Ed Tarleton
Ed Tarleton is currently seeking a talented researcher to join his growing team of micromechanical modellers. The post holder will work on an exceiting Discrete Dislocation Dynamics project within the MAINTAiN programme (Multi-scAle INTegrity assessment for Advanced high-temperature Nuclear systems).
The application deadline is 19th February - see here for further details

[21 January 2018]
3D-XRD study published in Nature Comms
High value hexagonal alloys Ti and Zr are used in safety critical applications in the aerospace and nuclear industries. Understanding and improving their performance requires untangling the complex patterning of stress and strain at the microstructural level. The MicroMechanics Group has used 3D-X-ray Diffraction, coupled with crystal plasticity FEM simulations, to study stress evolution across thousands of contiguous grains in polycrystals loaded in situ at the ESRF ID11. Large anisotropy in elastic stiffness, thermal expansion and plastic flow stress in these materials ensure that the local grain neighbourhood has a profound effect on stress development in any particular grain. Indeed the neighbourhood effect is so strong that for many grains the stress level can actually drop despite the global stress state increasing during tensile plastic flow.
The work is available in Nature Communications.

[13 January 2018]

DMC cruciform

Dave Collins moves to Lectureship at Birmingham
After 5+ years with the Micromechanics Group David has moved to the University of Birmingham as a Birmingham Fellow and Lecturer. While with the Micromechanics Group David carried out some great work on biaxial deformation of steels and effects of strain path changes on ductility, and more recently contributed to the HexMat programme grant using HR-EBSD to study cold dwell effects in Ti alloys. He will still be seen around the Department as an Academic Visitor and we hope to continue lasting collaborations with him.
We wish him well in setting up his own research group. [note he has a PhD project available].

[7 January 2018]
Junnan Jiang - DPhil Viva
Junnan Jiang submited his doctoral thesis in October, and we are delighted that he came through his viva voce examination in December. His thesis concerns grain boundary sliding and superplasticity/creep in Sn-Bi. highlights were micro-mechanical testing of sliding at individual isolated grain boundaries and the first 3D observations of grain neighbour switching in the interior of a sample using diffraction contrast tomography. Junnan is now finalising and agreeing minor corrections to his thesis. Congratulations Junnan!

[6 January 2018]


Experiment at JEEP -Diamond Light Source
The group recently spent 3 days at the JEEP beamline, Diamond Light Source. Yi Xiong, and Christopher Megazzini worked hard, guided by Phani Karamched, to get samples ready in time for these experiments. We were joined at JEEP by David Collins (now at Birmingham), and Chi-Toan Nguyen (Manchester) who brought knowledge of the ETMT equipment. As ever support at JEEP was excellent - our thanks to Robert Attwood and Stefan Michalik. The team successfully ran a series of in situ stress relaxation tests on Ti alloys - data analysis is now underway...

[4 January 2018]
Post-Doc Positions Available
We currently have 2 post-doc positions available and are seeking talented and highly motivated researchers with background in nuclear materials. The first post concerns characterisation of radiation damage as part of the EPSRC platform grant awarded to the Materials for Fusion and Fission Power group in the area of Advanced Nuclear Materials. The second is to work on a project lead by David Armstrong on Radiation Resistant High Entropy Alloys. This post is funded by the EPSRC in the UK and is part of a wider NEUP program funded by the DoE in the USA and lead by the University of Wisconsin-Madison.

[7 September 2017]

Hamid A

Hamid Abdolvand - starting new group at Western
Hamid Abdolvand is about to take up an Assistant Professorship at the Western University, Ontario. We wish him every success as he begins the exciting task of setting up the Multi-Scale Deformation Lab in the Department of Mechanical and Materials Engineering, and look forward to continuing collaboration over the coming years.

[17 December 2016]
Yuanbo Tang - Prizes
Yuanbo Tang was in Tokyo in August for the 4th UK-Japan Engineering Eduction League Joint Workshop. This was hosted by Prof Kikuo Kishimoto at Tokyo Tech's Ookayama Campus. Yuanbo gave a great 3 minute pitch for his work on grain boundary serration and talked enthusiastically about his work to all who dropped by his poster. He was award the Best Poster prize for his troubles. Earlier in the year Yuanbo was awarded a William R Miller Postgraduate Award by his college St Edmund Hall.

[4 September 2016]
Yuanbo Prize
Hong Kong1
Hong Kong2
Building Bridges in Hong Kong
Dave Collins and Ed Tarleton spent a week at the Chinese University of Hong Kong running a Material Science course in a summer school organised by St Anne’s College. The summer school ran for 4 days, selecting 16-year old students local to Hong Kong. The Materials day was attended by a total of 100 students. The hands-on activities they organised by Ed and Dave included building bridges using lollipop sticks, then testing them to fracture- some of them weighing just 100g were strong enough to withstand 20kg! The students also got to see how Materials Science is important to sound devices, building and testing speakers, then examining resonance effects and standing wave patterns in a vibrating Chladni plate.

