Metal Properties Explained: Essential Characteristics and Applications You Should Know

With thousands of different metal alloys, it’s important to know when to use and when not to use each one. The key factors in making such a decision rely on the metal’s properties and characteristics, and your project’s needs.

Therefore, to select the correct metal, you must first understand the importance of the various properties a material can have. In this blog, we take a look at these, from tensile strength to corrosion resistance and everything in between.

Mechanical Properties of Metals

The mechanical properties of metals are often the most important, as they affect how the material will perform in service and how easy it is to manufacture. These are some of the most important mechanical properties to consider:

Strength

Probably the first and foremost property that springs to mind when comparing metals is strength. There are a few different ways to quantify strength in a material.

Yield Strength

When a metal experiences stress, it deforms; this could be a cable stretching or a beam bending. The point at which the object will no longer return to its original shape after the load is released defines its Yield Strength.

This is the property most commonly used as a guide to the overall strength of a metal, as it gives a good insight into the useful and functional strength. Whilst steel is considered pretty strong, more exotic alloys such as Titanium are even stronger.

Ultimate Tensile Strength

The UTS of a metal is the maximum amount of stress the material can withstand. This point is after the yield point and is defined by the point at which the material begins to “neck”, that is, drastically thin out before fracture.

Ductility

Ductility, or how Ductile a metal is, is the ability for it to deform without breaking. It might sound counterintuitive, but ductility is a useful property in structures, with a certain degree of ductility being required to avoid instant failure.

Ductility is also an important property to take into account when assessing workability. Many processes, such as bending and forming, rely on a material being ductile enough not to fracture.

Some materials that are revered for their ductility are aluminium and copper, these are great for drawing into thin wires.

Toughness

Toughness is often used interchangeably with the term Impact Strength; in reality, they are related but not identical. Toughness is the ability of a material to absorb energy without fracturing. It is related to both strength and ductility.

Numerous alloys of steel are incredibly tough, common uses include military armor on vehicles and buildings.

Hardness

Hardness is the ability of a metal to resist localised deformation. A material with higher hardness will be harder to scratch or indent, but it is not necessarily stronger than a metal with a lower hardness value.

High carbon steel has high hardness levels, hence its use in making drills and machining tools.

Fatigue Resistance

Fatigue resistance is the ability of a material to resist breaking under cyclical loading. Fatigue is a large consideration for certain applications, as it can cause parts to break at stress levels much lower than expected.

Creep Resistance

In a similar manner to Fatigue Resistance, Creep resistance is the ability of a material to withstand plastic deformation or failure after an extended period of stress. Creep is often also witnessed at high temperatures, meaning metals that are also temperature resistant are often better at resisting creep.

Superalloys of steel and cobalt are often used in things like jet turbine engines, for their strength and creep resistance.

Other Properties of Metals

Alongside how they perform under stress, impact or abrasion, metals also differ between the types in how they respond to other stimuli, such as heat, electricity and a corrosive environment. Before selecting a material, consider the following:

Corrosion resistance

Corrosion is the act of a substance being eroded away and weakened by an unintended chemical reaction. The most common type is rust, the corrosion of Iron and steel. Some metals are inherently resistant to corrosion, thanks to their alloying elements.

Stainless steel is probably the most well-known corrosion resistant metal.

Temperature Resistance

Both high and low temperatures can have a detrimental effect on metals, with the former enabling creep and the latter increasing brittleness in certain alloys. Both the alloying elements and crystal structure can affect the performance of the metal.

Electrical and Heat Conductivity

One of the characteristics that defines a metal is that it has free moving electrons, enabling it to conduct electricity and heat. However, some metals are much better conductors than others. If a metal is to be used as a conductor in an electrical system, the conductivity and therefore the resistance are important considerations.

Copper and Aluminum are both used for electrical conductors.

Density

Not all metals weigh the same per unit volume, the density varies greatly across all metals. This not only has an effect on other mechanical characteristics, but it also affects the weight of a finished product.

Strength to Weight ratio

Closely linked to the aforementioned density, the strength to weight ratio is an important factor if your component needs to be both strong and lightweight. Certain materials, even though they are not as strong pound-for-pound, have a higher strength to weight ratio.

Titanium has one of the highest strength to weight ratios of any metal.

Common Applications of Metals

Whilst there are 94 different metals on the periodic table, besides alloying being used as alloying elements, the commonly used metals in industry are limited to a select few.

Metals can be found in almost every aspect of life, from the buildings we live and work into the bridges and other infrastructure that keep the world mobile. Furthermore, almost all modern appliances use metal to some degree, be that mobile phones, microwaves or microchips.