As an engineer, we must know the basics of the properties of metals. This helps in choosing the right metal for different applications. So let us learn more about the properties of metals in this article. At the end of this article, you will get a link for Properties of metals PDF, which you can download for your future reference.
What is properties of metals
Properties of metals can be defined as the unique and distinctive features that every metal owns. Every material has its special quality and characteristics. Some properties are available in the raw form of metals, and different processes like heat treatment can modify some to suit process needs.
Different Types Of Properties Of Metals
Frankly speaking, the properties of metals is a very vast subject. Covering each and every property may be out of the scope of this article. So in this article, we will only focus on only basic and main properties that you should know.
Below are few main and basic types properties of metals.
- Physical Properties
- Electrical Properties
- Thermal Properties
- Chemical Properties
- Magnetic Properties
You may also like to read: Properties of fluids
Physical Properties Of Metals
Mechanical properties of metals or physical properties of metals can be defined as the natural behavior of metals under different loading conditions. It is the property of metals that offers resistance to failure when it is exposed to real-life applications.
When metals are exposed to load, it gets stressed. If you increase the load, metals get more stressed and the state of metals also gets changed. In different states metals have different properties.
Here are couple of mechanical properties of metals.
The ductility of metals can be defined as the property of metals to form into different shapes like wire. The metal gets elongated before it fails.
Ductility is an important property of metals. If the metal is not ductile you can not give it a different shape which means that it will have limited real-life applications. The ductility of metals can be improved by different heat treatment techniques.
Toughness is the property of metals that absorb energy and plastically deform without fracturing. Toughness required metals to be ductile as well as strong.
The toughness of metals can be defined as the energy per unit volume that it can absorb before failure. A typical application of tougher material is turret press, hammer, power press, etc.
Hardness is the property of metal to resist local plastic deformation due to mechanical indentation or abrasion .
The hardness of metal depends on its ductility, plasticity, elasticity, and toughness. There are usually three ways, hardness can be measured for a metal.
- Scratch hardness
- Indentation hardness
- Rebound hardness
Brittleness is the property of a metal to resist fracture. Usually, if a metal is less ductile, it is more brittle. Brittle metals it has a little elastic or plastic deformation. When more load is applied it easily gets fractured.
Elasticity is the property of metals that helps metals to regain its shape when the load is removed. We all know that metals deform when an external load is applied. But when that load is removed metals should go back to their original shape and that is called elasticity.
Most of the cutting tools have a certain level of elastic properties. Those tools have a limit of load that you can apply. Beyond that, the tool will go into permanent deformation and won’t go back to the actual shape. Elasticity is a very critical property of the metal. Without elastic property, metals will easily fracture with a very minimum load.
When metals go beyond its elastic limit, it goes into the plastic limit. So plasticity is the property of metals that keeps the metal in the plastic state without permanent deformation. Even if you remove the load, the metal won’t be able to go back to its original shape. But at the same time, there is no permanent deformation or fracture.
Most of the sheet metal operations like shearing, bending, etc is possible due to the good plasticity of sheet metal. Most of the rolling and forging operations are also done when the metal is in a plastic state.
Stiffness is the rigidity of metals. What that means is that even with extreme load those metals won’t deform. So stiffer metals won’t be having any elasticity of plasticity. Sometimes you need metals to be stiffer. For example, machine beds. Machine beds need to be stiffer as you don’t expect them to deform. If it does deform then it will affect the machine’s accuracy and alignment.
Did you notice how old the mechanical clock used to store energy? Old mechanical clocks use a spring that stores energy. So the property due to which the spring metals could store energy is called resilience. More the resilience, the more it can store energy and absorb impact strength.
Resilience is measured as the amount of energy it can store in a unit volume of metals. Usually, springs use high resilience metals.
Creep can also be associated with durability. Creep decides how long metal can last with a continuous force acting on it. Metals having good creep value will be able to withstand constant load for a longer period of time before it fails.
Let’s take an example of engine metal parts. Those should be made of metals with good creep value. So that those do not fail and engines also last longer.
Malleability is the property of metals by virtue of which it can undergo severe compressive stress without getting fractured.
You may also like to read: Heat treatment process
Electrical Properties Of Metals
The electrical properties of metals decide if the metal can conduct or resist electricity or it offers insulation to electricity. Below are the types of electrical properties of metals that we should know.
- Dielectric strength
Conductivity is a property of metals by virtue of which you can say how good the metal is for electricity transmission. If the metal has good conductivity it is better suited for electricity. If the metal does not have electric conductivity, then it is called insulators.
