Making a new nickel
The cost of manufacturing coins now outstrips their actual value. Can developing new alloys change this? Khai Trung Le talks to Eric Lass on his recent work redesigning the US nickel.
Physical money faces the dual threats of escalating production costs and widespread societal acceptance of digital alternatives. The ubiquitous US5¢ coin, known as the nickel, faces competition as its namesake element has found increasing use in modern products, which led to a subsequent rise in prices. The nickel currently comprises around 75% copper and 25% nickel. However, the production cost of the nickel has outstretched its actual monetary value – fluctuating around 7¢ for each coin – for years. The US Mint began exploring alternatives in 2010, and inviting organisations to support in 2013, including the National Institute of Standards and Technology (NIST), USA, which has developed three low-cost and seamless replacement alloys that reduce the raw material cost of current USA coinage.
Numerous restrictions were imposed. Eric Lass, Materials Research Engineer at NIST, told Materials World that not only do replacement alloys have to be compatible with the production facilities in Philadelphia and Denver, but the new alloys need the same properties as current nickels. ‘This includes electromagnetic conductivity, resistance to wear and corrosion, and especially colour,’ he said.
Colour would be one of the defining problems of the project, which proved hard to assess but also impossible to ignore. ‘Colour in coinage hasn’t been comprehensively studied, but it was something we had to be very specific about – not only did the nickel have to be the same colour fresh from the slow-cooling process, but it had to remain so years afterwards.’
Worth the hassle
Of the three replacement alloys, Lass noted that a copper-nickel-zinc composition that stayed true to the nickel’s current properties would be around 25% cheaper to manufacture. The NIST also found alloys that would result in reductions as high as 40–45%, should the US Mint remove restrictions on the physical parameters.
‘The electro-conductivity has to be the same. As long as we’re still using coins in a vending machine, or electronic coin counting machines, it could cost anything between US$1–10 billion to reprogram the devices,’ Lass said. ‘However, if we removed restrictions in weight, it would open the door for something like an aluminium alloy. It’s the same with colour – the US Mint could slowly phase in a cheaper material, gradually changing it. In 20 years time, the nickel would have a slight yellow tint, but by then, no one would care.’
Lass was sympathetic to resistance from the US Mint, which principally argued whether the American public would trust a nickel that has so far not changed in 152 years. ‘Me knowing the material, and knowing it will work the same way is no big deal. But, seeing a nickel that was always silver now yellow is a little strange. People fear change, maybe Americans more so than anybody.’
Down to the genome
The NIST team based their project on an integrated computational materials engineering (ICME) framework that uses a large quantity of computer modelling to explore how the different components would react when mixed together. Lass stated that the use of the ICME framework enabled the team to conclude their work within a year. ‘We were able to put together a framework for designing an alloy, identifying and using our model to get the correct alloy and then move forward with making the prototype.’ The team’s work can be read in the paper, Systems Design Approach to Low-Cost Coinage Materials, published in Integrating Materials and Manufacturing Innovation.
The ICME framework is parented by the Materials Genome Initiative, an Obama-era project started in 2011, and supported by NIST. Lass continued, ‘This is one of the first real success stories that we had with using the ICME process – we identified three different alloys for application for the US Mint, and then provided compositions that are very close, if not identical to what they’ll be using. Whereas 10–15 years ago, it could have taken five years or more. I’d like to sell this as a success story in how we as materials engineers are evolving with technology, and it will only get better and better.’
Results from the project are unlikely to be compatible with other coins, specifically the 1¢. Lass said, ‘The cost of making the 1¢ coin is always going to stay at 1.5 times its actual value.’
You can read Systems Design Approach to Low-Cost Coinage Materials at bit.ly/2J7jwp0