Engineering Materials Final Exam

phase

a region in a material that has a uniform structure, properties, and composition and maintains a distinct boundary with other unlike phases

cooling curve

temperature of molten metal vs time as it cools to room temp

hypoeutectic alloys

alloys with Sn wt% greater than 19.2 and less than 61.9

hypereutectic alloys

alloys with Sn wt% greater than 61.9 and less than 97.5

peritectic reaction

liquid phase reacts with a solid phase to form a new and different solid phase

monotectic reaction

liquid phase transforms into solid phase and another liquid

terminal phases

phases that occur at the end of phase diagrams

intermediate phases

phases that occur in a composition range inside phase diagram

pig iron

iron ore mixed with coke inside a blast furnace

austenitizing

eutectoid steel heated slightly abobe 727 C and held there for sufficient time

martensite

a metastable phase consisting of super saturated interstitial solid solution of C in BCC

full anneal heat treatment

softens the steel to its lowest strength and grows large equiaxed grains

process anneal heat treatment

relieves the internal residual stresses through realignment of dislocations

normalization heat treatment

refines the grain structure, produces a stronger steel

precipitation strengthening heat treatments

creates fine dispersion of precipitated particles in the metal which hinder dislocation

steps: solution heat treatment, quenching, aging

properties of aluminum

low density, corrosion resistance, high alloy strength, nontoxic, and good electrical properties

properties of Copper

good electrical and thermal conduction, ease of fabrication, corrosion resistance, medium strength

properties of stainless steel

excellent corrosion resistance because of chromium oxide surface, high strength and durability, and good heat resistance

cast iron properties

easily melted, very fluid, low shrinkage, easily machinable, low impact resistance and ductility

amorphous metals

atoms arranged in random manner in metals under special circumstances (Ti)

properties of titanium alloys

low density and high strength, expensive, superior corrosion resistance, special technique needed to work with metal, HCP at room temp —> BCC at 883 C

steps of chain polymerization

initiation, propagation, termination

vinyl polymers

one of the hydrogen atoms is replaced by another atom or group of atoms

vinylidene polymers

both hydrogen atoms on the carbon chain are replaced by another atom or group of atoms

homopolymers

polymer chain made up of single repeating units

copolymers

polymer chains made up of two or more repeating units

random copolymers

different monomers randomly arranged in chains (ABBABAAABAA)

alternating copolymers

definite ordered alterations of monomers (ABABABABAB)

block copolymers

different monomers arranged in long blocks (AAAAAABBBBBB)

graft copolymers

one type of monomer grafted to long chain of another

injection molding

plastic granules or pellets are transformed into sheets, rods, sections, etc to manufacture thermoplastic components

injection molding

pros: high quality parts, rapid production rate, low labor cost, good surface finish, highly automated, intricate shapes

cons: high cost of machines, process requires close monitoring and control

extrusion

melted plastic force by rotating screw through a opening and used to produce pipes, rods, etc

blow molding

compressed air is blown into heated cylinder or pipe of plastic to press it against the wall of mold

thermoforming

heated plastic sheet is forced into contours of a mold by pressure

compression molding

preheated thermosetting resins are formed into solid parts

transfer molding

a plunger forces the preheated plastic resin, placed outside mold, into mold cavities for thermosetting plastics

polyethylene

clear whitish translucent thermoplastic

types: low density, high density, linear low density

polyvinylchloride (PVC)

a noon-crystalline or amorphous thermoplastic and doesn’t recrystallize

polypropylene (PP)

third most used thermoplastic and lowest in cost, low density, good chemical resistance, moisture resistance and heat resistance

applications: housewares, appliances, packaging, lab ware, bottles

ABS

high impact applications, mixture of three monomers

applications: pipe and fittings, automotive parts, computer and telephone housings

engineering thermoplastics

low densit, low tensile strength, high insulation, good corrosion resistance

properties of nylons (polyamides)

high strength due to hydrogen bonding, flexibility, low melt viscosity, high lubricity

applications: electrical equipment, gears, auto parts, packaging

polycarbonate (PC)

high strengths, toughness and dimensional stability, very high impact strength, high heat deflection temp, resistance to corrosion

applications: precision parts, cams, gears, helmets, power tool housing

thermosetting plastics

high thermal and dimensional stability , rigidity, resistance to creep, light weight

ceramics

inorganic, nonmetallic, strong ionic or covalent bonds, excellent electrical insulators, excellent heat insulators, very hard, highly brittle, low toughness, high melting temp

graphite

carbon allotrope, layred structue with carbon atoms strongly bonded in hexagonal arrays

properties: high strength and conductivity, excellent lubricating properties

diamond

carbon allotrope, cubic structure

properties: stiffest, hardest, and least compressible material made by nature, high thermal conductivity but minimal electrical conductivity

forming processes of ceramics

pressing, slip casting, and extrusion

slip casting

slip poured into mold, draining mold, dried and fired int mold, top trimmed

extrusion

ceramic precursor is forced through hard steel ot alloy die by a motor divern augur

conventional ceramics

clay, silica, feldspar (potassium)

clay

provides workability and hardness in material

silica (flint quartz)

high melting temp and is refractory component of traditional ceramics

Feldspar or Potash (potassium)

low melting temperature and makes a glass when the ceramic mix is fired.

engineering ceramics

alumina, silicon nitride, silicon carbide, zirconia

mechanical properties of ceramics

generally brittle, tensile strength lower than compressive, less dense than most metals, low toughness, low thermal conductivity, and high heat resistance

composites

pros: light weight —> low density, high strength and stiffness, high specific modulus and specific strength, controlled anisotropy

cons: low ductility, low resistance to impact damage

glass fibers

high strength-to-weight ratio, good dimensional stability, good temp, and corrsion resistant, and low cost

carbon fibers

lightweight with very high strength and stiffness

carbon fiber manufacturing

stabilization, carbonization, graphization

lamina

unidirectional layer of fiber-reinforced polymer, strong and stiff in fiber direction

concrete

flexible, economical, fire resistant, durable, fabricated on site, high compressible but low tensile strength

wood

naturally occurring composite with polymeric material

softwoods

seed is exposed, retain its leaves, and physically soft

hardwoods

seeds are covered, sheds leaves annually