This proposal is submitted in response to the EPSRC Manufacturing the Future Call for Investigator-led Research Projects open on 09 July 2013.

This proposal addresses the urgent need of the metal materials and manufacture industry to search and adopt next-generation, step-change technologies for the manufacturing of primary ingots and/or shaped components with much improved mechanical properties and reliability, less energy consumption and negative environmental impact, e.g. Al and Mg alloys for mass transport applications, consumer products, Ni superalloy for industrial gas turbines (IGTs) for energy generation. At present, our economic competitors are conducting extensive research in this area.

By adopting lighter alloys with better mechanical properties and reliability, mass transport systems can reduce energy consumption, adverse environmental impact, making wider application of alternative fuel schemes possible. While with improved materials performance, IGTs can be operated at a higher temperature duty cycle to increase the efficiency of energy generation.

Casting is one of the most widely used and productive manufacturing technologies for these and other applications. Ultrasonic cavitation treatment offers sustainable, economical and pollution-free solutions to melt processing and casting of conventional and advanced metallic materials with significant improvement in mechanical properties and quality of the products manufactured.

Although demonstrated on a laboratory scale, the ultrasound-assisted casting technique has not yet found widespread industrial application, mostly due to the lack of in-depth understanding of the mechanisms that lead to the macro/microstructure improvement, especially on the mechanisms of enhancing nucleation and crystal multiplication at different stages of solidification processes.

The proposed programme will study the solidification fundamentals of metallic alloys under applied ultrasonic waves, and develop industrial exploitable methodologies to control and optimise the solidified microstructure under the influence of ultrasonic waves. The goal is to realise distinct materials performance improvements in cast products through microstructure refinement, increased chemical and microstructural homogeneity and the reduction of solidification defects in primary ingots and shaped castings.

The proposed research is ambitious and challenging, aiming to study not only the fundamental mechanisms but also to establish practical methodologies of using ultrasound to promote grain nucleation and multiplication during different stages of solidification in metallic alloys.

The novelty of the research is a combination of state-of-the-art in-situ ultra-high speed imaging studies plus advanced numerical modelling and scale-up experiments performed on real metallic alloys.

The outcomes will be new knowledge and novel technological guidelines with their validity demonstrated using commercial alloys and castings produced in the pilot and industrial-scale facilities of the EPSRC Innovative Manufacturing Centre in Liquid Metal Engineering (LiME) and industry partner, Doncasters Group Ltd, providing industry with the knowledge, methodologies and tools to control microstructure of castings using ultrasound technology.

Potential Impact:
The applied methodologies and technical guidelines for control the solidification microstructure using ultrasound developed from this project will provide the industry with novel melt processing and casting technologies to produce metal alloy ingots and/or components with much less energy consumption and adverse environmental impact while with improved mechanical properties and performance that will have direct impact on promoting the competitiveness of the industries in materials manufacture such as primary materials manufacturers, e.g. Alcoa, Novelis, Rio-Tinto-Alcan for Al alloys, Doncasters and Rolls-Royce for Ni superalloy casting and components.

Typical examples include applying the developed technology and guidelines to direct-chill and shape casting to manufacture products with much improved microstructure and reliability, the development of novel metal-matrix composite materials, etc. In addition, the obtained knowledge and models can be used in other research and industrial fields where cavitation is induced in a physico-chemical system. Examples of such systems can be found in many pharmaceutical, biotechnological, chemical, and food industries where ultrasonic devices are currently widely used.

All in all the cavitation-aided melt processing technologies and the manufactured materials enabled by the fundamental knowledge, numerical models and up-scaling methodology gained in this project will contribute to the improvement of the quality of life through environmental sustainability, reduced green-house effect, and the development of new products, and also strengthen the international competitiveness of UK industry.

The benefit gained from the materials manufacture sectors will be passed onto their end users through materials supply chains into many other sectors such as energy, transportation, aerospace, biomedicine, etc. The UK is particularly strong in turbine-engine and civil/military aircraft manufacture and biomedicine; and these are the typical industrial sectors that rely on many advanced materials with high value added through quantitative control of their chemistry and manufacture process by novel solidification technologies.