Looking ahead with light metals

Materials World magazine
,
24 Sep 2018

The Institute’s Light Metals Division board members Mike Clinch, Innoval Technology Ltd, and Paul Lyon, Luxfer MEL Technologies, UK, highlight some of the most exciting developments and opportunities in the UK light metals community.

The major industrial light metals – aluminium, magnesium and titanium – are currently all enjoying strong growth conditions in key market sectors, due to their excellent attributes that make them ideal materials for tackling many of the world’s grand challenges. This has resulted in resurgence activity across the technology readiness level scales in the UK, from the launch of major new research programmes, technology development centres and production capabilities, to the introduction of innovative new products to the market.

Aluminium

The most mature and widely available of the light metals, aluminium continues to see increased levels of demand around the world. According to World Aluminium statistics, the global production output in 2017 was of the order of 60 million tonnes, an increase of around 50% over output levels at the beginning of the new millennium. Demand continues to increase at around 4–5% compound annual growth rate, with some regions and market sectors having enjoyed considerably higher rates in the last decade.

Aluminium is an ideal here-and-now solution for lightweighting programmes, due to worldwide concerns over increasing urbanisation and air quality driving a need for cleaner, more sustainable transportation. As a result, aluminium is seeing rapid deployment and unprecedented growth in the passenger vehicle sector. Much of the technology now being implemented was developed in the UK as a result of the pioneering work undertaken in collaboration between Alcan and Ford throughout the 1980s and 1990s. At that time, Ford had ownership of what is now Jaguar Land Rover, which today uses aluminium structures across all of its vehicle platforms.

The UK will continue to play a major role in this field, as highlighted by the recent opening of the new Constellium R&D Centre and Advanced Metal Processing Centre (AMPC) at Brunel University London, UK. This is a major expansion of Constellium’s existing University Technology Centre on the campus, allowing the company to transition technology from laboratory scale to its production facilities around the world. New, dedicated equipment has been commissioned to form, join and test prototype automotive components such as crash management systems, body structure components, and battery enclosures for electric and hybrid vehicles, from state-of-the-art facilities on the Brunel campus.

In the past, lightweighting and electrification have been viewed as alternative or even competing ways to achieve low-emission targets. However, the dramatic shift towards hybrid and battery-powered electric vehicles (EVs) by almost all major automotive manufacturers is creating an increased demand for aluminium, since lightweight architecture is essential to counter the significant additional on-board mass of the battery pack – according to US Environmental Protection Agency certification, the 75kWh battery on the Tesla Model S weighs 530kg – while retaining acceptable environmental performance, driving experience and range for the consumer. This is creating increased demand for aluminium extrusions, which are starting to be incorporated into battery box components.

At the moment, a typical saloon car with a conventional internal combustion engine contains just under 20kg of aluminium extrusions, whereas the equivalent for an EV would contain around 65kg. In a 2017 report by Ducker Worldwide, it was estimated that the aluminium content could increase to over 250kg per vehicle – 16% of total average kerb weight – by 2028. Earlier this year, market analyst CRU Group reported that by 2030 aluminium demand from EVs alone would approach 10 million tonnes, a ten-fold increase from 2017. All analysts agree that aluminium automotive usage from castings, extrusions and rolled products will be significantly higher than we see in internal combustion engine vehicles today.   

Another major focus area for the aluminium industry is the transition towards cleaner primary metal production, utilising low-carbon energy sources in parallel with more widespread adoption of secondary metal supply options as both availability and quality increase. By the year 2023, it is projected that the annual global production capacity of secondary aluminium will have reached 40 million tonnes – greater than the size of the entire aluminium industry in the year 2000. Producers like Hydro, Norway, are promoting the benefits of products such as Hydro 4.0 – 4.0kg of CO2 per kg of aluminium – and Hydro 75R – with a minimum of 75% recycled content.

