Short Notes: Introduction of Engineering Materials | Short Notes for Mechanical Engineering PDF Download

 Page 1


Introduction of Engineering Materials
Materials are the substances from which things are composed. The fundamental 
science of materials looks at their structure and properties. Materials engineering 
is the processing and selection of materials. Processing -? Structure -? Properties 
-*¦ Application. (Read arrow as determines)
A material’s structure determines its properties which in turn determine the 
applications for which it can be used. However, with knowledge of the structure 
and some creativity, the engineer can formulate a process that will change the 
structure and enhance the properties, thereby enabling it to be used for a 
sophisticated application.
Classification of Materials
One way to classify materials is in these six categories:
1. Metals/Alloys
2. Ceramics
3. Glasses
4. Polymers
5. Composites
6. Semiconductors
An alternate classification of materials uses categories based on their properties:
1. Structural materials
2. Electronic materials
3. Magnetic materials
4. Semiconducting materials
5. Optical materials
Page 2


Introduction of Engineering Materials
Materials are the substances from which things are composed. The fundamental 
science of materials looks at their structure and properties. Materials engineering 
is the processing and selection of materials. Processing -? Structure -? Properties 
-*¦ Application. (Read arrow as determines)
A material’s structure determines its properties which in turn determine the 
applications for which it can be used. However, with knowledge of the structure 
and some creativity, the engineer can formulate a process that will change the 
structure and enhance the properties, thereby enabling it to be used for a 
sophisticated application.
Classification of Materials
One way to classify materials is in these six categories:
1. Metals/Alloys
2. Ceramics
3. Glasses
4. Polymers
5. Composites
6. Semiconductors
An alternate classification of materials uses categories based on their properties:
1. Structural materials
2. Electronic materials
3. Magnetic materials
4. Semiconducting materials
5. Optical materials
Metals/Alloys
• Structure:
° any metallic element /alloy (see periodic table)
° simple crystalline structure 
° metallic atomic bonding 
° delocalized electrons
• Properties:
o high conductivity
o not transparent to visible light (i.e. opaque)
° lustrous 
o strong 
o ductile
• Examples:
° iron (Fe)
° steel (Fe+C) 
o aluminum (Al) 
o copper(Cu)
° brass (Cu+Zn)
° magnesium (Mg) 
o titanium (Ti) 
o nickel (Ni)
° zinc (Zn)
Ceramics/ Glasses/ & Glass-Ceramics
• Structure:
° compounds of metals and non-metals (see periodic table)
° primarily ionic atomic bonding (however, these bonds might have some 
covalent character)
o ceramics are crystalline (crystalline structure can be relatively simple to 
relatively complex)
° glasses are amorphous (primarily made of Si02 )
° glass-ceramics are devitrified glasses
• Properties:
° insulative 
° refractory 
° wear resistant 
° brittle 
° strong 
° hard
° chemically stable 
° high melting temps 
° glasses are transparent
o gl-cer can have low thermal expansion (good for thermal stresses)
• Examples:
° oxides (Al203 , MgO, Si02 )
° nitrides (Si3N4)
° carbides 
° silicates
o lithium-alumino-silicates
Page 3


Introduction of Engineering Materials
Materials are the substances from which things are composed. The fundamental 
science of materials looks at their structure and properties. Materials engineering 
is the processing and selection of materials. Processing -? Structure -? Properties 
-*¦ Application. (Read arrow as determines)
A material’s structure determines its properties which in turn determine the 
applications for which it can be used. However, with knowledge of the structure 
and some creativity, the engineer can formulate a process that will change the 
structure and enhance the properties, thereby enabling it to be used for a 
sophisticated application.
Classification of Materials
One way to classify materials is in these six categories:
1. Metals/Alloys
2. Ceramics
3. Glasses
4. Polymers
5. Composites
6. Semiconductors
An alternate classification of materials uses categories based on their properties:
1. Structural materials
2. Electronic materials
3. Magnetic materials
4. Semiconducting materials
5. Optical materials
Metals/Alloys
• Structure:
° any metallic element /alloy (see periodic table)
° simple crystalline structure 
° metallic atomic bonding 
° delocalized electrons
• Properties:
o high conductivity
o not transparent to visible light (i.e. opaque)
° lustrous 
o strong 
o ductile
• Examples:
° iron (Fe)
° steel (Fe+C) 
o aluminum (Al) 
o copper(Cu)
° brass (Cu+Zn)
° magnesium (Mg) 
o titanium (Ti) 
o nickel (Ni)
° zinc (Zn)
Ceramics/ Glasses/ & Glass-Ceramics
• Structure:
° compounds of metals and non-metals (see periodic table)
° primarily ionic atomic bonding (however, these bonds might have some 
covalent character)
o ceramics are crystalline (crystalline structure can be relatively simple to 
relatively complex)
° glasses are amorphous (primarily made of Si02 )
° glass-ceramics are devitrified glasses
• Properties:
° insulative 
° refractory 
° wear resistant 
° brittle 
° strong 
° hard
° chemically stable 
° high melting temps 
° glasses are transparent
o gl-cer can have low thermal expansion (good for thermal stresses)
• Examples:
° oxides (Al203 , MgO, Si02 )
° nitrides (Si3N4)
° carbides 
° silicates
o lithium-alumino-silicates
o clay 
° cement
Polymers (aka Plastics)
• Structure:
° organic compounds primarily based on C and H.
° large molecular structures in a chain or network configuration 
° atomic bonding is covalent on the chains or network and additionally 
there is secondary bonds acting between the chains or network.
° 5-95% crystalline in relatively simple structures to very complex
• Properties:
° very ductile (elastic and plastic)
° low density 
° low strength 
° low melting temp 
° high chemical reactivity 
° insulative
• Examples:
° polyethylene 
° PVC 
° rubber 
° acrylics - 0 
° nylons - N 
° fluoroplastics - F 
° silicones-Si
Composites
• Structure:
° Engineered materials of more than one type, usually a matrix material 
with fibers or particulates
• Properties:
° Could be anything, depending on constituents, relative amounts and 
geometry.
° Examples:
° fiberglass 
° concrete 
° asphalt 
° wood
Semiconductors
• Structure:
° elemental (Group IVA)
° compound (Groups IIIA/VA or IIB/VIA)
° covalent/ionic bonding 
° similar to ceramics
• Properties:
° intermediate conductivity which is extremely sensitive to minute 
concentrations of impurities
Page 4


