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Abhinav Priyadarshi is originally from India. He joined Oxford Brookes in September 2018 and the title of his thesis is ‘Influence of ultrasonic melt treatment on the fragmentation of primary intermetallics in Al based alloys’.
I first came to know about Oxford Brookes University through a list of recommended universities across Europe at which to pursue a doctoral degree in the field of mechanical and material sciences, displayed on my ResearchGate profile. One of the faculty members of the University had posted an announcement regarding a PhD position for the UltraMelt2 project. Apparently, the previous version of this project i.e. UltraMelt was very successful with numerous research publications and noteworthy contribution from the research faculty of Oxford Brookes University and other team members.
The PhD project at Oxford Brookes University seemed interesting and was aligned very closely to my educational background and previous work experiences. Moreover, the research area of project UltraMelt2 is one the most promising and emerging fields in the metal industry at present, funded by EPSRC. This project funding was in collaboration with two other leading UK universities and three industrial partners. Also, I came to know that Oxford Brookes University has a very strong industrial collaboration which would significantly help me in my career development. And last but not the least, it would be an opportunity of a lifetime to study in the ‘city of dreaming spires’.
Before coming to UK, I was in Germany as a DAAD funded scholar student from the Indian Institute of Technology Roorkee, India and was carrying out my Master’s thesis work at the Leibniz Institute of Solid State Materials Research, Dresden.
It was quite easy for me to settle in the research environment as the members of the research group were very sociable and responsive. My supervisors and other friends from India have been very supportive to me allowing me to get very comfortable with the surroundings. I am very much overwhelmed with the help received from the International Student Advice Team and the Research Degrees Team for all the resources, and the Doctoral Training Program sessions and various other researcher training induction programmes. I am very much satisfied with the facilities provided to research students at Brookes. The technical staff in the department are very compliant to the requirements of research students to conduct high quality research. The library and the online resource facilities such as IT services are very active at all times and respond to the demands of research students almost immediately.
Our use of metals is so important that it defines periods of human civilization – from the Bronze Age (3600 BC) to the Iron Age (1100 BC). With our present-day mastery of metals and alloys, the mounting emphasis is now on resources and the environment. The metal industry is looking at new ways to produce lighter, stronger materials in a sustainable, economical and pollution-free manner. Ultrasonic melt treatment (UST) is one such green alternative way to a range of conventional melt processes that embraces these goals. UST introduces high intensity ultrasonic waves into liquid metal to induce acoustic cavitation. Laboratory tests show that UST offers beneficial effects: accelerated diffusion, activation of inclusions, improved wetting, dissolution, cluster breakup, and dispersion of particles. UST has a great potential to significantly improve the properties of metallic materials; with benefits of melt degassing, improved wetting of inclusions, enhanced heterogeneous nucleation, refined as-cast structure, and the deagglomeration and dispersion of reinforcing and grain-refining particles. UST and the resulting production of high-quality light alloys are of great interest to the casting, automotive and aerospace industries (viz. accelerated research currently ongoing in China and the USA). UST adds value to manufacturing by environment-friendly melt degassing without the need for either polluting (Cl, F) or expensive (Ar) gases, also eliminating complex processing steps such as fluxing, and by reducing demand for expensive grain refinement additives (Ti, B). Regardless of the beneficial outcome, allocation of this favourable expertise to industry has been flooded by problems, specifically in modifying large amounts of liquid metal typical in methods for instance 'Direct Chill (DC)' continuous casting for ingot making. A shift to efficient continuous processing of large melt volumes as needed by the industry, as well as the possibility for the industry to adopt and adapt this technology, requires the development of validated computer simulation tools based on the experimental gathered data.
To determine the optimum parameters for continuous melt treatment relevant to industrial applications, the proposed project endeavours to develop a quantified experimental description of the ultrasonic melt processing, with a particular focus on the interaction between cavitating bubble structures and solid or gaseous phases typically present in the melt. The research hypothesis is that cavitation bubbles generated by the ultrasonic source have a triple role: implode and generate new bubbles (multiplication), grow and absorb hydrogen from Al melt (degassing), and mechanically interact with solid crystals and inclusions facilitating heterogeneous grain nucleation and refinement (we consider cavitation-induced homogeneous nucleation as irrelevant to real solidification). These effects can be translated to large melt volumes through continuous UST in the melt flow based on the two principle observations made in UltraMelt, i.e. the cavitation bubbles are advected downstream still being within the ultrasound field and the flow management through strategically placed baffles in a launder enlarges the areas of high acoustic pressure.
