CASTING:

It is one of the most ancient process of manufacturing metallic components. It is the first step in manufacturing metallic components.

It can be defined as process of producing metal parts by pouring the molten metal into the mould cavity of the required shape and allowing the metal to solidify. The solidified metal piece is called as ‘’casting’’.

Types of casting:

 

Steps involved in casting:

• Making the pattern of the part with all details.
• Making a mould by packing the sand around the pattern and then removing the pattern to leave a cavity.
• Inserting the cores if required.
• Melting and pouring the molten metal into mould. After solidification casting is removed from the mould.
• Fettling and inspection of casting.
• Further processing (machining and finishing) if required.

Advantages:

1. Parts of intricate shapes can be produced.
2. Almost all the metals and alloys and some plastics can be cast.
3. A part can be made almost to the finished shape before any machining is done.
4. Good mechanical and service properties.
5. Mechanical and automated casting processes help decrease the cost of casting.
6. The number of castings can vary from very few to several thousands.

Disadvantages:

1. Lot of molten metal is wasted in riser and gating.
2. Casting may require machining to remove rough surfaces.
3. Some defects occur in the casting like blow holes, misrun, run out, mismatch etc if casting process not properly followed.

Engineering Materials

 Materials:

Material this is a very familiar word to all of us. For our daily applications and need and most important thing for our survivals we are using this materials. In the time of our human life began on this earth we use some materials like stone, wood, bone, fur etc. With the help of that the first man and his families survive their life in many aspects. Gold was first metal used by the mankind followed by copper. Based on these metals we divided our time or survival on this earth like bronze age, iron age.

General definition:

Materials = Substance of which something is composed or made.

Engineering Material: Part of inanimate matter, which is useful to engineer in the practice of his profession (used to produce products according to the needs and demand of society).

Material Science: Primarily concerned with the search for basic knowledge about internal structure, properties and processing of materials and their complex interactions/relationships.

Material Engineering: Mainly concerned with the use of fundamental and applied knowledge of materials, so that they may be converted into products, as needed or desired by the society (bridges materials knowledge from basic sciences to engineering disciplines). 

Importance of materials in Technologies/Manufacturing:

In view of technologies/manufacturing, engineering or work of engineer is a crucial part. Whatever engineering it may be they made or discover new ideas and solutions, they use this materials and material engineering and this material science concepts. Like for example....

• In stream of mechanical engineering they use the materials which are suitable for withstand in high load, high temperature and high wear conditions.
• Electrical engineers search for materials by which electrical devices or machines can be operated at a faster rate with minimum power losses.
• Aerospace & automobile engineers search for materials having high strength with less weight because of that they can reduce the fuel consumption and obtaining more performance. 
• Electronic engineers search for material that are useful in the making of electrical devices r circuits.
• Chemical engineers search for materials which are not chemically reactive to other materials and high corrosion resistance materials.

Classification of Materials:

materials can be classified according to the 

1. General Properties.

2. Nature of Materials.

3. Applications.

According to General Properties:

a. Metals:

i. Ferrous Metals : Iron is a base metal and remining small amount is the carbon and other elements.

    Example: Steel, Cast Irons

ii. Non Ferrous: in this type metals we cant observe iron in their composition. so non ferrous metals are the iron free metals. we can simple say that rest of all other metals and their alloys. Example: Aluminum, Copper, Zinc etc... Alloys like Brass, Bronzes Duralumin etc..

b. Non Metals:

   Which materials don't have any composition of metals those we called it as non metals. Like Leather, Rubber, Asbestos, Plastics etc..

According to Nature of Materials:

1. Metals
2. Ceramics
3. Polymers
4. Electronic Materials
5. Composites
6. Biomaterials
7. Advanced/Smart Materials

According to Applications:

1. Electrical Materials: e.g. conductors, insulators, dielectrics, etc 
2. Electronic Materials: e.g. conductors, semi-conductors, etc 
3. Magnetic Materials: e.g. ferromagnetic, paramagnetic & diamagnetic materials, etc 
4. Optical Materials: e.g. glass, quartz, etc 
5. Bio Materials: e.g. man-made proteins, artificial bacterium

Properties of Metals, Ceramics and Polymers:        

Metals		Ceramics		Polymers
Metals like Fe, Al, Cu etc.		Ceramics are inorganic compounds and are usually made either of oxides, carbides, nitrides or silicates of metals.		Polymers are materials made of long, repeating chains of molecules. These are based on H, C and other non metallic elements.
Metallic bonding		Ionic and Covalent bonding		Covalent bonding
Binding Energy is high		Powder made materials		Binding Energy is low
Strength is high		Strength is in between metals and polymers		Strength is low
Distance between atoms is less.		Distance between atoms is in between those of metals and polymers		Distance between atoms is large.
Corrosive in nature		Anti corrosive in nature		Anti corrosive in nature
Density is high		Density is in between metals and polymers		Density is low
Service temperature around 600-12000C	is	Service      temperature around 30000C.	is	Service       temperature around 3000C.	is
Thermally good conductors		Thermal Insulators		Thermally bad conductors
Electrically good conductors		Electrical Insulators		Partially               Electrical conductors

Properties of Materials: 

It is important to study the properties of the materials and know how the properties of the materials are affected during the use of the material in a component. Also the properties of the materials help an engineer in selecting suitable material for a particular application. The properties of materials can be:

• Physical Properties
•  Chemical Properties
•  Thermal Properties
•  Electrical Properties
•  Magnetic Properties
•  Optical Properties
•  Mechanical Properties 

Mechanical Properties:

For a mechanical engineer, the mechanical properties are important. The mechanical properties are the properties (traits) exhibited by the material when a force is applied on the material. The common  mechanical properties that are interests to a mechanical engineer are

Strength, Ductility, Malleability, Hardness, brittleness, Toughness, Resilience, Creep, fatigue etc.

 Strength: It is the ability of the material to withstand the external load. It can also be defined as an ability of material to resist the applied external load without fracture or excessive deformation. The strength of the material can be tensile strength, compressive strength, shear strength etc.

Stiffness: Stiffness is basically the resistance offered by an elastic body to deflection or deformation by an applied force. It is the resistance of a material towards the elastic deformation and is expressed by the Young’s Modulus or Modulus of elasticity.

Ductility: The ability of the material to exhibit large plastic deformation prior to fracture under tensile load is known as ductility. (Or ) The ability of a material to be drawn into wires is known as ductility and is expressed in terms of percentage elongation.

Malleability: The ability of the material to exhibit large plastic deformation prior to fracture under compressive load is known as malleability. (Or ) The ability of a material to be drawn into sheets is known as malleability. It is expressed in terms of percentage reduction in cross-section of the material.

Brittleness: It is the ability of the material to undergo sudden failure or fracture without appreciable deformation and without entering into plastic deformation zone.

Hardness: The resistance offered by the material towards indentation or deformation is called hardness. The hardness of a material can be expressed in various ways. The most common hardens is the indentation hardness.

Toughness: The total energy absorbed by the material before fracture is called toughness. The total energy is usually sum of the elastic and plastic energy.

Resilience: It is the ability of the material that can resist shock or impact loads.

 Creep: Slow and progressive deformation of a material with time under constant stress is called creep.

Fatigue: Time Vs strain behavior of a material under oscillating loading conditions. It is the tendency leading to fracture under cyclic (repeated) or fluctuating stresses.

Essential Elements in Materials Science:

 There are four essential elements in materials science and engineering.

1.  Processing / Synthesis
2.   Structure / Composition
3.  Properties and
4.  Performance /Application

The interrelation between the above four elements is given in Fig.