Selective Laser Melting (SLM) induced grain boundary engineering (GBE) strategy

Grain boundary engineering (GBE) has been one of the key methods to improve the surface properties of high-performance alloy materials. Increasing the frequency of coincidence site lattice (CSL) boundaries by GBE was found to optimise grain boundary character distribution, disrupting the connectivity of random boundaries and enhancing the resistance to grain boundary degradation. GBE can be achieved by thermomechanical processes, while some conventional approaches like cold working followed by annealing are not feasible for customised complex components.

In this article, Dong et al. have brought the potential of improving the stress corrosion resistance of selective laser melting (SLM) fabricated components by GBE to light. Co-Cr alloy specimens were fabricated by SLM using the checkboard laser scan strategy and the GBE process was done by annealing at 1200 for 1 h. Through the annealing, a high frequency of twin and twin-variant boundaries was generated from the residual strain stored in the SLM fabricated Co-Cr alloys which interrupted the random boundary networks, improving the crack resistance in 0.9% NaCl solution.

Optical microscope (OM) images of SLM fabricated Co-Cr alloys before (a) and after (d) annealing reveals that the typical fish-scale morphology commonly seen in SLM alloys disappeared and uniform equiaxed grains were formed via GBE. The Kernel average misorientation maps (KAM) show that the residual strain stored in the not annealed specimen (b) is higher than the annealed one (e), which acts as the precursor of the generation of the high frequency of special boundaries through recrystallization. The inverse pole figure (IPF) map of SLM fabricated Co-Cr alloys without annealing (c) shows the preference of <100> and <111> grain orientations along the building direction while randomly distributed orientations are formed after annealing.

 

By comparing these microstructural characteristics of SLM Co-Cr alloys with and without annealing, it’s interesting to see that the effects of GBE are so significant. This study shows the power of engineering microstructures and grains in improving the corrosion resistance of SLM Co-Cr alloys, which is useful for biomedical applications.

If you are interested in more details, please read the original article here.

Dong, Xin, et al. “Grain boundary character and stress corrosion cracking behavior of Co-Cr alloy fabricated by selective laser melting.” Journal of Materials Science & Technology 93 (2021): 244-253.

 

This post was written by Esperanza Shi as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Esperanza is researching the Optimisation of Scanning Strategies for 3D Printed Artificial Joints at Imperial College London, UK.

Mechanical Engineers Walk the Walk – Well Cycle the Cycle!

Absolutely great effort from the School’s Med Tech cyclists Drs Peter Culmer and Andrew Jackson in support of Cancer Support Yorkshire. The route was the famous The Way of the Roses… nice play on words… unifying the pre-eminent counties of England, Lancashire and Yorkshire.

A mighty 250 km cycle across the country in one day!

Please donate on Just Giving: https://www.justgiving.com/fundraising/andrew-jackson112

This post was written by Richard M Hall on behalf of Andrew Jackson and Pete Culmer – Mechanical Engineering, University of Leeds.

Conspiracy theories as new pandemics arise… the role of the scientist!

Word Cloud from a set of Guardian posts on the origins of HIV

While reading the literature for a forthcoming grant submission on aspects of the HIV pandemic, I came across several articles both within and outside the mainstream media that relate to the development and spread of troubling assertions. These concern, for instance, the origin of HIV and an implied role of politicians in restricting or encouraging certain avenues of development to maintain industries’ pre-eminent economic position and profit-making. Sometimes these assertions develop into conspiracy theories which are explained, at a later date, in relatively simple terms, as is the case in recognising HIV sequences in the SARS-Cov-2 virus. Here, a bit more thought and critical evaluation would have prevented this avenue of thought, but instead it was posted on a pre-print server for all to see and then subsequently withdrawn, but not before the ‘engineered’ virus concept had taken hold in certain areas of the media.  The simple explanation was that a number of viruses have these sequences.

