What is the toughest metal found on Earth?

To identify the strongest metal on Earth, we must first establish some criteria. There are several ways to assess a metal's strength.

Tensile strength, measured in pounds per square inch (psi), indicates the maximum load a material can endure without failing. Yield strength shows how much stress is needed to cause permanent deformation.

Tungsten boasts the highest yield and tensile strength of any pure metal, which makes it arguably the toughest metal on Earth. However, it is not the hardest metallic element or even the strongest metal by weight.

When discussing pure metals, it also raises the question: Does the strongest metal have to be a natural, unalloyed metal, or can it be an alloy composed of different metals? Steel is widely regarded as the strongest alloy on Earth.

Let’s examine some of the strongest metals on Earth and the surprising ways they are used.

Tungsten

Tungsten has the highest melting point (3695 K) and ultimate tensile strength (142,000 psi) of any natural metal. Tungsten and its alloys have been used in manufacturing filaments for incandescent bulbs and TV tubes.

Tungsten on its own ranks 7.5 on the Mohs scale of hardness, where diamond reaches a perfect 10. However, when combined with carbon to form tungsten carbide, its hardness increases significantly to 9.5, making it ideal for producing durable tools.

Steel

Steel is a mixture of iron (a metal) and carbon (a nonmetal). The proportion of iron and carbon in the alloy can vary, as well as the inclusion of other metals. For instance, adding chromium to steel results in stainless steel, while carbon steel has a higher carbon content, enhancing its strength compared to other types of steel.

Osmium

Osmium is one of the heaviest naturally occurring metals, making it extremely dense. Despite this, osmium is fragile and is therefore used in small amounts when combined with other metals in alloys. It is commonly found in electrical circuits.

Chromium

When considering strength in terms of hardness, chromium may well be the toughest metal around. Scoring a solid 8.5 on the Mohs scale, chromium is the hardest metal on the planet. Its ability to resist corrosion is another reason it's often used for chrome plating.

Titanium

Titanium, named after the mighty Titans of Greek mythology, possesses the highest strength-to-density ratio of any metal. Alloys made from titanium, when combined with other metals, have the best strength-to-weight ratio known. In its pure form, titanium is as strong as steel but weighs 45% less.

The remarkable strength-to-weight ratio of titanium alloys makes them the preferred materials for airplane engines, aircraft bodies, rockets, and missiles — essentially any application requiring lightweight yet tough metal components. While titanium is not especially rare, it is costly due to the expensive mining and production processes involved.

The Airbus A380, the largest passenger jet in existence, contains a remarkable 77 tons (70 metric tons) of titanium, primarily utilized in its enormous engines.

A breakthrough in metallurgy during the 1930s, known as the "Knox process," paved the way for commercial titanium forging to flourish in the 1940s and 1950s. Initially, titanium was used in military aircraft and submarines (for both the U.S. and Russia), before being incorporated into civilian planes in the 1960s.

The Discovery of Titanium

In 1791, an amateur British mineralogist and church pastor, William Gregor, found an intriguing black sand in a stream near Cornwall. While some of the sand was magnetic and identified as iron oxide, the rest was a mystery. It was another oxide, but one that wasn't listed in the Royal Geological Society's records.

In 1795, German chemist Martin Heinrich Klaproth rediscovered the unusual oxide and named it titanium oxide, after the Titans from Greek mythology, who were the deities that preceded the Olympians.

Although titanium was first discovered in the late 1700s, it wasn't until 1910 that pure titanium was successfully extracted from its oxide. This breakthrough came courtesy of American chemist Matthew Hunter, who, working for General Electric, developed a method to separate the lustrous metal from its oxide using intense heat and pressure inside a sealed ‘bomb.’

Titanium Resists Rusting

Corrosion is a slow, electrochemical process that gradually degrades most metals over time. When metals are exposed to oxygen, either in the air or beneath water, the oxygen captures electrons, leading to the formation of what are known as metal ‘oxides.’ A prime example of this is iron oxide, or rust.

However, not all oxides cause the metal beneath them to corrode. When titanium reacts with oxygen, it forms a protective layer of titanium dioxide (TiO2) on its surface. This oxide layer acts as a shield, safeguarding the titanium from corrosion due to most acids, alkalis, pollutants, and even saltwater.

Due to its innate resistance to corrosion, titanium is not only the perfect material for aircraft, but also for marine components exposed to the highly corrosive effects of saltwater. As a result, titanium is commonly used for ship propellers, internal ballast and piping systems, as well as hardware on ships that come into contact with seawater.

Titanium is found in various parts of the human body, from head to toe.

The same thin titanium dioxide layer that shields titanium from corrosion also makes it the safest material to be used for medical implants. Titanium is known for being 'biocompatible,' meaning it is non-toxic, non-allergenic, and even capable of bonding with human tissue and bone.

Titanium is the preferred material for a wide range of surgical implants, including those for bones and joints, cranial plates, dental implant roots, artificial eye and ear pegs, heart valves, spinal fusions, and even urethral stents. 'Studies have shown' that titanium implants stimulate the body’s immune system to promote the growth of bone directly onto the titanium surface, a process called osseointegration.

Titanium is also favored for hip replacements and fracture pins because of its remarkable strength-to-weight ratio, which ensures that the implants remain lightweight, while also matching the same elasticity as human bone.

Titanium is commonly used in golf clubs and various other sports equipment due to its unique properties.

As the cost of pure titanium decreased in the late 20th century, manufacturers began exploring more commercial uses for this remarkable metal. Its lightweight yet durable nature made titanium an ideal choice for sporting goods.

The first titanium golf clubs were introduced in the mid-1990s, including a massive driver from Callaway called Great Big Bertha. Although these clubs were pricier than their steel or wood counterparts, their success inspired other sports equipment manufacturers to experiment with titanium.

Today, titanium can be found in almost any sports equipment where strength, durability, and weight are crucial: tennis rackets, lacrosse sticks, skis, bicycle frames, baseball bats, hiking and climbing gear, camping supplies, and even horseshoes used in professional racehorses.

Titanium is also found in white paint (and even cake icing).

Only 5 percent of the 6.3 million tons (5.7 million metric tons) of titanium produced annually is processed into metal. The rest is transformed into titanium dioxide, the same substance that naturally protects titanium from corrosion. This titanium dioxide is widely used as a non-toxic whitening agent in paint, cosmetics, medicines, and food, including white cake icing.

White paint was once made using a lead-based pigment, but after the health risks of lead became widely known, titanium dioxide replaced it. It turns out that titanium-based pigments have some fascinating properties.

House painters prefer titanium-based white paints because they are resistant to corrosion and have a longer lifespan. Titanium oxide is highly refractive, giving the paint a natural brilliance 'greater than a diamond' and producing an exceptionally bright white shade.

Titanium oxide also reflects infrared light, which is why it is used in the exterior coatings of solar observatories, helping to scatter infrared light that could otherwise distort images.

Sources

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