Engineering materials Flashcards
What are the main types of engineering materials?
- Metals and alloys
- Ceramics
- Composites
- Polymers
What are metals?
Elements that form positive ions by losing electrons during chemical reactions are called metals – electropositive entities with low ionization energies.
Name of scientist who proposed sea of electron theory.
Paul Drüde
What are the factors that affect metallic bonding?
- Magnitude of positive charge
- Number of delocalized electrons
- Ionic radius
Why are metals ductile and malleable?
Delocalized electrons allow metals to be deformed without fracturing.
Why are metals shiny?
Metals are shiny due to the excitation and deexcitation of delocalized electrons.
What are alloys?
In alloys, atoms of varying sizes are dispersed within the metallic lattice making it harder, less malleable and less ductile.
How do impurities affect melting point?
They decrease melting point.
What are some metals that can be alloyed with aluminum?
copper, manganese, silicon, magnesium,
zinc.
What are ceremics?
Made of metals and non-metals. May contain both covalent and ionic bonds. They can be amorphous (glass) or crystalline (other ceramics) in nature.
What is the particle size in particulate composites?
Particle size < 0.25 μm
What are the main types of composites?
Partuculate, laminated and fiberous.
What are the three main types of properties of engineering materials?
Physical, chemical, and mechanical.
What are physical properties?
Physical properties can be observed or measured without changing the composition of matter.
What are some examples of physical properties?
- Color
- Melting point
- Boiling point
- Density
- Mass
- Conductivity
- Specific gravity
- Fluidity
- Elasticity
- Plasticity
- Porosity
What is specific gravity?
Ratio of density of material with respect to density of reference material or substance
What is fluidity?
Fluidity is defined as the nature that concrete mixtures, under the influence of self-weight and mechanical vibration, start to flow and fill every corner of the
mold-board evenly and densely.
What is elasticity?
Elasticity is the ability of an object or material to resume its normal shape after being stretched or compressed – reversible deformation.
What is plasticity?
Quality of being easily shaped or molded - irreversible deformation.
What is porosity?
Porosity of materials represents quantity of voids in solid materials.
What are mechanical properties?
The mechanical properties of a material are those properties that involve a reaction to an
applied load.
What are some examples of mechanical properties?
Strength, ductility, hardness, impact resistance, fracture toughness.
What is strength?
Strength is the ability of a material to resist deformation caused by external load.
What is ductility?
Ductility is defined as the extent to which a material can be deformed plastically.
