Published 20th June, 2019 by Nadine Bloxsome

Continuing its leadership in the growing market for specialised high-performance alloys, Rio Tinto launches Revolution-Al™, a new aluminium alloy developed to make lighter car wheels.

Rio Tinto Aluminium chief executive Alf Barrios said “As we partner with customers we’re seeing an increasing demand for specialised alloys and other products to meet their specific needs. Developing these products is at the heart of our business, from research and development, to offering technical expertise and marketing as well as collaborating with OEMs.”

Rio Tinto vice president of Sales and Marketing Tolga Egrilmezer said “Revolution-Al™ is a clear example of how we aim to be the partner of choice, in order to deliver responsible solutions to our customers and the whole manufacturing ecosystem. Our new wheel alloy is stronger, allowing designers to make a lighter wheel, which in turn can make cars safer and more appealing to end consumers, in addition to having reduced CO2 emissions.”

• Rio Tinto’s Revolution-Al™, the latest addition to Rio Tinto’s High Strength 3xx Series Alloys, is a new aluminium alloy for automotive wheel weight reduction. Among its benefits: - Wheel design improvement provides opportunities to improve visual appearance, tire performance, vehicle handling and manoeuvrability as well as reduce CO2 emissions and tire wear; - Lighter wheel with a 7% weight reduction versus its standard design—resulting in improved fuel efficiency and reduced CO2 emissions; - 15 to 20% stronger than traditional wheel alloy A356.2 (which allows the wheel weight reduction); and - Easy and cost-efficient manufacturing solution: - Seamless transition with existing casting processes—allowing manufacturers to use their existing tooling; - 2-hour shorter ageing cycle (heat treatment) compared to A356.2—potential for increase in productivity; and - No exotic elements for recyclability—no impact on end-life automotive recycling.

• Rio Tinto’s objectives for the development of Revolution-Al™ were to: - Improve mechanical properties by improving chemical composition of current aluminium alloys (i.e. control inherent detrimental phases in the alloys); - Lower wheel weight by improving mechanical properties; - Avoid foundry operational changes (i.e., no need for additional investments); and - Ensure transparent implementation for castability and recyclability.

• A356.2 (good mechanical properties, widest application is cast aluminium wheels) and 357.1 (used for higher strength applications, ex. suspension parts and aerospace) are the most commonly used aluminium alloys in the foundry industry. They provide medium- to high-strength properties with excellent fluidity and corrosion resistance.

• Revolution-Al™ is Rio Tinto’s new patented alloy that improves on A356.2 and even 357.1. Specific alloying additions were made to eliminate the β and π phase formation and, as a result, improve the strength/ductility ratio. o ex. 357.1: Due to higher magnesium content, (Pi) phase forms during solidification and thus absorbs a portion of the magnesium, which becomes unavailable for the precipitation of Mg2Si. In order to further improve strength/ductility ratio, manganese additions were made to modify the iron phase in 357.1. Manganese is well known for its iron phase conversion from β to α.

• Industrial trials of the new alloy, coupled with an official OEM test program, were performed using an optimised automotive wheel design. Most notably, due to inherent higher mechanical properties, a 7% weight reduction was obtained compared to the reference wheel design.

• Revolution-Al™ passed all OEM trials. Thirteen-degree (to simulate the behaviour of a car sliding sideways into a curb) and ninety-degree impact (to simulate a pothole impact) as well as rotary/cornering fatigue testing (to simulate wheels turning) requirements were successfully met.

• Our new alloy could also be applicable to other market segments (ex. chassis parts such as suspension or braking parts, tools).

• In terms of recyclability, Revolution-Al™ can be recycled onto itself. This means that customers can recycle their scrap instead of selling it at a discount, which is important concerning the cost of a foundry.

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