We have a formula for creating supermaterials bordering on the principles of magic: high-entropy alloys.

Elinvar is a unicorn, a new material that seemed impossible, created by man using principles bordering on magic, those that allow high entropy alloys to exist.

Elinvar has an exceptional property that any textbook will throw to the ground: it is a metal that, when heated, increases its rigidity. Where are we going to use it? It cannot even be produced on a large scale. This is just one example of a new era that is being forged in the leading laboratories and research centers of the world: the era of high-entropy alloys.

The Defense Advanced Research Projects Agency (DARPA) and the US Air Force Research Laboratory (AFRI) have invested heavily in their study. your report Finding Ways to Realize the Revolutionary Potential of a High Entropy Alloy the best laboratories, universities and specialized researchers in the USA participated in it. It is quite possible that whoever controls the incoming materials will dominate the world, as has happened throughout the history of mankind.

Political power that copper meant

8000 BC e. a man, driven by curiosity, took a piece of native copper that he found while walking in the countryside, and after striking it, found that it deformed, hardened, and could also take on various forms. Mankind lived in the Neolithic era, and many tools made of stone or wood were replaced by copper ones. These were not only tools, but also very effective copper weapons. The peoples who knew this secret dominated the world. The Copper Age, the Eneolithic period, began.

Several thousand years later, around 5000 BC, somewhere near present-day Turkey, perhaps inspired by dreams of fires at dusk, other people discovered that sands with certain characteristics (malachite and azurite) could be mined the amount of liquid copper, and that copper can be cast into complex shapes.

The earth is a storehouse of metals

Man discovered that the Earth is a storehouse of metals, from which, knowing how, materials with magical properties can be extracted.

Coppersmiths needed another 2000 years, around 3000 BC. and not far from this part of the world, to discover that the addition of a small amount of tin makes the resulting material harder and more resistant. Thus was born a revolutionary formula: an alloy where the sum is much better than the individual parts, and with it the Bronze Age.

Throughout history, the world has been dominated by those who knew the secrets of materials, and for this reason we named historical periods after the material that allowed us to make tools and weapons more powerful than those of our enemies: stone, copper, bronze, iron … silicon, carbon ?

Technological limitations have stopped the miracle of alloys

The possibilities for making alloys seemed limitless, but there is a limit to the properties that can be achieved in one metal with the addition of others. From certain amounts of added components, the resulting alloy instead of improvebegins to show negative properties, such as fragility.

From then until today, metallurgists have known that there is a limit to the amount and percentage of alloys that can be used.

In the late 19th century, Sir Henry Clifton Sorby developed a microscope that made it possible to observe the microstructure of metals, revealing the microstructure of steel. Then we learned that the loss of properties was associated with the appearance phases complex (intermetallic compounds), usually brittle, that appeared in this microstructure, and that this happened when certain proportions of alloying elements were reached.

Thus, we realized that the limit was in one or two simple phases (commonly called cubic because the atoms are organized in cubes) in order for the properties of the alloy to be optimal.

Four rules that set limits

In 1938, metallurgical chemist William Hume-Rothery identified some rules (the four Hume-Rothery rules) that explained why this happened. If these rules are not followed between two alloying elements, a single phase will not form where the atoms of the two occupy the positions of those cubes, and hence other, more complex phases are generated that will degrade the material.

These four rules are related to the basic aspects of the properties of atoms (size, electronegativity, valency, tendency to organize or break down into cubes of the same size and configuration) and have governed alloys for over 5,000 years.

high entropy

But in 2004 everything changed. Two research teams led by Brian Cantor and Jian-Wei Ye (at the same time and in different places, which is very common for great scientific milestones) discovered and demonstrated that if the entropy of the mixture is high enough, above a given value, alloys can get one simple phase, in which the atoms fuzzy occupy different places of the cube.

Entropy measures the greater or lesser disorder of the molecules of any material. Given this confusion and thousands of years later, Kantor and Yeh went beyond by showing that alloys of many components of a single phase can form without observing the Hume-Rothery rules, increasing the possible viable alloys in unlimited quantities. path. This is how the concept was born and became the source of high entropy alloys.

Initially, only mixtures were considered in which all components are in the same proportion, but the concept quickly spread to mixtures of many metals, but not necessarily equiatomic ones (with a balance in the number of atoms).

This revolution in the world of metals was especially evident when evaluating the properties of high-entropy alloys. The resulting materials can compete with the most well-known alloys in areas such as high temperature, magnetic properties, hydrogen storage, etc.

In just 18 years, he has gone from the first two publications of Kantor and Yeh to more than 5,000 related publications in the last year.

We are faced with a discovery similar to that of bronze or steel. The materials we have today are at the limit in all current technological applications, and small improvements could allow these technologies to take a giant leap. High entropy alloys promise such improvements.

Properties that we hope will improve the world

The combinations of elements to create high-entropy alloys are almost limitless, but despite new modeling techniques, the lag between discovery and development and the ability to use a new material for a new specific application can be many years, especially in fields such as biosanitary or aerospace.

In many possible combinations of elements, there are so-called critical metals, which are difficult to obtain, expensive and harmful to health if mishandled. Finding alternatives is also a problem in materials science.

Multi-component alloys can also be an outlet for the recycling of hard-to-separate metals in the electronics industry. There are already works showing that it is possible to develop high-entropy alloys starting from alloys products already made for other purposes, in the development of which we took part from IMDEA materials.

Are we at the beginning of a new era of humanity, the Age of High Entropy Alloys? Centuries will pass before there is a perspective that allows us to assert this, but let’s not deny that it looks good.

José Manuel Torralba, Professor at Carlos III University of Madrid, IMDEA MATERIALS

This article was originally published on The Conversation. Read the original.

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