The metal industry holds the fourth place in sales value among the UK manufacturing industries, representing 7.0 % of the total product sales in 2014, amounting to £25.4 billion. 97% of all metal products manufactured require at least one melting and solidification processing stage, this shows how important it is to understand and control the structures that evolve in solidifying metals, alloys and their composites. After iron, aluminium - the melt of interest in this research - is the most important structural metallic material. This research will open the pathway to the design of more efficient processes that can produce lighter and stronger metallic materials on the industrial scale. The impacts of this research on the environment and society include fuel economy and reduced emissions with the advent of recyclable lighter stronger materials, energy and emissions reduction in the processes involved and avoiding the use of polluting and contaminating fluxes, gases and refiners in manufacturing.
Until the recent research outcomes of our collaborators Brunel University and University of Greenwich via a number of related projects (UltraMelt, UltraCast and ExoMet), only few ex situ and in situ quantified studies of ultrasonic melt treatment in the metallic melt had been reported. Acoustic spectra and pressures were for the first time measured in the aluminium melt in Brunel University with an advanced calibrated high temperature cavitometer. The effects of various factors (operating temperature, transducer power, and distance from source) were quantified. Using particle-image velocimetry (PIV) and high-speed imaging, the acoustic streaming and cavitation profiles in different liquids were characterised and the behavior of liquid aluminium under sonication was inferred by dimensional analysis. Water was found to be a suitable transparent analogue to liquid aluminium for studying acoustic cavitation. High speed and high-energy X-ray imaging (in collaboration with Manchester, Oxford, Hull, DLS) enabled the observation and quantification of cavitation bubble dynamics and sonocapillary effect, and the effects of nano-particles on cavitation development. A unique technique was developed in Brunel University allowing in situ observation of intermetallic fragmentation by cavitation bubbles. Numerous ex situ studies confirmed the effects of UST on degassing, structure refinement, and particle dispersion. On the technological level, proof-of-concept experiments at Brunel University supported the promising scheme of UST in the melt flow. The proposed plan of work further advances these experimental techniques to the industrially relevant phenomena of crystal fragmentation, particle deagglomeration, and ultrasonic processing in the melt flow, providing both a greater insight into the fundamental mechanisms and the validation of the developed models.
With the continuous evolution of science and technology, research may have become a challenging task, but all the hard work that helps you appreciate the amount of work involved in the innovation and discoveries and also makes you feel honoured to be contributing towards humankind. Being a research student takes you beyond classroom knowledge and allows you to think more critically, deeply, ingeniously and independently, which not only helps to expand the horizons of human knowledge, but also helps you to grow as an individual. It also helps in building a professional network with people across the globe.
It has been 5 years now since I entered into the research discipline. Challenges in research are inevitable and are bound to be present. It all depends on how well you manage and execute your objectives. The major challenge for a research student is to first obtain meaningful data from the work/experiments and then to justify your findings with some concrete explanation. Publishing work and articles in renowned journals is another big challenge that many researchers face, and the best way to overcome this challenge is through a comprehensive literature survey. It is important to have a significant amount of background literature knowledge on the proposed area in order to comprehend, accomplish and articulate your novel methodology. It’s as simple as that.
I have found it very worthwhile attending the various research student training sessions at Oxford Brookes. The training provides understanding of research integrity i.e. rigour, ethics, transparency and contribution of others while carrying out research work in different areas. The training is especially useful for people who have just entered into the research environment.
The training has allowed me to look into various stages of research work with an unbiased approach and to understand the intricacies of the same through proper management and planning. I truly believe that attending these research training programmes will always give you some sort of moral and intellectual support to undertake work in a more useful way.
After completing my doctoral degree, I intend to work in an industrial research sector wherein I can put my knowledge and skills to develop something new that can directly or indirectly benefit humankind, gain different experiences and professional knowledge, and ultimately I would like to attain a leadership role somewhere in the metal industry. I also wish to be able to extend my technical expertise and offer help to other deprived sections of society through social services.