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Alloys and composites are mixtures of different elements and differ in terms of their composition. An alloy has at least one metal in its composition while composites have no metallic component. Alloys with clearly defined crystal structures and stoichiometry are referred to as intermetallic compounds.
Alloys are metals that are not pure elements. There are no chemical bonds present in them imparting them their special properties. Composites have a matrix and a strengthening phase. The key role of the matrix is to hold the strengthening phase together. Carbon-reinforced polymers are a classic example of composites.
Read More: Properties of Metals & Non-Metals
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Key Terms: Alloy, Composite, Brass, Bronze, Polymer, Alnico, Lustre, Homogeneous, Heterogeneous, Metals
Difference between Alloys and Composites
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Alloys and composites are different in their composition. This difference is responsible for the difference in their physical and chemical properties. Listed below are some important differences between alloys and composites:
| Parameters | Alloy | Composite |
|---|---|---|
| Composition | Alloy is a homogenous or heterogenous mixture of one or more metals with another element. | Composite is always a heterogeneous mixture of two or more elements that are not metals. |
| Electrical Conductivity | Presence of metals makes them a good conductor of electricity | Only Polymers are good conductors, while others are insulators. |
| Bonding | No bonding between the elements | Internal Bonding between the elements is present. |
| Occurrence | Alloys are rarely found in nature. | Composites are commonly found in nature. |
| Lustrous | Alloys are lustrous due to their metallic parent and have a shiny surface. | Composites do not have any lustrous or shiny surface due to the absence of metal. |
| Chemical Processing | Alloys do not undergo any chemical reaction as the elements are mixed in ratios. | Chemical reaction is involved in the formation of composites. |
| Quality | The improved quality of alloys can be noted in addition to the existing ones due to the addition of metal. | Composites have less improved quality than alloys. |
| Boiling Point | Boiling Point of alloys varies according to the metallic parent and alloying element. | Composites have a definite boiling point. |
| Melting Point | Melting point of the alloys varies greatly. | Composites have a definite melting point. |
| Examples | Steel, Bronze, Brass etc. | Human Bones, Fiberglass, Resin etc. |
Alloy Vs Composite
Read More: Metallurgy
What are Alloys?
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An alloy is a homogeneous material that can be made by melting two or more elements, one of which is a metal.
The participating metal is called the parent metal, which serves as the base metal for the alloying element, and is considered an alloying agent for most substances. The alloying agent can be a non-metal or metal in which the contribution or proportion is very small.
Alloys have completely new characteristics, different from their components:
- More favorable mechanical properties- low density, high strength
- Increased corrosion resistance- resistance to abrasion and corrosion
- Color change- shiny due to the presence of a metallic component in their composition.
- Improved processability- more desirable properties than those of the constituent
Alloy Structure
Examples of Alloys
- Steel – is an alloy of Iron and Carbon
- Brass - is an alloy of Zinc and Copper
- Bronze - is an alloy of Copper and Tin
- Nichrome – is an alloy of Nickel, Chromium, and Iron
- Amalgam – is an alloy of mercury and sodium
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| Concepts Related to Alloys and Composites | ||
|---|---|---|
| Non-Metal Oxides | Alkali Metals | Group-2 Elements |
| Thermal Conductivity | Metals & Non-Metals | Non-Metals |
| Occurrence of Metals | Amphoteric Oxides | Sedimentary Rocks |
Uses of Alloys
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Some of the most common uses of the alloy are listed below:
- Brass: Used to make kitchenware, screws, locks, door handles, electrical appliances, zippers, musical instruments, decorations, and gifts.
- Bronze: Used to make statues, coins, medals, kitchen utensils, and musical instruments, among other things.
- Alnico: Used as a ferromagnetic substance and in permanent magnets.
- Sterling Silver: Used in surgical equipment, musical instruments, cutlery, and jewelry
- Stainless Steel: Used to build railways, bridges, roads, airports, etc. It is also used to make kitchen utensils and other products.
- Aluminum Alloys: Used in the construction of fuselages and their components as they are lightweight.
Read More: Metals & Non-Metals Formula
What are Composites?
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Composites are usually a combination of two or more elements, but their structure does not include metals. Composites are heterogeneous, unlike alloys. Most synthetic materials are encountered naturally while others are manufactured.
Composites are made up of components with different physical properties. Some of the interesting properties of composites are:
- High strength
- Modulus
- Low density
- Excellent resistance to fatigue, creep rupture, corrosion, and wear
- Low coefficient of thermal expansion
Composite Materials
Composites are divided into two main categories:
- Ceramics
- Polymers
Examples of Composites
Some of the classic examples of composites are Wood, human body bones, fiberglass etc.
