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What Is a Eutectic?

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  • Written By: Mary McMahon
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  • Last Modified Date: 04 November 2014
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Eutectic is a word which is used in reference to a mixture which contains two or more components in proportions which allow them to solidify at the same temperature. The point at which the components start to solidify is known as the eutectic point. Eutectics have a number of applications, most particularly in the field of metalworking, where they are popular in the form of alloys used for things such as soldering and casting.

It is not always possible to achieve a eutectic mixture. It is necessary to adjust the ratio of components in the mixture and to closely control the components for impurities which could imbalance the mixture and throw off the solidification point. In the case of a metal alloy, the components start out as heated liquids, and during the cooling of the liquid, the components start to crystallize and solidify at the same time as they reach the eutectic point.

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The structure of a eutectic mixture tends to be lamellar in nature, with the materials layering over each other as they crystallize out of the liquid mixture and start to solidify. This can contribute to the strength of the cooled solid, as the layers of material are less likely to crack and separate. The simultaneous crystallization also ensures that the distribution of components in the mixture is highly even in nature, which can also be beneficial to strength. It is possible to see the structure of the mixture with the assistance of a microscope, and microscopy can also be used to determine whether or not the mixture of components is even.

There are numerous examples of eutectic mixtures beyond metal alloys. Salt and ice, for example, can form a eutectic mixture, as can many chemical compounds used in the pharmaceutical industry. Eutectic mixtures also play a role in cooking and food preparation, as anyone who has had a baking recipe go disastrously wrong is probably well aware. In all of these cases, the properties of the eutectic mixture play an important role in the properties of the finished solid component.

Information about well known eutectics and their eutectic points are readily available on the Internet and in industry reference materials. Information about metal alloys in particular is very widely distributed, as many people work with alloys and need to have information about their properties to make decisions about when and where to use specific alloys. Packaged alloy products also usually contain a brief overview of their properties, as seen with solders.

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anon212361
Post 4

I am a pharmacist and we have a lot of applications of eutectic mixtures which allow us to formulate some products without the need to use organic solvents which are considered as hazards toxic substances to the environment.

So, eutectic could be called green mixtures or environment friendly.

Charred
Post 3

I am amazed at some of the metal adhesives that I see advertised on television which apparently bond so tightly that you can hang weights on them.

I don’t how they work; I guess there is something similar going on, where the properties of the metal and the target substance are kind of combining and bonding at a certain temperature. It’s almost like super glue for metal.

MrMoody
Post 2

@SkyWhisperer - I don’t know much about soldering, but I do know something about salt and ice, mentioned in the article.

We have some big snowstorms where we live, and we need salt thrown on the ground to prevent it from freezing. The problem is that there isn’t always enough salt.

This past winter was so bad we had to import salt from the neighboring state, and of course that took awhile. Still, it was good that it finally got done, and it’s useful to know a little bit about the science behind it.

SkyWhisperer
Post 1

I used to use a soldering iron a long time ago, back when I dabbled in electronics. I remember when I used it that the solder had a very small window within which it would melt and then solidify on the connection.

From what I’ve read in the article, I guess the solder contained eutectic mixtures, although I don’t recall the metals, whether it was tin or whatever. All I knew was that it melted and solidified very quickly, and on some occasions if I wasn’t careful I would burn a component.

Soldering is part science, part art. This was before I moved on to using solder less breadboards and later, printed circuit boards that removed the soldering process out of the equation.

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