[5 August 2016]
Advanced Nuclear Materials Platform Grant
EPSRC have awarded a 4 year, £1.3M Platform Grant to the Materials for Fusion and Fission Power team led by Prof Steve Roberts. Grant activities span across processing, characterisation, and properties of advanced structural materials for applications in nuclear fission and fusion reactors. Micromechanics will be a key aaspect of the work especially in examining the irradiation response of key materials. The funding will support early-career postdoctoral researchers (ECRs) in a flexible manner tailored to their individual career trajectories, resources for mentorship, opportunities for new skills training, and allow ECRs to develop their own research ideas.

[31 July 2016]
MFFP Group
Which way is up?
We have lost count of the number of person hours we have spent making sure that reference frames are correctly understood and described. This is absolutely vital for successful comparison of data between experiments, say EBSD and X-Ray DAXM or 3DXRD, and of course for transferring information to crystal plasticity simulations. Its seems like every time we setup a new instrument or go to a synchrotron beamline we haven't used before we have a slightly unsettling period while we establish and gain confidence that we have the important reference frames properly pinned down. Last time we went through this proces with EBSD kit in our labs we decided to write down the procedures in some detail. As we can't possibly be the only ones facing these issues we have shared our approach by publishing it (open access) in Materials Characterization. Hopfully this might be a useful resource to other groups and we would certainly welcome any feedback and/or approaches in use elsewhere. Establishing best practice on this is in everyones interest.

[26 May 2016]
Ed Tarleton Awarded EPSRC Early Career Fellowship
Congratulation to Ed Tarleton on the award of his EPSRC Fellowship on Dislocation based modelling of deformation and fracture in real engineering alloys. The five years funding will allow Ed to continue his inovative modelling work. Developing simulations that capture the rich and complex interactions between, dislocations, diffusion, precipitate formation and fracture is central to Ed's work. Such capabilies are vital for us to maximise the understanding and therefore impact of many of the experimental programmes within the Micromechanics group. Ed is looking to grow his team in the near future and will be recruiting at both post-doc and doctoral student level.

[6 Nov 2015]
Ed T

DMC Diamond-Infineum award photo

Diamond-Infineum ECR Prize for David Collins
David Collins has been awarded the Diamond-Infineum Early Career Researcher Prize for outstanding work produced using Diamond’s facilities in a research area relevant to the automotive sector. David received the award at the Illuminating Challenges in Automotive Research Conference where he was invited to present his award winning work on in-situ biaxial deformation. Congratulations David - its well deserved.

[5 Nov 2015]
Pair of Acta Materialia Papers on Twinning
Hamidreza Abdolvand has published a pair of papers on deformation twinning in Zircaloy-2. The first paper reports on experimental measurements made at ESRF beamline ID11 using the 3D-XRD method developed by the Riso/DTU group. During an in situ tensile study the method was used to characterise the size, position, orientation and average lattice strain state in grains within a sample volume of ~0.8x0.8x0.9mm. There were a little over 6100 grains in the sample volume a the start of the experiment but after ~2.8% strain twinning meant that the same volume was segmented into over 9700 grains. The progressive increase in lattice strains and amount of twinning was followed using observations at 7 different strain levels. In the second paper results are presented from a large (2600 grain) CP-FEA simulation using a microstructure constructed from the 3D-XRD data. The model captures the twinning well. The stresses in twin and parent gran pairs are examined just after twin formation for both experimental and simulated results. A significant finding is that local normal stresses in the twin and parrent pairs both normal to the twin habit plane and along the twin shear direction are essentially identical.

[23 May 2015]
Hamid A 3DXRD Zr twining

ESRF April 2015 team photo

Experiment at ID11 ESRF
We were fortunate to get allocated 18 shifts (6 days) of beamtime at ID11 ESRF. Hamid Abdolvand who had drafted the proposal led the team consisting of Jicheng Gong, Dave Collins, Yi Guo. Jon Wright (centre of photo) provided tremendous support both in the lead up to the experiment and during it. The team successfully ran a series of 3D XRD measurments during in situ tensile testing of Ti and Zr samples. With help from Wolfgang Ludwig some diffraction contrast tomography scans were also conducted taken at the start and and of the deformation experiments. Hamid will be kept busy with data analysis for a considerable time.

