metals and composites Flashcards
the 4 types of engineering materials
metals, ceramics, polymers, composites
4 advantages of metals
high stiffness and strength
toughness
good electrical and thermal conductivity
cost effective
Metals can be {1} for high hardness, strength and {2}
1: alloyed
2: rigidity
what’s meant by toughness
capacity to absorb energy
what material has greater thermal conductivity than respective materials
metals, compared to ceramics and polymers
ferrous metal meaning
based on iron e.g. steel, cast iron
superalloys are based on {1}, nickel or {2}
1: iron
2: cobalt
Alloying can enhance material {1}. Alloying can increase {2} and {3} relative to pure metals.
1:properties
2, 3: strength, hardness
define hardness
ability to withstand surface indentation
alloying is …
mixture/compound of 2+ elements, at least one being metallic
2 main alloying categories
solid solutions
intermediate phases
solid solutions means…
alloy where one element is dissolved in another, forms a single phase structure
what’s meant by a phase
any homogenous mass e.g. metal, in which grains have the same crystal lattice structure
In solid solution, what material is the solvent or base element? What material is the dissolved element
metallic
metallic or non
2 forms of solid solutions, briefly describe
1) substitutional– atoms of solvent element replaced in its unit cell by dissolved element
2) interstitial– atoms of dissolving element fit into vacant spaces between base metal atoms in lattice structure
In both solid solution forms, alloy structure is generally {1} and {2} than either of the component elements
1,2 : stronger, harder
There’s usually limits to the {1} of one element in another. When the amount of {2} element in the alloy exceeds the solid {1} limit of the {3} metal, a {4} phase forms in the alloy. I.e. the chemical composition is {5} between the two {6} elements.
1: solubility
2: dissolving
3: base
4: second
5: intermediate
6: pure
Metallic compounds are an example of {1} phases, consisting of…
1: intermediate
metal and non metal e.g. iron carbide, Fe3C
Intermetallic compounds are …, such as …
two metals forming a compound e.g. Roman yellow brass, CuZn
For intermetallic compounds, describe structure and properties
1) intermetallic–well defined stoichiometry (elements combine in fixed, precise ratios) and ordered crystal structures, form when 2=+ metals combine in specific atomic ratios
properties–high hardness and temp resistance
Intermetallic compounds tend to be more brittle due to their { 1 }. They display unique superconducting, chemical and {2} properties due to their { 3 } and mixed bonding (metallic and {4})
1: more ordered structure
2: magnetic
3: more ordered structure
4: ionic
For metallic compounds, describe structure and properties
mix of 2=+ metals (or metals and another element), where combined metals retain some of their individual properties
more ductile and malleable than intermetallic
varying melting point
designed to harness best properties of constituent metals e.g. improved strength, corrosion resistance
{1} compounds are widely used in various industries due to their customizable properties, such as construction, {2} and {3}
1: metallic
2, 3: aerospace, automotive
Intermetallic compounds are known for their high { 1 } and unique magnetic and chemical properties, they are generally more {2}. Metallic compounds, on the other hand, are valued for their {3}, malleability, and {4} properties.
1: melting points
2: brittle
3: ductility
4: customizable
Two phase alloys are important as they can be { 1 } for much higher strength than { 2 }
1: heat treated
2: solid solutions
eutectic alloy meaning
mixture 2=+ elements that has specific composition st it solidifies at single lower temperature, eutectic point//
solidus and liquidus at same temp
Eutectic, derived from the Greek word eutektos, meaning easily {1}. Eutectic temperature is the { 2 } of the eutectic composition, always the {3} { 2 } for the alloy system.
1: melted
2: melting point
3: lowest
2 most important ferrous metals
alloys of iron and carbon (superior strength)
iron and carbon alloys divided into two major groups:
steel and cast iron, make approx 85% of metal tonnage
For iron, the phase at room temperature is alpha, called {1} which is a BCC/FCC. At {2} degrees, ferrite transforms to gamma, called {3} which is a BCC/FCC. Then from 1394 degrees, this transforms to delta, BCC/FCC.
1: ferrite, BCC
2: 912
3: austenite, FCC
FCC
pure iron melts at
1540 degrees
the most pure iron is {1} iron, at about x%, for research and other purpose where pure metal is required.
1: electrolytic
99.99
{1} iron contains 0.1% impurities, and is used in applications where high {2} or { 3 } is needed
1: ingot
2,3: ductility, corrosion resistance
{1} iron is contains 3% slag, but very little carbon, and is easily shaped in hot forming operations such as {2}
1: wrought
2: forging
Ferrite/Austenite dissolves more carbon than ferrite/austenite. The difference in {1} between alpha and gamma provides opportunities for strengthening via {2} treatment
Austenite, ferrite
solubility
heat
what are superalloys?
High performance alloys designed to meet demanding requirements for strength & resistance to surface degradation at high temps
Many superalloys contain substantial amounts of {1} or more metals, rather than one base metal +alloying elements. Superalloys are very {in/expensive}, and are technologically important due to their { 2 }.
1: 3
2: unique properties
For super alloys, {room/high} temperature performance is good, while {room/high} temp performance is excellent
room, high
For superalloys, {1} temperature performance is excellent - tensile strength, hot hardness,
{c__ & c___} resistance, and at very {1} temperatures
Operating temperatures often ~ {2} ºC.
Applications e.g. {3}, for any system operating more {4} at {5} temperatures
1: high
corrosion, creep
3: jet and rocket engines, steam turbines, and
nuclear power plants
4: efficiently
5: elevated
True or false,
superalloys excel in systems that operate more efficiently at high temperatures
true
three groups of superalloys
iron based e.g. alloyed with Ni
nickel based, better high temp strength than alloy steels, alloyed with Fe, Ti
cobalt based
all superalloys strengthen by { 1 }
precipitation hardening
common process for steel making
basic oxygen furnace
electric furnace
three metal shaping processes
casting, powder metallurgy, deformation, material removal
metal parts are joined to form assemblies by {1, 2 ,3 }
welding, soldering, mechanical fastening
heat {1} is used to enhance properties
treating
finishing processes (e.g. {1} & {2}), are used to improve appearance of metal parts and/or provide { 3 }
1: painting, electroplating
3: corrosion protection
3 methods to enhance metal properties
alloying, cold working, heat treatment
Cold working, involves { 1 } during {2} to increase strength, reduces {3}. Heat treatment involves heating and {4} {5} performed to beneficially change its {6} properties.
1: strain hardening
2: deformation
3: ductility
4: cooling
5: cycles
6: mechanical
heat treatments, cold working and alloying work by altering the metals {1} which in turn determines its {2}
1: microstructure
2: properties
Greatest use in manufacturing for silicon is in ceramics (e.g. {1} in glass and {2} in clays), and alloying elements in e.g. {3}. {4} silicon is of significant technological importance as the base material in {5} manufacturing in electronics.
1: SiO2
2: silicates
3: steel, cast iron, Al, Cu
4: Pure
5: semiconductor
2 basic categories of processing ceramics
molten and particulate