Closer to home, partners in the Innovate UK reality project – Jaguar Land Rover, University of Warwick, Axion Recycling, Brunel University, Innoval Technology, Norton Aluminium, and Novelis – have demonstrated the feasibility of producing metal from 100% recycled content, at just 0.5kg of CO2 per kg of aluminium, while still achieving target levels of performance.

Magnesium

Magnesium is, or has been, used in a wide range of applications, ranging from a consumable in the desulphurisation of steels to components in general automotive, Formula 1, aerospace sectors and even as a containment vessel in Magnox nuclear reactors.

Global production of magnesium has grown year on year since 1994, and current supply has exceeded one million tonnes per annum, according to IMA–CM Group. A major factor that has allowed such wide applications is the innovation to develop processing technologies and suitable alloys to match the customer needs.

The aerospace and high-performance motorsport communities have long recognised the benefits of high-performance magnesium alloys for providing competitive advantage through low weight and high strength-to-weight ratio. Magnesium’s weight advantage over aluminium, of which the latter is 50% heavier, makes it an attractive alternative, especially now that higher fuel costs and increasingly stringent environmental requirements are driving aerospace initiatives to reduce weight and carbon dioxide emissions. Aerospace manufacturers such as Boeing, Rolls-Royce, Airbus and Leonardo have all used magnesium alloys to reduce weight in aero engine frames and components, helicopter transmissions and aircraft wheels.

For oil and gas

While latest generation aerospace and automotive alloys are designed to be robust and offer service for many years, there are other opportunities where magnesium can be designed to do its job, then disappear.

In recent times, the oil and gas industry has shown a significant move away from vertical drilling into reservoirs of oil and gas, towards extracting these resources from shale rocks. This involves drilling long lateral wells and using fluids and hydraulic pressure to fracture the rocks and release the precious petroleum products. These lateral wells, of up to 6,000m in length, are then plugged to section the wells into many stages where the shale rocks can then be individually fractured. After the rock fracturing process, the plugs – ball activated sleeve valves or bridge plugs – used in this step are typically removed by milling/drilling, using drilling motors on a long length of flexible coiled tubing. This is a costly process requiring equipment on site, capable of drilling for thousands of metres.

Controlling magnesium’s electrochemical activity to its advantage, Luxfer MEL Technologies (LMT) – formerly Magnesium Elektron – has developed a range of SoluMag magnesium alloys designed to rapidly degrade in fracturing fluid, while also having excellent tensile and compressive strengths. Downhole tools and components made from SoluMag degrade after the hydraulic fracturing step, eliminating the need for the costly drill-out of the plug in a completed well.

The healthcare sector

The number of deaths due to cardiovascular diseases increased by 41% between 1990 and 2013, climbing from 12.3 million deaths globally to 17.3 million, according to the New England Journal of Medicine, 2015. The minimally invasive procedure that’s had the largest impact on cardiovascular disease is arguably percutaneous coronary intervention (PCI), commonly known as coronary angioplasty. This procedure is used to treat stenotic – narrowed – areas of the coronary arteries caused by the accumulation of fatty materials such as cholesterol and triglycerides resulting from atherosclerosis. PCI involves the insertion of a medical device manufactured using biomaterials, known as a coronary stent, into the coronary artery. These stents have made a significant contribution to improving the outcomes of patients suffering from the issues associated with long-term chronic conditions.

Despite these real and positive benefits, permanent stents risk causing the immune system to react, potentially leading to late stent thrombosis, or strut fracture-induced restenosis and coronary vasomotion. Biomedical technology company Biotronik, Germany, has identified an entirely new category of metallic cardiovascular stent, known as a scaffold, which would resorb over time.

Magnesium was selected for use, which is present and an essential mineral within the human body. Luxfer MEL Technologies – Magnesium Elektron – was formerly approached to develop a suitable magnesium alloy for the Biotronik scaffold designs. The two companies entered into a joint R&D programme in 2006 aimed at developing a bioresorbable magnesium coronary scaffold. The ten-year research programme has resulted in LMT’s SynerMag magnesium alloy system being used as the platform material in the Biotronik magnesium scaffold, the world’s first clinically proven magnesium-based bioresorbable scaffold, called Magmaris.