So what, as scientists, are we to do about preventing such misrepresentations in terms of engaging the public and our own self-management? Here are some thoughts:

  • Employ the skills that are central to our work as scientists, indeed as researchers more broadly, of checking, validating and providing critical insight to our work.  This is particularly important in the medical field generally, but in pandemics specifically, where there may be a heightened awareness of our own frailty and fear of new pathogens that arise from time to time.
  • Personally, I am concerned by the rise in the production of pre-prints from a niche activity to one that has now become mainstream. I suspect this is motivated by data-driven metrics (citations but also prestige) as well as the ‘first to print’, which may be important in exploiting base technologies. It can be argued, however, that this rapid dissemination of information is key, not only in developing collaborative research, especially in times of a pandemic, but also in allowing the quick development of frameworks and insights that may otherwise take months to generate if the peer-review process had to be adhered to. To protect both the research community and the wider public, servers hosting pre-prints have strengthened their assessment procedures once an article is posted. Nature Cancer provides a more nuanced overview of this issue as does the Lancet.
  • We should take it upon ourselves to assess the risks involved in how we report scientific findings, asking ourselves whether our published work can be misconstrued or misrepresented so as to allow a false discourse to emerge that can create a situation that does more harm than good.  I am not suggesting, in any form, that we should self-censor but there may be better ways of disseminating information to allow a more constructive debate.  A lack of transparency can also lead to a rise in misinformation, although we should endeavour to realise that the relationship between opaqueness, conspiracies and power, in the eyes of the public and other stakeholder groups, is a complex one and there are no easy fixes.
  • Following on from this we should aim to provide the public with timely information (see my second point) that adds to the debate, treats the individual or group with respect and takes out of the communication moralising (our prejudice) about their behaviour or activity. This is a multidisciplinary arena which works most effectively when it engages people from different disciplines and stakeholder groups to develop strategies relevant to the target cohort(s).
  • Words (and deeds) matter – choose your words carefully and have consideration for the cultural as well as scientific aspects of the cohorts’ living status.  Using certain words and phrases, however well meaning, can alienate, disenfranchise, further stigmatise and evoke distrust in the individuals or groups we are trying to help.  This applies across a range of illnesses and traumas, but particularly so for those in which there is significant stigma, such as mental health and HIV. In doing so, and where you can, try to make it a two-way dialogue and place the person we are trying to help at the centre of the research – co-create and co-produce – and ensure their contribution is valued.

Those outside science, medicine and research also have responsibilities, especially those that are in positions which require them to uphold given behaviour and adhere to certain protocols or codes of conduct. This is particularly important when using frameworks to build trust between stakeholders in the public at large and the wider concept of ‘truth’.

These are just a few thoughts and are not meant to be definitive answers. But I do hope to stimulate some debate.

10 ingredients for a successful supervisor/PhD student relationship – A thoughtful commentary from Elsevier Connect

The PhD candidate-Supervisor Relationship is probably the cornerstone of academic research, at least in Western Europe. The relationship, which can last anything from 3 to 5 or more years depending on the type and location of the PhD degree, provides a key transition for the student from being a learned individual to one who enhances these attributes and becomes more or less independent in their pursuit of excellence.

Some of the more successful relationships last a lifetime particularly for those candidates that continue a career in academia or a similar domain. Prof Torralba declares 10 key constituents for developing this relationship successfully. How do these attributes/features resonate with your experiences as a supervisor or student?


Is it a bird? Yes it is a peregrine!

Leeds doesn’t have a cathedral but nearby Wakefield Cathedral has a funky visitor, which gets attention from over 100,000 fans in 57 countries! A pair of peregrine falcons are currently nesting on top of the cathedral tower and they have their own personal webcam. Therapeutic viewing after a long day contemplating life, the Universe and BioTrib.

Stop Press – 24 hours later:  Judith tells me there are also Peregrines located on the Parkinson Tower at the University of Leeds.