Mate 210 Midterm #2

Heat Capacity

ability of material to absorb heat

molar heat capacity

how much hear it takes to raise 1 mol of material 1 degree celcius

Thermal conductivity

materials response to heat flow, related to heat transfer, higher means heat flows quickly through the material

phonon contribution TC

vibrations moving through a material, large bond energy means large this

electrons TC

carry heat due to mass, if free move heat and contribute to a materials ability to do that

porosity

pockets within something,when vibrations hit a it they scatter disrupting heat trasnfer, the higher amount the lower the thermal conductivity

Thermal stress

occurs when a material experiences temperature changes that cause expansion or contraction, leading to internal forces and potential damage

Thermal shock resistance

like toughness, how much material a material can handle

Material Electrical Conductivity Ranking

Metals > Conductive Ceramics > Polymers and Non-conducitve Ceramics

mobility

how easily a charge can move through a single material

scattering

when an atoms hits an electron causing it to move, sometimes in same direction but often a new one, reducing electrical conductivity

alloying scattering

When there are multiple types of atoms in a metallic alloy, leading to different atom sizes, which causes interruptions to the parallel structure of the material, leading to reduced electrical conductivity

electrical conductivity

the measure of a material's ability to conduct electric current, influenced by factors like temperature and material structure.

free holes

Holes in a semiconductor contribute to electrical conductivity by allowing the movement of positive charge

conductivity band

empty orbitals, free to move

valence band

fully filled orbitals stuck to area

Absorbing Light conductivity enhancement

when light energy = bandgap energy electrons move to CB becoming free and creating a free hole which increases conductivity

Temp Change conductivity enhancement

temp changes n and p exponentially as temperature increases, the number of charge carriers increases, leading to enhanced conductivity. not in metals

Processing Impurities conductivity enhancement

introduced substances that affect charge carrier concentrations and material properties during manufacturing.

Piezo electric effect

mechanical deformation produces voltage,caused by charge inbalance in crystal structure where an E-field is creates and dipoles try to align with voltage making material deform to align

piezoelectric charge coefficient

relationship between volatage and how much a a material deforms, ceramics have highest due to ionic bonding and there is no effect in metals

Curie temp

temp for wether a structure behaves in a piezoelectric manner(assymetry)

solution phase

exists on multiple points of the graph for different matter states of the material

tie line

line of constant temp, determines composition

lever rule

a tool used in materials science and chemistry to determine the relative amounts of phases present in a two-phase region of a phase diagram

slow cooling

diffusion happens such that each phase has uniform distribution

fast cooling

not enough time for diffusion, causing deviated lines of cooling

eutectic structure

has alternating structure of alpha and beta, an alloy structure created from two or more closely adjacent solid phases precipitating simultaneously or alternately from the same homogeneous liquid phase

hypoeutectic microstructure

grains of alpha with beta lines in eutectic

hypereuctectic microstrucure

grains of Beta with eutectic lines of alpha

eutectoid

a specific point on a phase diagram where a solid phase transforms into two or more other solid phases upon cooling.

Solid A → Solid B + Solid C

Carborization

the addition of carbon to metals like steel at surface, where methane is burned into causing hyrogens to pop off and carbon to diffuse into the metal

Pearlite

slow cooling, occurs at .76 weight percent carbon, alternating layers of ferrite and cementite

quenching

the rapid cooling of a metal to adjust the mechanical properties of its original state

martensite

single phase and microstructure that occurs at quenching, not on phase diagram, locks carbon in place, strains that makes it very strong

alloys

metals with other elements added to it

ferrous metal

anything containing iron aka steel, alloys classified by amount of iron

non-ferrous steel

something without iron ie copper, tin, aluminium

steel

ferrous metal with 0 → 1.4 wt% carbon

cast iron

ferrous metal with 3-4.5 wt% carbon

ferrite

phase of steel, solid solution of Iron and Carbon,least carbon. soft and ductile

Austenite

solid solutioin of Iron and carbon, only phase that can transform more when cooled

Cementite

hard,strong,super brittle, only found at 6.7 wt% carbon, pure carbon and lattice

Coarse Pearlite

pearlite that has big grains

Fine Pearlite

pearlite with small grains

Bainite

cools fast but not by quenching, block ferrite with cementite, high strength low ductility

temporing

reheating of material after quenching to alter material properties

galvanizing

dump part into liquid zinc, helps to prevent corrosion

stainless steel

chromium added to Copper and Iron

aging aluminum

a heat treatment used to enhance the mechanical properties of metals, particularly aluminum alloys

tempered martensite

background of ferrite with dots of comentite, achieved by a heat treatment

nucleation

the forming of the crystal of a new phase

phase growth

the expansion of a crystal/phase until it takes over

TTT(Time,Temp,transfer) diagram

diagram used for steps at a constant temperature

CCT(continous cooling transformation) diagram

the cooling rate is shown on this diagram, can show difference between fine vs coarse pearlite

Critical cooling Rate

if cooled caster than it, material will become martensite.Depends on material composition and type