The SynerMag alloy had some unique material challenges to overcome to allow delivery and subsequent expansion within the artery while also achieving the strength to support the radial forces of the artery – all this for a product that has a structural strut thickness of only 150 micrometres. Finally, and importantly, a fast resorbtion time of approximately 12 months is achieved after implantation.

Titanium

Titanium is the fastest growing metal in the aerospace manufacturing sector. But, with relatively poor buy-to-fly ratios for safety critical structural and engine components, the majority of titanium-forged billets are machined to swarf – turnings and chips – as waste. Over the last few years, the University of Sheffield’s Ben Thomas and Martin Jackson have developed a continuous process to consolidate such waste material into wire for a range of potential applications.

In the next 15–20 years the amount of air travel will double and outpace GDP growth. With rapid growth in air travel, particularly in Asia-Pacific, new aircraft models are being designed and built at a frantic pace. The major growth is in fuel-efficient, single-aisle aircraft such as Boeing 737 and Airbus A320. Due to the increasing use of titanium in new aircraft, titanium usage is also increasing faster than any other metal. Titanium is used for fasteners and high-strength forgings to support the composite fuselage and wing structures in wide body aircraft, such as Boeing 787 Dreamliner and Airbus A350-XWB.

Titanium has excellent galvanic corrosion compatibility with carbon fibre composites due to carbon and titanium being cathodic in nature, as opposed to the commodity metals such as steel and aluminium, which are anodic. Titanium also has a similar thermal expansion coefficient to carbon, which helps to reduce residual stress issues during joining, manufacture and in service performance. In addition, titanium is intensively used in landing gear as high strength titanium forgings and springs.

It’s not just commercial aircraft – titanium is extensively used in military aircraft. For example, an F-22 Raptor has up to 40% of titanium in weight with the majority of the forging ending up as waste in the form of machined swarf.

Work within the Sheffield Titanium Alloy Research group has manipulated the Conform tooling – an extrusion process that uses a single revolving wheel as the driving force – designs and running parameters to consolidate titanium particulate into wire. The Sheffield group has also successfully extruded development titanium alloy powder and titanium-machining swarf. All these feedstocks have been successfully consolidated into wire, rod and thin strip forms with diameters ranging from 5–10mm, but larger diameters are possible with larger machine types.

If this technology can be developed further and commercialised, then low-cost titanium alloy wire for valve and suspension springs, additive manufacturing feedstock and welding wire could be a reality.

Looking ahead

There is some exciting work taking place within the light metals community, from fundamental R&D through to commercial-scale activities. In parallel, the Light Metals Division (LMD) has recognised a need for the UK to be training and developing more materials scientists, engineers and metallurgists to continue the strong tradition of innovation in light metals and to become the next generation of industry leaders.

It is going about tackling this in a number of ways, firstly by engaging with the Bloodhound SSC Education team – the largest STEM programme in the UK – to raise awareness of materials as a subject and explain the importance of using light metals within the Bloodhound vehicle design. Secondly, LMD’s academic board members regularly share ideas and best practices for undergraduate and postgraduate teaching. Some of the best examples of this are to be found in Centres for Doctoral Training (CDT), shared between multiple universities. It is very much hoped that these will continue to prosper within the next phase of CDT funding, while continuously evolving to embrace new disciplines, for instance, advanced modelling and digitalisations.

Finally, new large-scale research centres such as the Brunel AMPC and the new LightForm programme – a five-year multidisciplinary project led by the University of Manchester, with partners at the University of Cambridge and Imperial College London, UK – will provide a critical mass of industrially relevant projects and a pipeline of talent for the future.

The vision is to provide the enabling science that will allow UK industry to achieve a step-change in the performance of the next generation of wrought, light-alloy, formed components, and to innovate in the move to a circular economy and digital simulation in manufacturing.