NON-FERROUS ALLOYS: STRUCTURE, PROPERTIES, USES, EXAMPLES - CHEMISTRY - 2024

The nonferrous alloys are those that do not have in their composition iron metal. Therefore, it does not consist of any of the types of steels, and its main base can be that of any other metallic element; such as aluminum, silver, copper, beryllium, magnesium, titanium, etc.

Unlike dense steels, ideal for the metallic support of buildings and bridge cables, ferrous alloys are usually lighter and more resistant to corrosion. From here to that the number of its applications increases exponentially, each one demanding a specific type of alloy, with an exact metallic composition.

Bronze sculpture - an example of a non-ferrous alloy. Source: Pixabay.

Some of the oldest and most well-known non-ferrous alloys in history are bronze and brass. Both have copper as a metallic base, with the difference that in bronze it is predominantly mixed with tin, and in brass with zinc. Depending on their combinations and composition, bronzes and brasses with extensive properties can emerge.

And moving into the modern present, the alloys that make up electronic devices are essentially non-ferrous. Also, the frame of the most sophisticated vehicles and aircraft is made of these alloys, to give them strength at the lowest possible weight.

Structures of non-ferrous alloys

Each metal has its own crystalline structures, which can be hcp (compact hexagonal), ccp (compact cubic), bcc (body-centered cubic), or others.

When melted and welded into a solid solution that then crystallizes, the atoms of all metals join together through the metallic bond, and the resulting structures add or change.

Therefore, each alloy to a certain composition will have its own crystal structures. That is why to study them, one uses rather the terms of phases (usually denoted as α and β), represented graphically in a phase diagram as a function of variables such as temperature, pressure and composition.

From these phase diagrams it can be predicted at what temperature (liquid phase) the non-ferrous alloy of a system consisting of two or more metals will melt, as well as the nature of its solid phases.

Assume the silver-copper pair. By analyzing its phase diagram, physical and structural information can be extracted from the multiple alloys with different silver-copper combinations (10% Ag and 90% Cu, 25% Ag and 75% Cu, etc.). Obviously, metals must be soluble in each other so that they can crystallize into an alloy in a homogeneous way.

Properties

The properties of non-ferrous alloys are very diverse. For steels it is not very difficult to generalize, since they exhibit a synergy of the properties of iron with those of iron-carbon, Fe-C. Instead, the properties of non-ferrous alloys depend mostly on the metal base.

For example, if the alloys are aluminum or magnesium, both light metals, they are expected to be light. If titanium, a denser metal, is mixed with any other lightweight metal, the resulting alloy should be slightly lighter and more flexible.

If copper and gold are known to be good conductors of heat and electricity, then their alloys must offer materials that are cheaper, less soft, and more resistant to mechanical work and corrosion.

If all the properties and characteristics of this type of alloys could be generalized, they would have to be: less dense, mechanically more resistant in relation to their weight, more inert against oxidation caused by their environment, deformable, highly conductive of heat and electricity. For the rest, there are its many exceptions.

Applications

Aluminum

They are very light alloys, and therefore their structure should be bcc (the least compact). They can be deformed into multiple shapes, like cans, for storing food and beverages.

They tend to have high resistance to corrosion, but it is inversely proportional to their mechanical resistance, which increases when mixed with copper, magnesium or manganese. Those with better mechanical strengths find use as auto body parts, and for aircraft parts.

Titanium

-Titanium alloys find many applications for the design of bone prostheses and, in general, this metal is highly compatible with physiological matrices.

It is also used as parts of the frame and surface of aircraft, vehicles, motorcycles, golf clubs, among other artifacts and objects.

-Mixed with aluminum, its alloys have been used in the construction of the roofs of Japanese temples and pagodas, and in the statues of their dragons.

Silver

-Its alloy with graphite (Ag-C) has low electrical resistance and is therefore used as components of circuit breakers.

-Mixed with mercury, an amalgam with 50% Hg and a lower percentage of copper and tin is obtained, which is used to fill dental defects.

-Its alloy with copper gives it such resistance that it creates metal cutting discs and saws.

-In jewelery it is used in an alloy of palladium and platinum, resistant to scratches and the loss of its shine.

Magnesium

They are denser than aluminum, but otherwise their properties are similar. They resist atmospheric conditions well, so they have been used for the manufacture of automobile parts, in gearboxes, wheels, missiles, in short, in high-speed machinery (as well as in bicycles).

Beryllium

-Its Be-Cu alloy is used for electronic components for small devices, such as smartphones, iPads, wristwatches, tablets, etc.

-Ceramics (mixed with gallium, arsenic or indium), are used in electronic circuits with high current density.

-In medicine, beryllium alloys forge many of its instruments and devices, such as pacemakers, laser scalpels, scanners, the frame of nuclear magnetic resonance equipment, among others.

-It also forges part of the military and nuclear weapons, it has also made mirrors for satellites with beryllium alloys.

-Tools forged with these alloys do not produce sparks when subjected to high friction.

Examples

Some specific examples of non-ferrous alloys are:

-Monel and Constantán, both nickel-copper alloys, but with a composition of 2: 1 and 45% (55% copper), respectively.

-Cromel, whose composition is 90% nickel and 10% copper. It is used as part of the electrical system of industrial ovens, capable of withstanding high temperatures.

-Ti-6Al-4V, an alloy of titanium with vanadium, aluminum and other metals, especially used for biological purposes.

-Stelite, an alloy of cobalt and chromium.

-Magnalium, aluminum alloy with a low percentage of magnesium (less than or equal to 10%). They are practically aluminum sheets that are more resistant to traction and are more tenacious.

-White gold, whose composition consists of 90% gold with 10% of any white metal, such as silver or palladium.

References

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2. Nippon Steel & Sumitomo Metal Corporation. (2012). Non-Ferrous Structural Materials (Titanium, Aluminum).. Recovered from: nipponsteel.com
3. WA Monteiro, SJ Buso and LV da Silva (2012). Application of Magnesium Alloys in Transport, New Features on Magnesium Alloys, Waldemar Alfredo Monteiro, IntechOpen, DOI: 10.5772 / 48273.
4. Copper Development Association. (2018). Copper and Copper Alloys. Recovered from: copperalliance.org.uk
5. Michael Oistacher. (March 7, 2018). Silver Alloys and their Uses. Recovered from: mgsrefining.com
6. Terrence Bell. (September 26, 2018). Beryllium Applications. Recovered from: thebalance.com
7. Cosmolinux. (sf). Activities Phase diagrams. Recovered from: cosmolinux.no-ip.org