Monocrystalline copper alloy features unprecedented elasticity

mechanics

Editor of the Technological Innovation Website – 11/29/2022

Monocrystalline copper alloy features in elasticity

Sample of the copper-based monocrystalline alloy developed by the team.
[Imagem: Sheng Xu et al. – 10.1038/s41467-022-32930-9]

monocrystalline alloy

Single crystals, or single crystals, are essential for materials research because their purity and homogeneity facilitate the study of phenomena such as superconductivity, magnetism, semiconductivity and others, mainly in the field of quantum technologies.

Single crystals are materials in which the crystalline network formed by its atoms is continuous and uninterrupted, with the atoms occupying regular positions, which are repeated indefinitely in space – in comparison, polycrystals are composed of many crystallites of varying size and orientation, with the “boundaries ” between them representing discontinuities, which typically result in loss of properties.

With the improvement of techniques for synthesizing single crystals, these materials have been drawing attention to applications on a macro scale, and it is now possible to synthesize single crystals of several centimeters.

Now, Sheng Xu and colleagues from the University of Tohoku, in Japan, have managed to synthesize single crystals of a copper alloy with the highest elastic tensile stress ever achieved so far for a material at room temperature.

The copper-based alloy exhibited an elastic tensile stress of >4.3% at room temperature – for comparison, plain steel has an elastic stress of

Monocrystalline copper alloy features in elasticity

The alloy properties, shown in the graph labeled “Our work”, are unmatched.
[Imagem: Sheng Xu et al. – 10.1038/s41467-022-32930-9]

elastic tension

Elastic stress, or yield strength, measures how much a material can be stretched and still return to its original shape before undergoing plastic deformation.

Theoretically, most metals and alloys can withstand a strain value of about 10%, but this is only true for their crystals at the micro or nano scale. When these metals are in their bulk form, as in most practical engineering applications, elastic strain typically falls below 1%.

Recently, the same team had synthesized a superelastic metallic alloy with elasticity similar to that of human bones. But now they worked with a much simpler material and of wider technological interest, an alloy of copper, aluminum and manganese (Cu-Al-Mn).

“Our raw alloy can be used as a material for springs with high recovery capacity, and can also be applied to devices that employ strain-mediated sensors, such as electronic stretchers,” said Xu. In any case, the low Young’s modulus of the new alloy also resembles that of human bones, which opens up the possibility that this new material will also be used in medical applications.

Another good news is that the material can be manufactured by a cyclic heat treatment technique, a simple method that allows to produce the superelastic alloy at a very low cost.

Monocrystalline copper alloy features in elasticity

Stress-strain curves of the new alloy obtained by charge-discharge tests at room temperature.
[Imagem: Sheng Xu et al. – 10.1038/s41467-022-32930-9]

hooke’s law

The elastic softening behavior presented by the new monocrystalline alloy meant that the relationship between tensile stress and deformation was not linear, that is, it does not follow the traditional behavior of Hooke’s law, the law that describes the deformation caused by the force exerted on it. a body.

Hooke’s law is actually a theory of elasticity, generalizing that the elasticity of an object is proportional to the tension applied to it. To obtain a large elastic deformation, high strength and a low Young’s modulus are required, the number that reveals how easily a material can stretch and deform. But in conventional metallic materials the relationship between these properties is a win-lose one.

Even so, the new material presented, in an unprecedented way, a low Young modulus (

In other words, the material is highly elastic, even when exposed to small amounts of stress, and is remarkably strong.

This immediately brought the alloy to the attention of the industry. The team announced that it is already partnering to perform functional fatigue tests of large elastic deformations in the alloy, something fundamental for its practical applications.

Bibliography:

Article: Non-Hookean large elastic deformation in bull crystalline metals
Authors: Sheng Xu, Takumi Odaira, Shunsuke Sato, Xiao Xu, Toshihiro Omori, Stefanus Harjo, Takuro Kawasaki, Hanus Seiner, Kristna Zoubkov, Yasukazu Murakami, Ryosuke Kainuma
Magazine: Nature Communications
DOI: 10.1038/s41467-022-32930-9

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