unit 3 Flashcards
what are some qualities of metals and alloys?
-form metallic bonds
-crystaline structure is dense and well ordered
-shiny, malleable, ductile, good conductors of electricity
What are the four forms of metals/alloys in steel production
Ferrite (a) iron is a solid solution of carbon dissolved in BCC
iron.
Austenite (g) iron is a solid solution of carbon dissolved in FCC
iron.
Cementite (Fe3C) is a hard brittle compound of iron and
carbon.
Pearlite is a lamellar compound consisting of a combination of
Ferrite and Cementite.
What is the role of carbon in ferrite and austentite?
the carbon acts as an interstitial
impurity.
what is cold working?
the strengthening of metals during plastic deformation through rolling, forging, extrusion or wire and bar drawing. doing this increases dislocations exponentially, making the dislocations lock up with each other and strengthening the metal.
what is the disadvantage of cold working?
the capacity for plastic deformation decreases, reducing the metal’s ductility
generally yield strength increases, tensile strength increases, ductility decreses.
what are the qualities of magnesium?
lightest metal
used for structural and non structural applications
used in aircraft and missile components
good at vibration dampening
what are the qualities of copper?
resistant to corrosion, wear and tear
good thermal and electrical conductor
‘
used as electronic components, springs, and heat exchangers
BRASS is an alloy of copper and zinc
BRONZE is an alloy of copper and tin
what are the qualities of Nickel?
nickel has high strength, toughness, and corrosion resistance
used in stainless steels and nickel based aloys
nickel alloys used for high temp applications like jet engines and rockets
what are polymers?
Organic (carbon based) materials with long chain like molecular bonds.
natural polymers are cellulose, synthetic polymers are plastics
4 types, linear unbranched linear branched, cross-linked unbranched, cross linked branched
what are thermoplastic polymers?
composed of linear branched or linear unbranched chains
behave in a plastic ductile manner
soften and flow when heated
re-harden when cooled
easily molded
what are thermoset polymers?
long chain (linear or branched) molecules strongly bonded through covalent bonds
harder to recycle than thermoplastics
DO NOT soften when heated, and CANNOT be remelted
heat resistant
stronger that thermoplastics but more brittle
What are some examples of thermosets?
epoxy, polyester, silicone, vulcanized rubber
What are some examples of thermoplastics?
easier to recycle than thermosets
acrylic (plexigass), polythelyne (plastic bottles), polystyrene (styrofoam), polypropylene (plastic containers)
in polymers, what is the relationship between crystallinity and ductility ?
as crystallinity increases, molecular cross links increase and the ductility decreases
what happens as polymers melt?
MELTING: when a polymer melts it goes from solid material with ordered structure of aligned molecular chains into a viscous liquid with random molecular structure
GLASS TRANSITION: polymer goes from a rubbery state (elastic) to a rigid state (brittle)
what are ceramics?
-solids that aren’t metallic or organic
-resist corrosion and high temp,
-low conductivity
-bond types are covalent (SiO2) or ionic (NaCl)
- ceramics are crystalline or amorphous in structure,
- very brittle in failure
what type of ceramic is glass?
-glass is an AMORPHOUS ceramic compound of tetrahedral SiO2+
-has a high melting point,
-can be refractive, reflective, or transparent
-formed from a molten state, formed into different shapes
what are composites?
material made by combining two or more materials that are mutually insoluble. the materials are mixed so that they both maintain their integrity afterwards.
composites can be particle reinforced or fiber reinforced, combined in multiple layers to form laminates
what are the advantages and disadvantages of composites?
advantages:
-high specific strength and specific stiffness
-good corrosion resistance
-can be custom designed for thermal, electrical, and aesthetic qualities
disadvantages
-cost
-difficult to design
-difficult to recycle
-difficult to detect damage
