Materialteknik

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• yield strength describes the transistion from elastic to plastic behaviour
• unit cell unit of the crystal structure that represents its symmetry
• yield strength the intersection of the deformation curve and a line parallel to the elastic portion and offset with 0, 2% on the strain axis
• plastic deformation permanent deformation, plastic region in the non-linear portion of the stress-strain curve, which is when the strain exceeds the elastic limit
• tensile strength maximum stress in the stress-strain curve
• ductility measurement of how much plastic strain a material can take, measured by elongation
• edge dislocation made by cutting, slipping and rejoining bonds across the slip plane
• screw dislocation upper part of crystal is displaced parallel to the edge of the cut rather than normal to it
• recrystallization occurs at elevated temp, stress-free grains nucleate at high-stress areas of the microstructure, grains grow together until they constitut the entire microstructure
• diffusion atomic transformation by atomic motion, needs: an empty site, enough energy to break bonds of neighbour atoms and displace atoms while moving
• self-diffusion host atoms migrate
• vacancy-diffusion vacancy exchanges place with host atom or impurity
• impurity diffusion impurity exchanges place with vacancy
• interstitial diffusion movement of interstitial impurity atom
• interdiffusion diffusion in opposite directions
• steady-state diffusion rate is independent of time, flux proportional to concentration gradient
• equilibrium phase diagram represents the equilibrium condition of a material as a function of temp and composition
• solid solution a solid in which one or more elements are dissolved in another so that they are homogenously dispersed at an atomic scale
• solubility limit composition at which an element no longer will dissolve in another element at given temp
• solubility solute atoms replace host atoms in the lattice
• solubility depends on atomic size factor, crystal structure, electronegativity, valences
• eutec- a normal V meeting a horizontal line
• peritec- an inverted V meeting a horizontal line
• -tic a liquid phase is involved
• -toid all phases are solid
• delta-ferrite BCC, 1394-1534
• austenite, gamma-Fe FCC, 910-1394
• Ferrite, alpha-ferrite BCC, RT-910
• cementite, Fe3C metastable, very hard and brittle
• peritectic reaction 1493, delta+L<-->gamma
• eutectic reaction 1147, L<-->gamma+Fe3C
• Eutectoid reaction 723, gamma<-->alpha+Fe3C
• nucleation local-scale diffusion process, rate decreases with decreasing temp
• martensitic transformation diffusion-less transformation which occurs by a sudden re-orientation of C and Fe atoms from the FCC solid solution to a body-centered tetragonal structure, metastable phase and cannot be found in a phase diagram
• TTT capture the extent of an isothermal transformation as a function of temp and time, depending on the time-temp history the microstructure will differ
• pearlite 400-727
• total energy use of a product the materials, embodied energy, energy of processing, use-energy, maintanance energy, disposal energy
• flip chip bonding small beads of solder are formed on bonding pads on the die, which is then mounted face-fown on the base and heated up until the solder melts and forms a contact between metal tracks on tje base and the bonding pads
• electromigration very high current densities, collisions between electrons and atoms in metallic film->drift of atoms in direction of electron flow
• kirkendall effect 2 species, A and B, are diffusing, B dissolves in A and A dissolves in B, movement of interfaces due to unequal diffusion rates
• electrical resistivity measure of a materials resistance to current passing through it
• electrical conductivity is proportional to the number of free electrons, n, and the mobility of electrons which is proportional to the mean free path
• electrical conductivity is the reverse of resistivity, 1/(resistivity)
• conductors silver, copper, iron (metals)
• semi-conductors silicon, germanium, gats
• insulators glass, concrete, aluminum, polyethylene (ceramics and polymers)
• electron energy band structure conduction band, valence band
• conduction band empty, lowest unoccupied energy level
• valence band filled, highest occupied energy level
• electronic properties of a solid is a result of the band structure, arrangement of the outermost electron bands and if they are filled with electrons
• electrical conductivity, high or low larger band gap, lower conductivity at given temp
• resistivity of metal total resistivity of a metal is the sum of contributions from thermal vibrations, impurities and plastic deformation
• matthiesen's rule Ptot=Pt+Pi+Pd, Pt=temp effect, Pi=impurity effect, Pd=effect due to deformation
• superconductivity at critical temp the resistivity drops to zero, the material becomes a superconductor, once set in motion the electrical current will flow forever in a superconducting material
• intrinsic semiconductor the electrical behaviour is based on the electronic structure inherent to the pure material
• extrinsic semiconductor the electrical behaviour is due to impurity atoms
• heat capacity energy needed to heat 1kg of a material by 1K, the ability of a material to absorb heat, energy required to increase the temp of the material
• thermal expansion thermal strain per degree of temp change
• thermal conductivity rate of which heat is conducted through a solid at steady-state
• mean free path distance a phonon travels before scattering
• thermal shock occurs due to constraint of thermal expansion, occurs due to uneven rapid heating/cooling
• substitutional solid solution dissolved atoms replace those in host material
• interstitial solid solution dissolved atoms squeezes into spaces between host atoms
• carburization carbon atoms diffuse into a material, carbon is an interstitial atom and harden the surface (solution strengthening)
• epitaxy in epitaxial growth, a layer is mimicking the crystal structure of the layers below
• doping adding impurities to a semiconductor, makes material an extrinsic semiconductor
• recovery No major microstructural changes, but dislocations move to lower-energy positions

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