Metals Flashcards
metals - density
metals are generally most dense
stiffness
the resistance to elastic deformation measured in pascals
metals - stiffness
have a high modulus
strength
the resistance to permanent deformation measured in pa
metals -strength
strong but not the strongest
toughness
resistance to cracking, fracture
metals - toughness
are the toughest
metals -thermal conductivity/electrical conductivity
can have much higher conductivity, but not always
metals - cost
metals have a v large range of prices
the strengthening mechanisms
1 atoms in solution, different sizes deflect and create distortions (alloy)
2 dispersion strengthening, adding enough of another element to make a second phase
3 work hardening
4 reduce grain size,more boundaries present , more deflections
casting
pouring a melt into a mould
low cost but can lead to defects
rolling
properties are better if material is deformed - stronger squeezes out pores refines microstructure work hardening good for producing long bits, eg rails
forging
hot softened metal pushed/ flattened into shape
produces good microstructure high strength
extrusions
can produce complex materials
steel needs high temp so not practical method
common for aluminium or polymers
austenite (gamma)
high temp phase
fcc structure
(can be present in stainless steels and non magnetic metals)