Introduction of Engineering Materials
Materials are the substances from which things are composed. The fundamental 
science of materials looks at their structure and properties. Materials engineering 
is the processing and selection of materials. Processing -? Structure -? Properties 
-*¦ Application. (Read arrow as determines)
A material’s structure determines its properties which in turn determine the 
applications for which it can be used. However, with knowledge of the structure 
and some creativity, the engineer can formulate a process that will change the 
structure and enhance the properties, thereby enabling it to be used for a 
sophisticated application.
Classification of Materials
One way to classify materials is in these six categories:
1. Metals/Alloys
2. Ceramics
3. Glasses
4. Polymers
5. Composites
6. Semiconductors
An alternate classification of materials uses categories based on their properties:
1. Structural materials
2. Electronic materials
3. Magnetic materials
4. Semiconducting materials
5. Optical materials
Metals/Alloys
• Structure:
° any metallic element /alloy (see periodic table)
° simple crystalline structure 
° metallic atomic bonding 
° delocalized electrons
• Properties:
o high conductivity
o not transparent to visible light (i.e. opaque)
° lustrous 
o strong 
o ductile
• Examples:
° iron (Fe)
° steel (Fe+C) 
o aluminum (Al) 
o copper(Cu)
° brass (Cu+Zn)
° magnesium (Mg) 
o titanium (Ti) 
o nickel (Ni)
° zinc (Zn)
Ceramics/ Glasses/ & Glass-Ceramics
• Structure:
° compounds of metals and non-metals (see periodic table)
° primarily ionic atomic bonding (however, these bonds might have some 
covalent character)
o ceramics are crystalline (crystalline structure can be relatively simple to 
relatively complex)
° glasses are amorphous (primarily made of Si02 )
° glass-ceramics are devitrified glasses
• Properties:
° insulative 
° refractory 
° wear resistant 
° brittle 
° strong 
° hard
° chemically stable 
° high melting temps 
° glasses are transparent
o gl-cer can have low thermal expansion (good for thermal stresses)
• Examples:
° oxides (Al203 , MgO, Si02 )
° nitrides (Si3N4)
° carbides 
° silicates
o lithium-alumino-silicates
o clay 
° cement
Polymers (aka Plastics)
• Structure:
° organic compounds primarily based on C and H.
° large molecular structures in a chain or network configuration 
° atomic bonding is covalent on the chains or network and additionally 
there is secondary bonds acting between the chains or network.
° 5-95% crystalline in relatively simple structures to very complex
• Properties:
° very ductile (elastic and plastic)
° low density 
° low strength 
° low melting temp 
° high chemical reactivity 
° insulative
• Examples:
° polyethylene 
° PVC 
° rubber 
° acrylics - 0 
° nylons - N 
° fluoroplastics - F 
° silicones-Si
Composites
• Structure:
° Engineered materials of more than one type, usually a matrix material 
with fibers or particulates
• Properties:
° Could be anything, depending on constituents, relative amounts and 
geometry.
° Examples:
° fiberglass 
° concrete 
° asphalt 
° wood
Semiconductors
• Structure:
° elemental (Group IVA)
° compound (Groups IIIA/VA or IIB/VIA)
° covalent/ionic bonding 
° similar to ceramics
• Properties:
° intermediate conductivity which is extremely sensitive to minute 
concentrations of impurities
° precise control of chemical purity allows precise control of electrical 
properties
° techniques exist to produce variations in chemical purity over very small 
spatial regions
° hence, sophisticated and minute circuitry can be produced in 
exceptionally small areas (This is what makes micro-circuitry possible in 
ICs)
• Examples:
° Si, Ge, Sn 
o CaS 
° GaAs