Copper and aluminum are two widely used metals known for good electric conductivity. Since both are ductile, so they are used in manufacturing electric wires and equipment.
Resistivity is the opposite of conductivity. So resistivity defines how good the metal is to resist electric conductivity. That does not mean that those metals can not transmit electricity, they can, but they always offer some resistivity and are not good for electric conductivity.
We all know that metals that do not allow electric conductivity are called insulators. But please make a note those are insulator to electricity only at room temperature. If you keep on increasing the voltage, there will be a limit beyond which the metals lose their insulation properties and start conducting electricity.
So dielectric strength of metals is the minimum voltage at which those metals become conductive from being an insulator. This property is very crucial when we design any electric components. Otherwise even a good insulator may fail and we will run into safety issues.
Thermal Properties Of Metals
The thermal properties of metals define how good is the metal under heat. For example, some metals expand, and some other contract under heat. That affects the overall stability of a part and a product. Knowing the thermal properties of metals is essential while designing a product failing in which the product may also fail. Below are a couple of key thermal properties of metals.
- Thermal Conductivity
- Thermal Expansion
- Specific Heat
- Melting Point
- Latent heat of fusion
Thermal conductivity decides how well a metal can transfer heat energy. The more the thermal conductivity, the better the metal is for transferring heat energy. For example, aluminum can quickly heat up and dissipates heat compare to steel. That is why you may notice aluminum insulation or wrapper in industrial applications.
Almost every metal expands under heat. Now how much it expands is the key thing. Consider you have designed a part without considering how much the part will expand under heat. When that part is exposed to heat, dimensions change and that part no longer will be able to fit into the product. The expansion or the contraction of metal is directly proportional to the amount of heat that is applied.
Specific heat of metal can be defined as the heat required to raise the temperature of a unit mass of a metal substance by one-degree celcius.
Melting point is the temperature at which metals start melting. It gives an overview of when the part may start melting.
Latent Heat Of Fusion
Latent heat of fusion is the heat required to a solid body at its melting point to convert it from solid to liquid.
Chemical Properties Of Metals
When we talk about the chemical properties of metals, we may pre-assume that it’s all about corrosion. But it is not. Do you know that in many countries, you can not use certain metal and plastic which may come into contact with human or food items? Passing toxicity tests is one of the big hurdles of many engineers when they design a product. So here are a couple of key chemical properties of metals that we should be aware of.
- Chemical Composition
Toxicity of metals or the toxic effect of metal can be defined as those properties which can cause harm to human or animal lives. This is purely due to the toxic composition of metals that poses the threat. Do you know that, in the United States, you need to mention how much Lead you have used in your house construction as lead is considered to be a toxic metal?
Corrosion is the natural process of refined metals to go back to a more fragile and pure state. Metal surfaces get damaged due to chemical process when it comes in contact with air and water. How much metal will degrade due to corrosion depends on the composition of metals?
Chemical composition decides if the metal is toxic or prone to corrosion. Many properties of metals depend on the composition of metals. Often it is found that metals in the raw form have poor chemical composition. Various metal treatment process like heat treatment is used to alter the chemical composition.
Magnetic Properties Of Metals
Magnetic properties of metals indicate how easily a metal can be magnetite and how it can retain the magnetic properties. The following are the key magnetic properties of metals.
- Coercive force
Permeability is the properties of metals by virtue of which you can magnetite a metal. High permeability means you can easily magnetite that metal. Usually, hard metals have low permeability and tough to magnetite. Soft metals have high permeability and easy to magnetite.
The coercive force also called magnetic coercivity is the measure of the ability of a metal to withstand a magnetic force without getting demagnetize.
When a metal is subjected to gradually increasing magnetic forces, the intensity of magnetization also get increases proportionally but with a lag. What that means is that, if you reduce the magnetic force to zero, the intensity of magnetization does not come down to zero. To make zero intensity of magnetization, you need to apply some reverse magnetic forces. This phenomenon is called hysteresis.
Properties of metals have a great impact on how it may perform in a real-life scenario. The properties of metals vastly depend on the composition and this can be altered by converting it to alloys or doing some heat-treatment process.
These are some of the key properties of metals that we should be aware of. For sure, when you actually work on projects, you may need to investigate many other properties. If you come across such scenarios, please do write in the comment section and I will be happy to assist.
Frequently Asked Questions (FAQ)
What are mechanical properties of metals?
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Latent heat of fusion
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