[2 May 2015]
DDD-FEA modelling

DDD-FEA modelling
Ed Tarleton in collaboration with Daniel Balint (Imperial College) have successfully embedded discrete dislocation dynamics simulations of plasticity within a finite element analysis framework that handles complex displacement and traction boundary conditions. This new modelling capability is an important tool for analysis of small scale mechanical testing experiments. Micro-cantilever bend tests on hexagonal Ti and Zr crystals conducted by Jicheng Gong have been simulated. The marked size effect, stochastic flow behaviour, and slip band spacing evident in the experiments are all well captured by the simulations. The study is reported in Acta Materialia

[15 Feb 2015]
Microscopy and Analysis cover
Sample preparation of zirconium alloys for EBSD can be difficult and lack reproducibility. Hamid Abdolvand has been working with a broad ion beam based system, the Precision Etching and Coating System II (PECS II) from Gatan. With help from friends at Gatan he has been able to produce samples that generate high quality EBSD patterns reproducibly over large areas. An example map taken from a highly deformed Zircaloy-2 sample and containing many deformation twins was used as the front cover of the November issue of Microscopy and Analysis.

[30 Dec 2014]
Microscopy and Analysis cover

slip band-GB interaction

DPhil Studentships Available
There are two funded DPhil projects available within the group for October 2015 start. Both concern micromechanical aspects of deformation and fatigue in Ti alloys. The first concentrates on continuing developent and application of small-scale ultrasonic testing for high cycle fatigue. The other will continue a successful vein of work using HR-EBSD and other methods to study slip band – grain boundary interactions. Both projects will involve collaboration with Rolls Royce and link into activiities on the HexMat Programme grant. Unfortunately funding is restricted to UK and EU citizens.
'Further Details'

[14 Dec 2014]
HexMat PDRA Day
Post-Docs working on the HexMat Programme grant gathered at Oxford Materials on 24th-25th September 2014. The research team are : Sudha Joseph, Terry Jun, Bo Lan, Thomas White and Zhen Zhang (Imperial College London), Eleni Sarakinou (University of Manchester), with Hamid Abdolvand and Rajesh Korla hosting from Oxford. This was one in a series of networking events designed to encourage collaboration amoungst the group. Outreach was a central part of this event and Jayne Shaw (Outreach Officer at Oxford Materials) gave an insightful briefing on what makes for good outreach before setting the team a challenge of designing primary school level outreach projects. The day ended with a tour of the department before dinner. The second day started with research talks from the PDRAs which showed strong progress and establishment of good links between team members and institutes. Mitch Cuddihy and Vivian Tong (PhD students form Imperial) joined the meeting and delivered training for the upcoming HexMat/WCSIM (Worshipful Company of Instrument Makers) event in November, London Bridge.
[30 Sept 2014]

HexMat PDRAs at Oxford

Dave Collins at Diamond

InsideDiamond Article
Earlier in the year Dave Collins and his team (Hamid Abdolvand, Mahmoud Mostafavi (Sheffield), Richard Todd and Angus Wilkinson) had beam time at the Diamond Light Source - I12 where they were extremely well supported by Thomas Connolley. The in situ deformation experiment on non-proportional biaxial deformation broke new ground and was very successful. The work caught the attention of a journalist from 'InsideDiamond' who interviewed David during the experiment- their article is on page 15.

New SEM and EBSD system
Our new Zeiss Merlin FEG-SEM and High Resolution Bruker EBSD system have been installed. Arantxa and Hamid are getting to grips with the new instrument with help from Gabriella Chapman and Gareth Hughes in the EM research Support Group. A couple of days in and Arantxa already has some initial images of atomic terraces on GaN surfaces and threading dislocations making up mosiac cells in a thin InAlN film.

atomic steps on GaN mosiac cells in InAlN

New post-doc joins group
Hamidreza Abdolvand has joined the group. He will be working on Hi-Res EBSD within the 'HexMat' programme grant - Heterogeneous mechanics in hexagonal alloys across length and time scales. He has previously worked at Manchester with Phil Withers and was a student at Queens Univesity with Mark Daymond and has experience of crystal plasticity FEA and synchrotron based diffraction methods.

Dave Collins at APS

Successful Experiment at APS
Dave Collins, Ed Tarleton and Ben Britton (Imperial College) had a busy time in Chicago at the Advanced Photon Source (34-ID-E) in November. They returned to the UK with ~6TB of data that they and Yi Guo have now set about analysiing.

Jun Jiang Thesis Submission
Congratulations to Jun Jiang on submitting his DPhil thesis on 'A High Resolution Electron Backscatter Diffraction Study of Heterogeneous Deformation in Polycrystal Copper'. Both data collection and analysis for Hi-Res-EBSD have moved forward enormously through Jun's efforts.