The most ductile metal is gold

Gold is the most popular metal in history, in culture, in the economy. For the possession of it, rivers of blood were spilled, family conflicts broke out, and even wars were waged. Its significance for the entire human civilization is based on its unique chemical and physical properties, on the features of the internal structure.

Gold is the most ductile metal. This quality makes it in demand everywhere: from jewelry to microelectronics.

The most "metallic" metal

In gold all the most obvious properties that scientists call metal are concentrated. By electrical conductivity, it is second only to silver, copper and pure palladium. By thermal conductivity - the same silver, copper and cobalt. According to the ability to absorb thermal energy, gold is second only to exotic bismuth, ahead of mercury and silver. According to other "metallic" properties - malleability and reflection of light - it is the champion. Gold is the most plastic metal in the world, and its brilliance is legendary.

The molecular structure of gold is also very "metallic." It is a geometrically correct crystal lattice with positive ions in the nodes and a cloud of "electronic" gas dense in concentration between them. This part of the atom is made up of free electrons located on the external energy level. They create a force of attraction between the grid nodes, which ensures the ability of the metal to deform without disturbing the overall integrity. So the most ductile metal is arranged.

Determination of plasticity

From the Greek Πλαστική ("sculpting", "modeling") there was a word "plastic", which gave the root to others, connected with the change in the shape of a solid body. Plasticity is a property of a solid body to change its shape and dimensions and to preserve residual deformation after the termination of the action of external forces without changing the volume and breaking integrity.

For metals, this is one of the most important characteristics that makes it possible to use them in practice. Without the possibility to impart the desired form to the metal preforms, it would be impossible to create even the simplest household items. Gold is the most ductile metal, and articles made of it are an example of what form can be given to a sufficiently compliant material by forging, pressure, rolling, drawing, drawing, etc. The reverse property of the material is brittleness.

The plasticity test

The ductility characteristics of metals are usually determined in static tests. The most indicative is the tensile test. To find out which metal is the most plastic, it is necessary to subject to such an effect samples of the same size under similar temperature conditions. The amount of deformation that a metal sample can withstand destruction is an objective index of plasticity.

The numerical expression of the result of tensile tests is the two main coefficients. Relative elongation is the percentage of the increased length of the sample after the rupture caused by the deformation, to the original one. The most plastic metal - gold - has a rate of 65%. For comparison: for iron - 40-50, for aluminum - 30-40.

The second index of plasticity is the relative narrowing of the cross section of the sample. In gold, the original cross-section of the sample is 90% larger than what it has before the break. In aluminum, this figure is 80%, for copper - 75%.

Soft, viscous and durable

On the scale of Mohs hardness in gold, the figure is 2.5-3.7. In pure form, this metal is much softer than many widely used materials and is scratched with a knife or even a fingernail. Therefore, to avoid rapid wear of gold products, special hardening ligature elements, usually silver or copper, are added to the metal for their manufacture. There are also harmful impurities in gold. The most ductile metal in the Mendeleev table in the presence of lead, platinum, cadmium or sulfur becomes brittle.

The softness of gold is of a special nature, it is supplemented by its viscosity and ductility. The convenience of molding and technological processing of parts is supplemented by high tensile strengths of 3300 kg / cm ² . Such a unique combination of physical and mechanical characteristics of gold has been used since ancient times. An example is gold leaf.

Domes in Russia are covered with pure gold ...

Despite the long history of gold mining, this metal has always been rare and precious. This is the most ductile metal. This quality makes the use of gold foil for decorative decoration of interior elements or even to cover church domes with cost-effective. To cover a large area, very little precious metal is required: 1 gram of the plate can be uncoated into a 1 m ² sheet.

Even a manual method of producing sheets for gilding makes it possible to achieve a thickness of a thousandth of a millimeter. This thickness allows gold plates to stick to the surface due to molecular attraction. The technology of obtaining a sushi has been significantly improved. Now, robotic lines are used to flatten gold plates, but the process is based on high plasticity of the starting material.

Golden thread

The ability of gold to withstand a tensile stress without a rupture is known from the very beginning of its commercial use. The manufacture of such a wire for jewelry was established in ancient times - the ancient masters already knew which metal is the most plastic. In the middle of the XX century, a microwire with a gold core was made, which even with plastic insulation was 7 times thinner than a human hair. From 1 gram of metal, a continuous gold thread about 3.5 km long was pulled.

Today's technology has brought the thickness of the gold wire to several microns, further development of the technological advantages of metal continues.