- Hard emery aluminum particles of aluminum oxide or silicon carbide bonded to glass
- Resin (epoxy or polyester resin) reinforced with fiberglass
- Composite structures - alternating layers of plywood consisting of thin layers of wood and wood glue (polymers).
Read More: Metals & Non-Metals Important Questions
Uses of Composites
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Some of the most common applications of composites in everyday life are buildings, bridges, and other constructions including boat hulls, swimming pool panels, racing car bodywork, bathtubs, storage tanks, and vanities are made of composite materials.
Read More: Metal & Non-Metal Revision Notes
Difference between Steel Toe and Alloy
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Listed below are some important differences between the steel tow and alloys:
- Protection to feet: Steel toes are heavy and provide better protection in comparison to lightweight alloys.
- Comfort: Steel toes are not comfortable for long-time wear in comparison to allows which are easy and comfortable to wear.
- Heat & Water Resistance: Steel toes have better heat and water resistance than alloy.
- Life: Steel toes are longer lasting in comparison to alloys.
- Cost: Steel toes are available at affordable prices in comparison to alloys that are expensive.
- Conduction: Cannot be worn by workers in fields as both steel toe and alloy are good conductors of electricity
- Origin: Steel toes have been used for more than 80 years now but alloys gained popularity owing to their comforts and design.
Read More: Sodium Sulfide
Handwritten Notes
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Provided below are some important handwritten notes covering important concepts from Metals and Non-metals.
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Things to Remember
- An alloy can be created by melting two or more elements to create a homogenous substance.
- It involves an alloying agent and a parent metal, which acts as the base metal for the alloying element.
- The characteristics of alloy are improved conductivity, color change, and higher corrosion resistance.
- Steel, bronze, brass, amalgam, etc. are examples of alloys.
- Composite lack metals in their structural makeup but combine two or more components.
- Interesting properties of Composites are low density, high strength and exceptional resistance to corrosion
- Examples of composites are Human bones, epoxy, resin, fiberglass, etc.
Read More:
| Important Concepts on Metals & Non-Metals | ||
|---|---|---|
| Transition Metals | Inner Transition Metals | Halides |
| Beryllium | Refining of Metals | Nickel Sulphate |
| Reactivity Series | NCERT Solutions: Metals & Non-Metals | Barium |
Sample Questions
Ques. Which property of alloys talks about their stability? (1 mark)
Ans. Low thermal expansion in alloys is due to their dimension stability.
Ques. What is the composition of Steel, Bronze, and Brass alloys? (3 marks)
Ans. The composition of the following alloys is as follows –
- Steel - is an alloy of Iron and Carbon
- Bronze- is an alloy of Copper and Tin
- Brass - is an alloy of Zinc and Copper
Ques. Write the major differentiating point between alloys and composite materials. (2 marks)
Ans. Alloys are made by homogeneously mixing metals and elements, while composites are systems composed of two or more components with different configurations, one of which is the matrix or the base material (polymer, ceramic or metal), to which the second component is added.
Ques. Mention the example of Composites. (2 marks)
Ans. Examples of Composites are Wood, Body Bones, Hard emery aluminum particles of aluminum oxide or silicon carbide bonded to the glass, Resin reinforced with fiberglass.
Ques. Write the difference between Alloy and Composite. (4 marks)
Ans.
| Parameters | Alloy | Composite |
|---|---|---|
| Define | Alloy is a homogenous mixture of metals or a mixture of a metal and another element. | Composite is a mixture of two or more elements for which the metal is not essentially required. |
| Conductivity | Good Conductor | Only Polymers are Conductors, while others are insulator. |
| Bond Arrangement | No bonding between the elements | Internal Bonding between the elements is present. |
| Example | Steel, Bronze, Brass etc. | Human Bones, Fiber glass, Resin etc. |
Ques. What are the properties of Alloys? (2 marks)
Ans. Alloys on formation acquire new properties as follows:
- Low density
- High strength
- Resistance to abrasion and corrosion.
Ques. What will be the change when adding chromium to steel which of the following property is enhanced? (2 marks)
Ans. Resistance to corrosion is due to results in the formation of a thin, chemically stable, and passive oxide film. The oxide film forms and heals itself in the presence of oxygen.
Ques. Which is the alloy used for dental filling? (1 mark)
Ans. Amalgam – an alloy of mercury and sodium, is used in the dental filling because it is strong and long-lasting.
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