Is it a metal, is it a glass?
Out here in the thicket of minor metals applications, procreating like so many iodic crystals on a hafnium wire, here is one of the latest – metallic glass.
Yes, you read that right. Neither purely metal nor purely glass, this new material – which has been trademarked Liquidmetal – can be cast like a metal but has some of the properties of glass.
It has been described to me like this – in a conventional alloy you usually want crystals to form. In an amorphous alloy (an alloy without crystals) you are mixing a series of elements whose main purpose is to prevent this outcome. This is done by placing in conjunction elements of differing atomic size, as if they are different sized balls in a children’s ball pool, so it is impossible to stop the atoms from moving about. Meanwhile, the differential between the balls (atomic size) should be not less than 12%.
If you are into tennis, or happen to have a penchant for mobile phones with starting prices of £9,500 ($13,700) you might have already tripped over the alloy in a racket-head or in the shiny metal casing of a Vertu smartphone.
I came across Liquidmetal about 15 years ago, on a stand at the Farnborough Air Show. On display were two upright, parallel thick glass tubes. Pressing a button released a ball simultaneously at the top of each of them. One was a steel ball, which bounced a few times and then settled. The other was a ball made of Liquidmetal, which continued bouncing for much longer. This was clearly an alloy looking for a use. But what would that be?
The Liquidmetal series of amorphous alloys, designated Vitreloy, spun out from Caltech – the Californian equivalent of the Massachusetts Institute of Technology (MIT), have in the past decade evolved through several generations of chemistry and contain about 40-60% zirconium.
Is this the future for zirconium?
As alloys go, zirconium as a base for other elemental additions is unusual. As an element, it falls into the basket of those that minor metals people handle on the basis that it is relatively rare in its metal form and difficult to deal in. It is classified as “dual use”, and subject to regulatory control under the Treaty on the Non-Proliferation of Nuclear Weapons, because it is used in the nuclear industry for tubes to house uranium granules in fuel assemblies.
Its production is dominated by state-owned or state-dependent organisations whose main purpose is nuclear, which means they are not well adapted to serve the non-nuclear sector. It is the job of minor metals folk to navigate through this and, ideally, deliver furnace-ready goods to those who need them.
Following the Fukushima accident in 2011, this became a bit harder for zirconium, because its output dropped as the construction of new nuclear power stations hit the buffers. Today, we estimate total zirconium output of about 4,500 tonnes worldwide (down from about 6,500 tonnes in 2011), out of which about 10% is suitable for Vitreloy.
I cannot claim any special insight that led to my involvement with zirconium – it was just one of a series of elements that first moved from east to west in the early 1990s following the collapse of the Soviet Union. It was a period that needed merchants to be open-minded enough to handle stuff they didn’t know much about – and we were hungry enough to do the learning.
As regards the make-up of the alloy itself, early formulations included zirconium 41.2% and beryllium 22.5%, but environmental rules restricting the use of potentially toxic beryllium meant this element was replaced. A more recent Vitreloy (106a) is now zirconium 58.5% with copper 15.6% and nickel 12.8%, among others.
Finding its niche
While Liquidmetal was licensed to manufacturers which thought they might be able to harness its amazing properties, it was one of those inventions that, although quirky and interesting, never quite found its revolutionary niche. Even if it was enough to get this old metal merchant interested, it was not about to change the world, was it?
That was until now. The revelation on March 8 that the US Patent Office had granted Apple the exclusive right to use the alloy for the home button on iPhones and iPads rather changed things.
Out here in the minor metals thicket, we had had an inkling that something was happening because of a trickle of zirconium enquiries from as far afield as Japan, Germany, the USA, and France, all asking for peculiar quantities and specifications. In minor metals, this was not bush wire but a clarion call. When these enquiries turned to orders, it was becoming clear this alloy had become a commercial reality.
We can’t be sure – and perhaps Apple hasn’t finally decided this either – but the thought that the iPhone home button will move to Vitreloy shows us how alloy development and material science lies behind objects we have wrongly almost taken for granted. Who would have thought, for example, that the SIM card liberation tool that comes with the iPhone (and is usually placed safely in a bottom drawer) is already made from it?
Aside from the iPhone, an array of applications for other purposes lies on the horizon – medical companies are looking at prosthetics (bouncy hip joints for the elderly should be fun), watchmakers are looking at precision parts, and Nasa is looking to use Vitreloy to collect solar wind. All now have the opportunity to harness an alloy with low shrinkage rate (0.5%) on casting, almost no post-treatment, high strength and corrosion resistance, high elastic limit, and lack of grain boundaries; a material combining some of the best qualities of steel, glass and plastic all in one.
It would appear to be the perfect cocktail of functionality and cost saving – the very essence of a major modern minor metal application.
Published May 11th 2016 on www.metalbulletin.com